Date: 2022-03-31T04:47:49+00:00

Actual source code: dt.c

      1: /* Discretization tools */

      3: #include <petscdt.h>
      4: #include <petscblaslapack.h>
      5: #include <petsc/private/petscimpl.h>
      6: #include <petsc/private/dtimpl.h>
      7: #include <petscviewer.h>
      8: #include <petscdmplex.h>
      9: #include <petscdmshell.h>

     11: #if defined(PETSC_HAVE_MPFR)
     12: #include <mpfr.h>
     13: #endif

     15: const char *const PetscDTNodeTypes[] = {"gaussjacobi", "equispaced", "tanhsinh", "PETSCDTNODES_", NULL};

     17: static PetscBool GolubWelschCite       = PETSC_FALSE;
     18: const char       GolubWelschCitation[] = "@article{GolubWelsch1969,\n"
     19:                                          "  author  = {Golub and Welsch},\n"
     20:                                          "  title   = {Calculation of Quadrature Rules},\n"
     21:                                          "  journal = {Math. Comp.},\n"
     22:                                          "  volume  = {23},\n"
     23:                                          "  number  = {106},\n"
     24:                                          "  pages   = {221--230},\n"
     25:                                          "  year    = {1969}\n}\n";

     27: /* Numerical tests in src/dm/dt/tests/ex1.c show that when computing the nodes and weights of Gauss-Jacobi
     28:    quadrature rules:

     30:    - in double precision, Newton's method and Golub & Welsch both work for moderate degrees (< 100),
     31:    - in single precision, Newton's method starts producing incorrect roots around n = 15, but
     32:      the weights from Golub & Welsch become a problem before then: they produces errors
     33:      in computing the Jacobi-polynomial Gram matrix around n = 6.

     35:    So we default to Newton's method (required fewer dependencies) */
     36: PetscBool PetscDTGaussQuadratureNewton_Internal = PETSC_TRUE;

     38: PetscClassId PETSCQUADRATURE_CLASSID = 0;

     40: /*@
     41:   PetscQuadratureCreate - Create a PetscQuadrature object

     43:   Collective

     45:   Input Parameter:
     46: . comm - The communicator for the PetscQuadrature object

     48:   Output Parameter:
     49: . q  - The PetscQuadrature object

     51:   Level: beginner

     53: .seealso: PetscQuadratureDestroy(), PetscQuadratureGetData()
     54: @*/
     55: PetscErrorCode PetscQuadratureCreate(MPI_Comm comm, PetscQuadrature *q)
     56: {
     58:   DMInitializePackage();
     59:   PetscHeaderCreate(*q,PETSCQUADRATURE_CLASSID,"PetscQuadrature","Quadrature","DT",comm,PetscQuadratureDestroy,PetscQuadratureView);
     60:   (*q)->dim       = -1;
     61:   (*q)->Nc        =  1;
     62:   (*q)->order     = -1;
     63:   (*q)->numPoints = 0;
     64:   (*q)->points    = NULL;
     65:   (*q)->weights   = NULL;
     66:   return 0;
     67: }

     69: /*@
     70:   PetscQuadratureDuplicate - Create a deep copy of the PetscQuadrature object

     72:   Collective on q

     74:   Input Parameter:
     75: . q  - The PetscQuadrature object

     77:   Output Parameter:
     78: . r  - The new PetscQuadrature object

     80:   Level: beginner

     82: .seealso: PetscQuadratureCreate(), PetscQuadratureDestroy(), PetscQuadratureGetData()
     83: @*/
     84: PetscErrorCode PetscQuadratureDuplicate(PetscQuadrature q, PetscQuadrature *r)
     85: {
     86:   PetscInt         order, dim, Nc, Nq;
     87:   const PetscReal *points, *weights;
     88:   PetscReal       *p, *w;

     91:   PetscQuadratureCreate(PetscObjectComm((PetscObject) q), r);
     92:   PetscQuadratureGetOrder(q, &order);
     93:   PetscQuadratureSetOrder(*r, order);
     94:   PetscQuadratureGetData(q, &dim, &Nc, &Nq, &points, &weights);
     95:   PetscMalloc1(Nq*dim, &p);
     96:   PetscMalloc1(Nq*Nc, &w);
     97:   PetscArraycpy(p, points, Nq*dim);
     98:   PetscArraycpy(w, weights, Nc * Nq);
     99:   PetscQuadratureSetData(*r, dim, Nc, Nq, p, w);
    100:   return 0;
    101: }

    103: /*@
    104:   PetscQuadratureDestroy - Destroys a PetscQuadrature object

    106:   Collective on q

    108:   Input Parameter:
    109: . q  - The PetscQuadrature object

    111:   Level: beginner

    113: .seealso: PetscQuadratureCreate(), PetscQuadratureGetData()
    114: @*/
    115: PetscErrorCode PetscQuadratureDestroy(PetscQuadrature *q)
    116: {
    117:   if (!*q) return 0;
    119:   if (--((PetscObject)(*q))->refct > 0) {
    120:     *q = NULL;
    121:     return 0;
    122:   }
    123:   PetscFree((*q)->points);
    124:   PetscFree((*q)->weights);
    125:   PetscHeaderDestroy(q);
    126:   return 0;
    127: }

    129: /*@
    130:   PetscQuadratureGetOrder - Return the order of the method

    132:   Not collective

    134:   Input Parameter:
    135: . q - The PetscQuadrature object

    137:   Output Parameter:
    138: . order - The order of the quadrature, i.e. the highest degree polynomial that is exactly integrated

    140:   Level: intermediate

    142: .seealso: PetscQuadratureSetOrder(), PetscQuadratureGetData(), PetscQuadratureSetData()
    143: @*/
    144: PetscErrorCode PetscQuadratureGetOrder(PetscQuadrature q, PetscInt *order)
    145: {
    148:   *order = q->order;
    149:   return 0;
    150: }

    152: /*@
    153:   PetscQuadratureSetOrder - Return the order of the method

    155:   Not collective

    157:   Input Parameters:
    158: + q - The PetscQuadrature object
    159: - order - The order of the quadrature, i.e. the highest degree polynomial that is exactly integrated

    161:   Level: intermediate

    163: .seealso: PetscQuadratureGetOrder(), PetscQuadratureGetData(), PetscQuadratureSetData()
    164: @*/
    165: PetscErrorCode PetscQuadratureSetOrder(PetscQuadrature q, PetscInt order)
    166: {
    168:   q->order = order;
    169:   return 0;
    170: }

    172: /*@
    173:   PetscQuadratureGetNumComponents - Return the number of components for functions to be integrated

    175:   Not collective

    177:   Input Parameter:
    178: . q - The PetscQuadrature object

    180:   Output Parameter:
    181: . Nc - The number of components

    183:   Note: We are performing an integral int f(x) . w(x) dx, where both f and w (the weight) have Nc components.

    185:   Level: intermediate

    187: .seealso: PetscQuadratureSetNumComponents(), PetscQuadratureGetData(), PetscQuadratureSetData()
    188: @*/
    189: PetscErrorCode PetscQuadratureGetNumComponents(PetscQuadrature q, PetscInt *Nc)
    190: {
    193:   *Nc = q->Nc;
    194:   return 0;
    195: }

    197: /*@
    198:   PetscQuadratureSetNumComponents - Return the number of components for functions to be integrated

    200:   Not collective

    202:   Input Parameters:
    203: + q  - The PetscQuadrature object
    204: - Nc - The number of components

    206:   Note: We are performing an integral int f(x) . w(x) dx, where both f and w (the weight) have Nc components.

    208:   Level: intermediate

    210: .seealso: PetscQuadratureGetNumComponents(), PetscQuadratureGetData(), PetscQuadratureSetData()
    211: @*/
    212: PetscErrorCode PetscQuadratureSetNumComponents(PetscQuadrature q, PetscInt Nc)
    213: {
    215:   q->Nc = Nc;
    216:   return 0;
    217: }

    219: /*@C
    220:   PetscQuadratureGetData - Returns the data defining the quadrature

    222:   Not collective

    224:   Input Parameter:
    225: . q  - The PetscQuadrature object

    227:   Output Parameters:
    228: + dim - The spatial dimension
    229: . Nc - The number of components
    230: . npoints - The number of quadrature points
    231: . points - The coordinates of each quadrature point
    232: - weights - The weight of each quadrature point

    234:   Level: intermediate

    236:   Fortran Notes:
    237:     From Fortran you must call PetscQuadratureRestoreData() when you are done with the data

    239: .seealso: PetscQuadratureCreate(), PetscQuadratureSetData()
    240: @*/
    241: PetscErrorCode PetscQuadratureGetData(PetscQuadrature q, PetscInt *dim, PetscInt *Nc, PetscInt *npoints, const PetscReal *points[], const PetscReal *weights[])
    242: {
    244:   if (dim) {
    246:     *dim = q->dim;
    247:   }
    248:   if (Nc) {
    250:     *Nc = q->Nc;
    251:   }
    252:   if (npoints) {
    254:     *npoints = q->numPoints;
    255:   }
    256:   if (points) {
    258:     *points = q->points;
    259:   }
    260:   if (weights) {
    262:     *weights = q->weights;
    263:   }
    264:   return 0;
    265: }

    267: /*@
    268:   PetscQuadratureEqual - determine whether two quadratures are equivalent

    270:   Input Parameters:
    271: + A - A PetscQuadrature object
    272: - B - Another PetscQuadrature object

    274:   Output Parameters:
    275: . equal - PETSC_TRUE if the quadratures are the same

    277:   Level: intermediate

    279: .seealso: PetscQuadratureCreate()
    280: @*/
    281: PetscErrorCode PetscQuadratureEqual(PetscQuadrature A, PetscQuadrature B, PetscBool *equal)
    282: {
    286:   *equal = PETSC_FALSE;
    287:   if (A->dim != B->dim || A->Nc != B->Nc || A->order != B->order || A->numPoints != B->numPoints) {
    288:     return 0;
    289:   }
    290:   for (PetscInt i=0; i<A->numPoints*A->dim; i++) {
    291:     if (PetscAbsReal(A->points[i] - B->points[i]) > PETSC_SMALL) {
    292:       return 0;
    293:     }
    294:   }
    295:   if (!A->weights && !B->weights) {
    296:     *equal = PETSC_TRUE;
    297:     return 0;
    298:   }
    299:   if (A->weights && B->weights) {
    300:     for (PetscInt i=0; i<A->numPoints; i++) {
    301:       if (PetscAbsReal(A->weights[i] - B->weights[i]) > PETSC_SMALL) {
    302:         return 0;
    303:       }
    304:     }
    305:     *equal = PETSC_TRUE;
    306:   }
    307:   return 0;
    308: }

    310: static PetscErrorCode PetscDTJacobianInverse_Internal(PetscInt m, PetscInt n, const PetscReal J[], PetscReal Jinv[])
    311: {
    312:   PetscScalar    *Js, *Jinvs;
    313:   PetscInt       i, j, k;
    314:   PetscBLASInt   bm, bn, info;

    316:   if (!m || !n) return 0;
    317:   PetscBLASIntCast(m, &bm);
    318:   PetscBLASIntCast(n, &bn);
    319: #if defined(PETSC_USE_COMPLEX)
    320:   PetscMalloc2(m*n, &Js, m*n, &Jinvs);
    321:   for (i = 0; i < m*n; i++) Js[i] = J[i];
    322: #else
    323:   Js = (PetscReal *) J;
    324:   Jinvs = Jinv;
    325: #endif
    326:   if (m == n) {
    327:     PetscBLASInt *pivots;
    328:     PetscScalar *W;

    330:     PetscMalloc2(m, &pivots, m, &W);

    332:     PetscArraycpy(Jinvs, Js, m * m);
    333:     PetscStackCallBLAS("LAPACKgetrf", LAPACKgetrf_(&bm, &bm, Jinvs, &bm, pivots, &info));
    335:     PetscStackCallBLAS("LAPACKgetri", LAPACKgetri_(&bm, Jinvs, &bm, pivots, W, &bm, &info));
    337:     PetscFree2(pivots, W);
    338:   } else if (m < n) {
    339:     PetscScalar *JJT;
    340:     PetscBLASInt *pivots;
    341:     PetscScalar *W;

    343:     PetscMalloc1(m*m, &JJT);
    344:     PetscMalloc2(m, &pivots, m, &W);
    345:     for (i = 0; i < m; i++) {
    346:       for (j = 0; j < m; j++) {
    347:         PetscScalar val = 0.;

    349:         for (k = 0; k < n; k++) val += Js[i * n + k] * Js[j * n + k];
    350:         JJT[i * m + j] = val;
    351:       }
    352:     }

    354:     PetscStackCallBLAS("LAPACKgetrf", LAPACKgetrf_(&bm, &bm, JJT, &bm, pivots, &info));
    356:     PetscStackCallBLAS("LAPACKgetri", LAPACKgetri_(&bm, JJT, &bm, pivots, W, &bm, &info));
    358:     for (i = 0; i < n; i++) {
    359:       for (j = 0; j < m; j++) {
    360:         PetscScalar val = 0.;

    362:         for (k = 0; k < m; k++) val += Js[k * n + i] * JJT[k * m + j];
    363:         Jinvs[i * m + j] = val;
    364:       }
    365:     }
    366:     PetscFree2(pivots, W);
    367:     PetscFree(JJT);
    368:   } else {
    369:     PetscScalar *JTJ;
    370:     PetscBLASInt *pivots;
    371:     PetscScalar *W;

    373:     PetscMalloc1(n*n, &JTJ);
    374:     PetscMalloc2(n, &pivots, n, &W);
    375:     for (i = 0; i < n; i++) {
    376:       for (j = 0; j < n; j++) {
    377:         PetscScalar val = 0.;

    379:         for (k = 0; k < m; k++) val += Js[k * n + i] * Js[k * n + j];
    380:         JTJ[i * n + j] = val;
    381:       }
    382:     }

    384:     PetscStackCallBLAS("LAPACKgetrf", LAPACKgetrf_(&bn, &bn, JTJ, &bn, pivots, &info));
    386:     PetscStackCallBLAS("LAPACKgetri", LAPACKgetri_(&bn, JTJ, &bn, pivots, W, &bn, &info));
    388:     for (i = 0; i < n; i++) {
    389:       for (j = 0; j < m; j++) {
    390:         PetscScalar val = 0.;

    392:         for (k = 0; k < n; k++) val += JTJ[i * n + k] * Js[j * n + k];
    393:         Jinvs[i * m + j] = val;
    394:       }
    395:     }
    396:     PetscFree2(pivots, W);
    397:     PetscFree(JTJ);
    398:   }
    399: #if defined(PETSC_USE_COMPLEX)
    400:   for (i = 0; i < m*n; i++) Jinv[i] = PetscRealPart(Jinvs[i]);
    401:   PetscFree2(Js, Jinvs);
    402: #endif
    403:   return 0;
    404: }

    406: /*@
    407:    PetscQuadraturePushForward - Push forward a quadrature functional under an affine transformation.

    409:    Collecive on PetscQuadrature

    411:    Input Parameters:
    412: +  q - the quadrature functional
    413: .  imageDim - the dimension of the image of the transformation
    414: .  origin - a point in the original space
    415: .  originImage - the image of the origin under the transformation
    416: .  J - the Jacobian of the image: an [imageDim x dim] matrix in row major order
    417: -  formDegree - transform the quadrature weights as k-forms of this form degree (if the number of components is a multiple of (dim choose formDegree), it is assumed that they represent multiple k-forms) [see PetscDTAltVPullback() for interpretation of formDegree]

    419:    Output Parameters:
    420: .  Jinvstarq - a quadrature rule where each point is the image of a point in the original quadrature rule, and where the k-form weights have been pulled-back by the pseudoinverse of J to the k-form weights in the image space.

    422:    Note: the new quadrature rule will have a different number of components if spaces have different dimensions.  For example, pushing a 2-form forward from a two dimensional space to a three dimensional space changes the number of components from 1 to 3.

    424:    Level: intermediate

    426: .seealso: PetscDTAltVPullback(), PetscDTAltVPullbackMatrix()
    427: @*/
    428: PetscErrorCode PetscQuadraturePushForward(PetscQuadrature q, PetscInt imageDim, const PetscReal origin[], const PetscReal originImage[], const PetscReal J[], PetscInt formDegree, PetscQuadrature *Jinvstarq)
    429: {
    430:   PetscInt         dim, Nc, imageNc, formSize, Ncopies, imageFormSize, Npoints, pt, i, j, c;
    431:   const PetscReal *points;
    432:   const PetscReal *weights;
    433:   PetscReal       *imagePoints, *imageWeights;
    434:   PetscReal       *Jinv;
    435:   PetscReal       *Jinvstar;

    439:   PetscQuadratureGetData(q, &dim, &Nc, &Npoints, &points, &weights);
    440:   PetscDTBinomialInt(dim, PetscAbsInt(formDegree), &formSize);
    442:   Ncopies = Nc / formSize;
    443:   PetscDTBinomialInt(imageDim, PetscAbsInt(formDegree), &imageFormSize);
    444:   imageNc = Ncopies * imageFormSize;
    445:   PetscMalloc1(Npoints * imageDim, &imagePoints);
    446:   PetscMalloc1(Npoints * imageNc, &imageWeights);
    447:   PetscMalloc2(imageDim * dim, &Jinv, formSize * imageFormSize, &Jinvstar);
    448:   PetscDTJacobianInverse_Internal(imageDim, dim, J, Jinv);
    449:   PetscDTAltVPullbackMatrix(imageDim, dim, Jinv, formDegree, Jinvstar);
    450:   for (pt = 0; pt < Npoints; pt++) {
    451:     const PetscReal *point = &points[pt * dim];
    452:     PetscReal       *imagePoint = &imagePoints[pt * imageDim];

    454:     for (i = 0; i < imageDim; i++) {
    455:       PetscReal val = originImage[i];

    457:       for (j = 0; j < dim; j++) val += J[i * dim + j] * (point[j] - origin[j]);
    458:       imagePoint[i] = val;
    459:     }
    460:     for (c = 0; c < Ncopies; c++) {
    461:       const PetscReal *form = &weights[pt * Nc + c * formSize];
    462:       PetscReal       *imageForm = &imageWeights[pt * imageNc + c * imageFormSize];

    464:       for (i = 0; i < imageFormSize; i++) {
    465:         PetscReal val = 0.;

    467:         for (j = 0; j < formSize; j++) val += Jinvstar[i * formSize + j] * form[j];
    468:         imageForm[i] = val;
    469:       }
    470:     }
    471:   }
    472:   PetscQuadratureCreate(PetscObjectComm((PetscObject)q), Jinvstarq);
    473:   PetscQuadratureSetData(*Jinvstarq, imageDim, imageNc, Npoints, imagePoints, imageWeights);
    474:   PetscFree2(Jinv, Jinvstar);
    475:   return 0;
    476: }

    478: /*@C
    479:   PetscQuadratureSetData - Sets the data defining the quadrature

    481:   Not collective

    483:   Input Parameters:
    484: + q  - The PetscQuadrature object
    485: . dim - The spatial dimension
    486: . Nc - The number of components
    487: . npoints - The number of quadrature points
    488: . points - The coordinates of each quadrature point
    489: - weights - The weight of each quadrature point

    491:   Note: This routine owns the references to points and weights, so they must be allocated using PetscMalloc() and the user should not free them.

    493:   Level: intermediate

    495: .seealso: PetscQuadratureCreate(), PetscQuadratureGetData()
    496: @*/
    497: PetscErrorCode PetscQuadratureSetData(PetscQuadrature q, PetscInt dim, PetscInt Nc, PetscInt npoints, const PetscReal points[], const PetscReal weights[])
    498: {
    500:   if (dim >= 0)     q->dim       = dim;
    501:   if (Nc >= 0)      q->Nc        = Nc;
    502:   if (npoints >= 0) q->numPoints = npoints;
    503:   if (points) {
    505:     q->points = points;
    506:   }
    507:   if (weights) {
    509:     q->weights = weights;
    510:   }
    511:   return 0;
    512: }

    514: static PetscErrorCode PetscQuadratureView_Ascii(PetscQuadrature quad, PetscViewer v)
    515: {
    516:   PetscInt          q, d, c;
    517:   PetscViewerFormat format;

    519:   if (quad->Nc > 1) PetscViewerASCIIPrintf(v, "Quadrature of order %D on %D points (dim %D) with %D components\n", quad->order, quad->numPoints, quad->dim, quad->Nc);
    520:   else              PetscViewerASCIIPrintf(v, "Quadrature of order %D on %D points (dim %D)\n", quad->order, quad->numPoints, quad->dim);
    521:   PetscViewerGetFormat(v, &format);
    522:   if (format != PETSC_VIEWER_ASCII_INFO_DETAIL) return 0;
    523:   for (q = 0; q < quad->numPoints; ++q) {
    524:     PetscViewerASCIIPrintf(v, "p%D (", q);
    525:     PetscViewerASCIIUseTabs(v, PETSC_FALSE);
    526:     for (d = 0; d < quad->dim; ++d) {
    527:       if (d) PetscViewerASCIIPrintf(v, ", ");
    528:       PetscViewerASCIIPrintf(v, "%+g", (double)quad->points[q*quad->dim+d]);
    529:     }
    530:     PetscViewerASCIIPrintf(v, ") ");
    531:     if (quad->Nc > 1) PetscViewerASCIIPrintf(v, "w%D (", q);
    532:     for (c = 0; c < quad->Nc; ++c) {
    533:       if (c) PetscViewerASCIIPrintf(v, ", ");
    534:       PetscViewerASCIIPrintf(v, "%+g", (double)quad->weights[q*quad->Nc+c]);
    535:     }
    536:     if (quad->Nc > 1) PetscViewerASCIIPrintf(v, ")");
    537:     PetscViewerASCIIPrintf(v, "\n");
    538:     PetscViewerASCIIUseTabs(v, PETSC_TRUE);
    539:   }
    540:   return 0;
    541: }

    543: /*@C
    544:   PetscQuadratureView - Views a PetscQuadrature object

    546:   Collective on quad

    548:   Input Parameters:
    549: + quad  - The PetscQuadrature object
    550: - viewer - The PetscViewer object

    552:   Level: beginner

    554: .seealso: PetscQuadratureCreate(), PetscQuadratureGetData()
    555: @*/
    556: PetscErrorCode PetscQuadratureView(PetscQuadrature quad, PetscViewer viewer)
    557: {
    558:   PetscBool      iascii;

    562:   if (!viewer) PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject) quad), &viewer);
    563:   PetscObjectTypeCompare((PetscObject) viewer, PETSCVIEWERASCII, &iascii);
    564:   PetscViewerASCIIPushTab(viewer);
    565:   if (iascii) PetscQuadratureView_Ascii(quad, viewer);
    566:   PetscViewerASCIIPopTab(viewer);
    567:   return 0;
    568: }

    570: /*@C
    571:   PetscQuadratureExpandComposite - Return a quadrature over the composite element, which has the original quadrature in each subelement

    573:   Not collective

    575:   Input Parameters:
    576: + q - The original PetscQuadrature
    577: . numSubelements - The number of subelements the original element is divided into
    578: . v0 - An array of the initial points for each subelement
    579: - jac - An array of the Jacobian mappings from the reference to each subelement

    581:   Output Parameters:
    582: . dim - The dimension

    584:   Note: Together v0 and jac define an affine mapping from the original reference element to each subelement

    586:  Not available from Fortran

    588:   Level: intermediate

    590: .seealso: PetscFECreate(), PetscSpaceGetDimension(), PetscDualSpaceGetDimension()
    591: @*/
    592: PetscErrorCode PetscQuadratureExpandComposite(PetscQuadrature q, PetscInt numSubelements, const PetscReal v0[], const PetscReal jac[], PetscQuadrature *qref)
    593: {
    594:   const PetscReal *points,    *weights;
    595:   PetscReal       *pointsRef, *weightsRef;
    596:   PetscInt         dim, Nc, order, npoints, npointsRef, c, p, cp, d, e;

    602:   PetscQuadratureCreate(PETSC_COMM_SELF, qref);
    603:   PetscQuadratureGetOrder(q, &order);
    604:   PetscQuadratureGetData(q, &dim, &Nc, &npoints, &points, &weights);
    605:   npointsRef = npoints*numSubelements;
    606:   PetscMalloc1(npointsRef*dim,&pointsRef);
    607:   PetscMalloc1(npointsRef*Nc, &weightsRef);
    608:   for (c = 0; c < numSubelements; ++c) {
    609:     for (p = 0; p < npoints; ++p) {
    610:       for (d = 0; d < dim; ++d) {
    611:         pointsRef[(c*npoints + p)*dim+d] = v0[c*dim+d];
    612:         for (e = 0; e < dim; ++e) {
    613:           pointsRef[(c*npoints + p)*dim+d] += jac[(c*dim + d)*dim+e]*(points[p*dim+e] + 1.0);
    614:         }
    615:       }
    616:       /* Could also use detJ here */
    617:       for (cp = 0; cp < Nc; ++cp) weightsRef[(c*npoints+p)*Nc+cp] = weights[p*Nc+cp]/numSubelements;
    618:     }
    619:   }
    620:   PetscQuadratureSetOrder(*qref, order);
    621:   PetscQuadratureSetData(*qref, dim, Nc, npointsRef, pointsRef, weightsRef);
    622:   return 0;
    623: }

    625: /* Compute the coefficients for the Jacobi polynomial recurrence,
    626:  *
    627:  * J^{a,b}_n(x) = (cnm1 + cnm1x * x) * J^{a,b}_{n-1}(x) - cnm2 * J^{a,b}_{n-2}(x).
    628:  */
    629: #define PetscDTJacobiRecurrence_Internal(n,a,b,cnm1,cnm1x,cnm2) \
    630: do {                                                            \
    631:   PetscReal _a = (a);                                           \
    632:   PetscReal _b = (b);                                           \
    633:   PetscReal _n = (n);                                           \
    634:   if (n == 1) {                                                 \
    635:     (cnm1) = (_a-_b) * 0.5;                                     \
    636:     (cnm1x) = (_a+_b+2.)*0.5;                                   \
    637:     (cnm2) = 0.;                                                \
    638:   } else {                                                      \
    639:     PetscReal _2n = _n+_n;                                      \
    640:     PetscReal _d = (_2n*(_n+_a+_b)*(_2n+_a+_b-2));              \
    641:     PetscReal _n1 = (_2n+_a+_b-1.)*(_a*_a-_b*_b);               \
    642:     PetscReal _n1x = (_2n+_a+_b-1.)*(_2n+_a+_b)*(_2n+_a+_b-2);  \
    643:     PetscReal _n2 = 2.*((_n+_a-1.)*(_n+_b-1.)*(_2n+_a+_b));     \
    644:     (cnm1) = _n1 / _d;                                          \
    645:     (cnm1x) = _n1x / _d;                                        \
    646:     (cnm2) = _n2 / _d;                                          \
    647:   }                                                             \
    648: } while (0)

    650: /*@
    651:   PetscDTJacobiNorm - Compute the weighted L2 norm of a Jacobi polynomial.

    653:   $\| P^{\alpha,\beta}_n \|_{\alpha,\beta}^2 = \int_{-1}^1 (1 + x)^{\alpha} (1 - x)^{\beta} P^{\alpha,\beta}_n (x)^2 dx.$

    655:   Input Parameters:
    656: - alpha - the left exponent > -1
    657: . beta - the right exponent > -1
    658: + n - the polynomial degree

    660:   Output Parameter:
    661: . norm - the weighted L2 norm

    663:   Level: beginner

    665: .seealso: PetscDTJacobiEval()
    666: @*/
    667: PetscErrorCode PetscDTJacobiNorm(PetscReal alpha, PetscReal beta, PetscInt n, PetscReal *norm)
    668: {
    669:   PetscReal twoab1;
    670:   PetscReal gr;

    675:   twoab1 = PetscPowReal(2., alpha + beta + 1.);
    676: #if defined(PETSC_HAVE_LGAMMA)
    677:   if (!n) {
    678:     gr = PetscExpReal(PetscLGamma(alpha+1.) + PetscLGamma(beta+1.) - PetscLGamma(alpha+beta+2.));
    679:   } else {
    680:     gr = PetscExpReal(PetscLGamma(n+alpha+1.) + PetscLGamma(n+beta+1.) - (PetscLGamma(n+1.) + PetscLGamma(n+alpha+beta+1.))) / (n+n+alpha+beta+1.);
    681:   }
    682: #else
    683:   {
    684:     PetscInt alphai = (PetscInt) alpha;
    685:     PetscInt betai = (PetscInt) beta;
    686:     PetscInt i;

    688:     gr = n ? (1. / (n+n+alpha+beta+1.)) : 1.;
    689:     if ((PetscReal) alphai == alpha) {
    690:       if (!n) {
    691:         for (i = 0; i < alphai; i++) gr *= (i+1.) / (beta+i+1.);
    692:         gr /= (alpha+beta+1.);
    693:       } else {
    694:         for (i = 0; i < alphai; i++) gr *= (n+i+1.) / (n+beta+i+1.);
    695:       }
    696:     } else if ((PetscReal) betai == beta) {
    697:       if (!n) {
    698:         for (i = 0; i < betai; i++) gr *= (i+1.) / (alpha+i+2.);
    699:         gr /= (alpha+beta+1.);
    700:       } else {
    701:         for (i = 0; i < betai; i++) gr *= (n+i+1.) / (n+alpha+i+1.);
    702:       }
    703:     } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"lgamma() - math routine is unavailable.");
    704:   }
    705: #endif
    706:   *norm = PetscSqrtReal(twoab1 * gr);
    707:   return 0;
    708: }

    710: static PetscErrorCode PetscDTJacobiEval_Internal(PetscInt npoints, PetscReal a, PetscReal b, PetscInt k, const PetscReal *points, PetscInt ndegree, const PetscInt *degrees, PetscReal *p)
    711: {
    712:   PetscReal ak, bk;
    713:   PetscReal abk1;
    714:   PetscInt i,l,maxdegree;

    716:   maxdegree = degrees[ndegree-1] - k;
    717:   ak = a + k;
    718:   bk = b + k;
    719:   abk1 = a + b + k + 1.;
    720:   if (maxdegree < 0) {
    721:     for (i = 0; i < npoints; i++) for (l = 0; l < ndegree; l++) p[i*ndegree+l] = 0.;
    722:     return 0;
    723:   }
    724:   for (i=0; i<npoints; i++) {
    725:     PetscReal pm1,pm2,x;
    726:     PetscReal cnm1, cnm1x, cnm2;
    727:     PetscInt  j,m;

    729:     x    = points[i];
    730:     pm2  = 1.;
    731:     PetscDTJacobiRecurrence_Internal(1,ak,bk,cnm1,cnm1x,cnm2);
    732:     pm1 = (cnm1 + cnm1x*x);
    733:     l    = 0;
    734:     while (l < ndegree && degrees[l] - k < 0) {
    735:       p[l++] = 0.;
    736:     }
    737:     while (l < ndegree && degrees[l] - k == 0) {
    738:       p[l] = pm2;
    739:       for (m = 0; m < k; m++) p[l] *= (abk1 + m) * 0.5;
    740:       l++;
    741:     }
    742:     while (l < ndegree && degrees[l] - k == 1) {
    743:       p[l] = pm1;
    744:       for (m = 0; m < k; m++) p[l] *= (abk1 + 1 + m) * 0.5;
    745:       l++;
    746:     }
    747:     for (j=2; j<=maxdegree; j++) {
    748:       PetscReal pp;

    750:       PetscDTJacobiRecurrence_Internal(j,ak,bk,cnm1,cnm1x,cnm2);
    751:       pp   = (cnm1 + cnm1x*x)*pm1 - cnm2*pm2;
    752:       pm2  = pm1;
    753:       pm1  = pp;
    754:       while (l < ndegree && degrees[l] - k == j) {
    755:         p[l] = pp;
    756:         for (m = 0; m < k; m++) p[l] *= (abk1 + j + m) * 0.5;
    757:         l++;
    758:       }
    759:     }
    760:     p += ndegree;
    761:   }
    762:   return 0;
    763: }

    765: /*@
    766:   PetscDTJacobiEvalJet - Evaluate the jet (function and derivatives) of the Jacobi polynomials basis up to a given degree.  The Jacobi polynomials with indices $\alpha$ and $\beta$ are orthogonal with respect to the weighted inner product $\langle f, g \rangle = \int_{-1}^1 (1+x)^{\alpha} (1-x)^{\beta) f(x) g(x) dx$.

    768:   Input Parameters:
    769: + alpha - the left exponent of the weight
    770: . beta - the right exponetn of the weight
    771: . npoints - the number of points to evaluate the polynomials at
    772: . points - [npoints] array of point coordinates
    773: . degree - the maximm degree polynomial space to evaluate, (degree + 1) will be evaluated total.
    774: - k - the maximum derivative to evaluate in the jet, (k + 1) will be evaluated total.

    776:   Output Argments:
    777: - p - an array containing the evaluations of the Jacobi polynomials's jets on the points.  the size is (degree + 1) x
    778:   (k + 1) x npoints, which also describes the order of the dimensions of this three-dimensional array: the first
    779:   (slowest varying) dimension is polynomial degree; the second dimension is derivative order; the third (fastest
    780:   varying) dimension is the index of the evaluation point.

    782:   Level: advanced

    784: .seealso: PetscDTJacobiEval(), PetscDTPKDEvalJet()
    785: @*/
    786: PetscErrorCode PetscDTJacobiEvalJet(PetscReal alpha, PetscReal beta, PetscInt npoints, const PetscReal points[], PetscInt degree, PetscInt k, PetscReal p[])
    787: {
    788:   PetscInt        i, j, l;
    789:   PetscInt       *degrees;
    790:   PetscReal      *psingle;

    792:   if (degree == 0) {
    793:     PetscInt zero = 0;

    795:     for (i = 0; i <= k; i++) {
    796:       PetscDTJacobiEval_Internal(npoints, alpha, beta, i, points, 1, &zero, &p[i*npoints]);
    797:     }
    798:     return 0;
    799:   }
    800:   PetscMalloc1(degree + 1, &degrees);
    801:   PetscMalloc1((degree + 1) * npoints, &psingle);
    802:   for (i = 0; i <= degree; i++) degrees[i] = i;
    803:   for (i = 0; i <= k; i++) {
    804:     PetscDTJacobiEval_Internal(npoints, alpha, beta, i, points, degree + 1, degrees, psingle);
    805:     for (j = 0; j <= degree; j++) {
    806:       for (l = 0; l < npoints; l++) {
    807:         p[(j * (k + 1) + i) * npoints + l] = psingle[l * (degree + 1) + j];
    808:       }
    809:     }
    810:   }
    811:   PetscFree(psingle);
    812:   PetscFree(degrees);
    813:   return 0;
    814: }

    816: /*@
    817:    PetscDTJacobiEval - evaluate Jacobi polynomials for the weight function $(1.+x)^{\alpha} (1.-x)^{\beta}$
    818:                        at points

    820:    Not Collective

    822:    Input Parameters:
    823: +  npoints - number of spatial points to evaluate at
    824: .  alpha - the left exponent > -1
    825: .  beta - the right exponent > -1
    826: .  points - array of locations to evaluate at
    827: .  ndegree - number of basis degrees to evaluate
    828: -  degrees - sorted array of degrees to evaluate

    830:    Output Parameters:
    831: +  B - row-oriented basis evaluation matrix B[point*ndegree + degree] (dimension npoints*ndegrees, allocated by caller) (or NULL)
    832: .  D - row-oriented derivative evaluation matrix (or NULL)
    833: -  D2 - row-oriented second derivative evaluation matrix (or NULL)

    835:    Level: intermediate

    837: .seealso: PetscDTGaussQuadrature()
    838: @*/
    839: PetscErrorCode PetscDTJacobiEval(PetscInt npoints,PetscReal alpha, PetscReal beta, const PetscReal *points,PetscInt ndegree,const PetscInt *degrees,PetscReal *B,PetscReal *D,PetscReal *D2)
    840: {
    843:   if (!npoints || !ndegree) return 0;
    844:   if (B)  PetscDTJacobiEval_Internal(npoints, alpha, beta, 0, points, ndegree, degrees, B);
    845:   if (D)  PetscDTJacobiEval_Internal(npoints, alpha, beta, 1, points, ndegree, degrees, D);
    846:   if (D2) PetscDTJacobiEval_Internal(npoints, alpha, beta, 2, points, ndegree, degrees, D2);
    847:   return 0;
    848: }

    850: /*@
    851:    PetscDTLegendreEval - evaluate Legendre polynomials at points

    853:    Not Collective

    855:    Input Parameters:
    856: +  npoints - number of spatial points to evaluate at
    857: .  points - array of locations to evaluate at
    858: .  ndegree - number of basis degrees to evaluate
    859: -  degrees - sorted array of degrees to evaluate

    861:    Output Parameters:
    862: +  B - row-oriented basis evaluation matrix B[point*ndegree + degree] (dimension npoints*ndegrees, allocated by caller) (or NULL)
    863: .  D - row-oriented derivative evaluation matrix (or NULL)
    864: -  D2 - row-oriented second derivative evaluation matrix (or NULL)

    866:    Level: intermediate

    868: .seealso: PetscDTGaussQuadrature()
    869: @*/
    870: PetscErrorCode PetscDTLegendreEval(PetscInt npoints,const PetscReal *points,PetscInt ndegree,const PetscInt *degrees,PetscReal *B,PetscReal *D,PetscReal *D2)
    871: {
    872:   PetscDTJacobiEval(npoints, 0., 0., points, ndegree, degrees, B, D, D2);
    873:   return 0;
    874: }

    876: /*@
    877:   PetscDTIndexToGradedOrder - convert an index into a tuple of monomial degrees in a graded order (that is, if the degree sum of tuple x is less than the degree sum of tuple y, then the index of x is smaller than the index of y)

    879:   Input Parameters:
    880: + len - the desired length of the degree tuple
    881: - index - the index to convert: should be >= 0

    883:   Output Parameter:
    884: . degtup - will be filled with a tuple of degrees

    886:   Level: beginner

    888:   Note: for two tuples x and y with the same degree sum, partial degree sums over the final elements of the tuples
    889:   acts as a tiebreaker.  For example, (2, 1, 1) and (1, 2, 1) have the same degree sum, but the degree sum over the
    890:   last two elements is smaller for the former, so (2, 1, 1) < (1, 2, 1).

    892: .seealso: PetscDTGradedOrderToIndex()
    893: @*/
    894: PetscErrorCode PetscDTIndexToGradedOrder(PetscInt len, PetscInt index, PetscInt degtup[])
    895: {
    896:   PetscInt i, total;
    897:   PetscInt sum;

    902:   total = 1;
    903:   sum = 0;
    904:   while (index >= total) {
    905:     index -= total;
    906:     total = (total * (len + sum)) / (sum + 1);
    907:     sum++;
    908:   }
    909:   for (i = 0; i < len; i++) {
    910:     PetscInt c;

    912:     degtup[i] = sum;
    913:     for (c = 0, total = 1; c < sum; c++) {
    914:       /* going into the loop, total is the number of way to have a tuple of sum exactly c with length len - 1 - i */
    915:       if (index < total) break;
    916:       index -= total;
    917:       total = (total * (len - 1 - i + c)) / (c + 1);
    918:       degtup[i]--;
    919:     }
    920:     sum -= degtup[i];
    921:   }
    922:   return 0;
    923: }

    925: /*@
    926:   PetscDTGradedOrderToIndex - convert a tuple into an index in a graded order, the inverse of PetscDTIndexToGradedOrder().

    928:   Input Parameters:
    929: + len - the length of the degree tuple
    930: - degtup - tuple with this length

    932:   Output Parameter:
    933: . index - index in graded order: >= 0

    935:   Level: Beginner

    937:   Note: for two tuples x and y with the same degree sum, partial degree sums over the final elements of the tuples
    938:   acts as a tiebreaker.  For example, (2, 1, 1) and (1, 2, 1) have the same degree sum, but the degree sum over the
    939:   last two elements is smaller for the former, so (2, 1, 1) < (1, 2, 1).

    941: .seealso: PetscDTIndexToGradedOrder()
    942: @*/
    943: PetscErrorCode PetscDTGradedOrderToIndex(PetscInt len, const PetscInt degtup[], PetscInt *index)
    944: {
    945:   PetscInt i, idx, sum, total;

    949:   for (i = 0, sum = 0; i < len; i++) sum += degtup[i];
    950:   idx = 0;
    951:   total = 1;
    952:   for (i = 0; i < sum; i++) {
    953:     idx += total;
    954:     total = (total * (len + i)) / (i + 1);
    955:   }
    956:   for (i = 0; i < len - 1; i++) {
    957:     PetscInt c;

    959:     total = 1;
    960:     sum -= degtup[i];
    961:     for (c = 0; c < sum; c++) {
    962:       idx += total;
    963:       total = (total * (len - 1 - i + c)) / (c + 1);
    964:     }
    965:   }
    966:   *index = idx;
    967:   return 0;
    968: }

    970: static PetscBool PKDCite = PETSC_FALSE;
    971: const char       PKDCitation[] = "@article{Kirby2010,\n"
    972:                                  "  title={Singularity-free evaluation of collapsed-coordinate orthogonal polynomials},\n"
    973:                                  "  author={Kirby, Robert C},\n"
    974:                                  "  journal={ACM Transactions on Mathematical Software (TOMS)},\n"
    975:                                  "  volume={37},\n"
    976:                                  "  number={1},\n"
    977:                                  "  pages={1--16},\n"
    978:                                  "  year={2010},\n"
    979:                                  "  publisher={ACM New York, NY, USA}\n}\n";

    981: /*@
    982:   PetscDTPKDEvalJet - Evaluate the jet (function and derivatives) of the Proriol-Koornwinder-Dubiner (PKD) basis for
    983:   the space of polynomials up to a given degree.  The PKD basis is L2-orthonormal on the biunit simplex (which is used
    984:   as the reference element for finite elements in PETSc), which makes it a stable basis to use for evaluating
    985:   polynomials in that domain.

    987:   Input Parameters:
    988: + dim - the number of variables in the multivariate polynomials
    989: . npoints - the number of points to evaluate the polynomials at
    990: . points - [npoints x dim] array of point coordinates
    991: . degree - the degree (sum of degrees on the variables in a monomial) of the polynomial space to evaluate.  There are ((dim + degree) choose dim) polynomials in this space.
    992: - k - the maximum order partial derivative to evaluate in the jet.  There are (dim + k choose dim) partial derivatives
    993:   in the jet.  Choosing k = 0 means to evaluate just the function and no derivatives

    995:   Output Argments:
    996: - p - an array containing the evaluations of the PKD polynomials' jets on the points.  The size is ((dim + degree)
    997:   choose dim) x ((dim + k) choose dim) x npoints, which also describes the order of the dimensions of this
    998:   three-dimensional array: the first (slowest varying) dimension is basis function index; the second dimension is jet
    999:   index; the third (fastest varying) dimension is the index of the evaluation point.

    1001:   Level: advanced

    1003:   Note: The ordering of the basis functions, and the ordering of the derivatives in the jet, both follow the graded
    1004:   ordering of PetscDTIndexToGradedOrder() and PetscDTGradedOrderToIndex().  For example, in 3D, the polynomial with
    1005:   leading monomial x^2,y^0,z^1, which has degree tuple (2,0,1), which by PetscDTGradedOrderToIndex() has index 12 (it is the 13th basis function in the space);
    1006:   the partial derivative $\partial_x \partial_z$ has order tuple (1,0,1), appears at index 6 in the jet (it is the 7th partial derivative in the jet).

    1008:   The implementation uses Kirby's singularity-free evaluation algorithm, https://doi.org/10.1145/1644001.1644006.

    1010: .seealso: PetscDTGradedOrderToIndex(), PetscDTIndexToGradedOrder(), PetscDTJacobiEvalJet()
    1011: @*/
    1012: PetscErrorCode PetscDTPKDEvalJet(PetscInt dim, PetscInt npoints, const PetscReal points[], PetscInt degree, PetscInt k, PetscReal p[])
    1013: {
    1014:   PetscInt        degidx, kidx, d, pt;
    1015:   PetscInt        Nk, Ndeg;
    1016:   PetscInt       *ktup, *degtup;
    1017:   PetscReal      *scales, initscale, scaleexp;

    1019:   PetscCitationsRegister(PKDCitation, &PKDCite);
    1020:   PetscDTBinomialInt(dim + k, k, &Nk);
    1021:   PetscDTBinomialInt(degree + dim, degree, &Ndeg);
    1022:   PetscMalloc2(dim, &degtup, dim, &ktup);
    1023:   PetscMalloc1(Ndeg, &scales);
    1024:   initscale = 1.;
    1025:   if (dim > 1) {
    1026:     PetscDTBinomial(dim,2,&scaleexp);
    1027:     initscale = PetscPowReal(2.,scaleexp*0.5);
    1028:   }
    1029:   for (degidx = 0; degidx < Ndeg; degidx++) {
    1030:     PetscInt e, i;
    1031:     PetscInt m1idx = -1, m2idx = -1;
    1032:     PetscInt n;
    1033:     PetscInt degsum;
    1034:     PetscReal alpha;
    1035:     PetscReal cnm1, cnm1x, cnm2;
    1036:     PetscReal norm;

    1038:     PetscDTIndexToGradedOrder(dim, degidx, degtup);
    1039:     for (d = dim - 1; d >= 0; d--) if (degtup[d]) break;
    1040:     if (d < 0) { /* constant is 1 everywhere, all derivatives are zero */
    1041:       scales[degidx] = initscale;
    1042:       for (e = 0; e < dim; e++) {
    1043:         PetscDTJacobiNorm(e,0.,0,&norm);
    1044:         scales[degidx] /= norm;
    1045:       }
    1046:       for (i = 0; i < npoints; i++) p[degidx * Nk * npoints + i] = 1.;
    1047:       for (i = 0; i < (Nk - 1) * npoints; i++) p[(degidx * Nk + 1) * npoints + i] = 0.;
    1048:       continue;
    1049:     }
    1050:     n = degtup[d];
    1051:     degtup[d]--;
    1052:     PetscDTGradedOrderToIndex(dim, degtup, &m1idx);
    1053:     if (degtup[d] > 0) {
    1054:       degtup[d]--;
    1055:       PetscDTGradedOrderToIndex(dim, degtup, &m2idx);
    1056:       degtup[d]++;
    1057:     }
    1058:     degtup[d]++;
    1059:     for (e = 0, degsum = 0; e < d; e++) degsum += degtup[e];
    1060:     alpha = 2 * degsum + d;
    1061:     PetscDTJacobiRecurrence_Internal(n,alpha,0.,cnm1,cnm1x,cnm2);

    1063:     scales[degidx] = initscale;
    1064:     for (e = 0, degsum = 0; e < dim; e++) {
    1065:       PetscInt  f;
    1066:       PetscReal ealpha;
    1067:       PetscReal enorm;

    1069:       ealpha = 2 * degsum + e;
    1070:       for (f = 0; f < degsum; f++) scales[degidx] *= 2.;
    1071:       PetscDTJacobiNorm(ealpha,0.,degtup[e],&enorm);
    1072:       scales[degidx] /= enorm;
    1073:       degsum += degtup[e];
    1074:     }

    1076:     for (pt = 0; pt < npoints; pt++) {
    1077:       /* compute the multipliers */
    1078:       PetscReal thetanm1, thetanm1x, thetanm2;

    1080:       thetanm1x = dim - (d+1) + 2.*points[pt * dim + d];
    1081:       for (e = d+1; e < dim; e++) thetanm1x += points[pt * dim + e];
    1082:       thetanm1x *= 0.5;
    1083:       thetanm1 = (2. - (dim-(d+1)));
    1084:       for (e = d+1; e < dim; e++) thetanm1 -= points[pt * dim + e];
    1085:       thetanm1 *= 0.5;
    1086:       thetanm2 = thetanm1 * thetanm1;

    1088:       for (kidx = 0; kidx < Nk; kidx++) {
    1089:         PetscInt f;

    1091:         PetscDTIndexToGradedOrder(dim, kidx, ktup);
    1092:         /* first sum in the same derivative terms */
    1093:         p[(degidx * Nk + kidx) * npoints + pt] = (cnm1 * thetanm1 + cnm1x * thetanm1x) * p[(m1idx * Nk + kidx) * npoints + pt];
    1094:         if (m2idx >= 0) {
    1095:           p[(degidx * Nk + kidx) * npoints + pt] -= cnm2 * thetanm2 * p[(m2idx * Nk + kidx) * npoints + pt];
    1096:         }

    1098:         for (f = d; f < dim; f++) {
    1099:           PetscInt km1idx, mplty = ktup[f];

    1101:           if (!mplty) continue;
    1102:           ktup[f]--;
    1103:           PetscDTGradedOrderToIndex(dim, ktup, &km1idx);

    1105:           /* the derivative of  cnm1x * thetanm1x  wrt x variable f is 0.5 * cnm1x if f > d otherwise it is cnm1x */
    1106:           /* the derivative of  cnm1  * thetanm1   wrt x variable f is 0 if f == d, otherwise it is -0.5 * cnm1 */
    1107:           /* the derivative of -cnm2  * thetanm2   wrt x variable f is 0 if f == d, otherwise it is cnm2 * thetanm1 */
    1108:           if (f > d) {
    1109:             PetscInt f2;

    1111:             p[(degidx * Nk + kidx) * npoints + pt] += mplty * 0.5 * (cnm1x - cnm1) * p[(m1idx * Nk + km1idx) * npoints + pt];
    1112:             if (m2idx >= 0) {
    1113:               p[(degidx * Nk + kidx) * npoints + pt] += mplty * cnm2 * thetanm1 * p[(m2idx * Nk + km1idx) * npoints + pt];
    1114:               /* second derivatives of -cnm2  * thetanm2   wrt x variable f,f2 is like - 0.5 * cnm2 */
    1115:               for (f2 = f; f2 < dim; f2++) {
    1116:                 PetscInt km2idx, mplty2 = ktup[f2];
    1117:                 PetscInt factor;

    1119:                 if (!mplty2) continue;
    1120:                 ktup[f2]--;
    1121:                 PetscDTGradedOrderToIndex(dim, ktup, &km2idx);

    1123:                 factor = mplty * mplty2;
    1124:                 if (f == f2) factor /= 2;
    1125:                 p[(degidx * Nk + kidx) * npoints + pt] -= 0.5 * factor * cnm2 * p[(m2idx * Nk + km2idx) * npoints + pt];
    1126:                 ktup[f2]++;
    1127:               }
    1128:             }
    1129:           } else {
    1130:             p[(degidx * Nk + kidx) * npoints + pt] += mplty * cnm1x * p[(m1idx * Nk + km1idx) * npoints + pt];
    1131:           }
    1132:           ktup[f]++;
    1133:         }
    1134:       }
    1135:     }
    1136:   }
    1137:   for (degidx = 0; degidx < Ndeg; degidx++) {
    1138:     PetscReal scale = scales[degidx];
    1139:     PetscInt i;

    1141:     for (i = 0; i < Nk * npoints; i++) p[degidx*Nk*npoints + i] *= scale;
    1142:   }
    1143:   PetscFree(scales);
    1144:   PetscFree2(degtup, ktup);
    1145:   return 0;
    1146: }

    1148: /*@
    1149:   PetscDTPTrimmedSize - The size of the trimmed polynomial space of k-forms with a given degree and form degree,
    1150:   which can be evaluated in PetscDTPTrimmedEvalJet().

    1152:   Input Parameters:
    1153: + dim - the number of variables in the multivariate polynomials
    1154: . degree - the degree (sum of degrees on the variables in a monomial) of the trimmed polynomial space.
    1155: - formDegree - the degree of the form

    1157:   Output Argments:
    1158: - size - The number ((dim + degree) choose (dim + formDegree)) x ((degree + formDegree - 1) choose (formDegree))

    1160:   Level: advanced

    1162: .seealso: PetscDTPTrimmedEvalJet()
    1163: @*/
    1164: PetscErrorCode PetscDTPTrimmedSize(PetscInt dim, PetscInt degree, PetscInt formDegree, PetscInt *size)
    1165: {
    1166:   PetscInt       Nrk, Nbpt; // number of trimmed polynomials

    1168:   formDegree = PetscAbsInt(formDegree);
    1169:   PetscDTBinomialInt(degree + dim, degree + formDegree, &Nbpt);
    1170:   PetscDTBinomialInt(degree + formDegree - 1, formDegree, &Nrk);
    1171:   Nbpt *= Nrk;
    1172:   *size = Nbpt;
    1173:   return 0;
    1174: }

    1176: /* there was a reference implementation based on section 4.4 of Arnold, Falk & Winther (acta numerica, 2006), but it
    1177:  * was inferior to this implementation */
    1178: static PetscErrorCode PetscDTPTrimmedEvalJet_Internal(PetscInt dim, PetscInt npoints, const PetscReal points[], PetscInt degree, PetscInt formDegree, PetscInt jetDegree, PetscReal p[])
    1179: {
    1180:   PetscInt       formDegreeOrig = formDegree;
    1181:   PetscBool      formNegative = (formDegreeOrig < 0) ? PETSC_TRUE : PETSC_FALSE;

    1183:   formDegree = PetscAbsInt(formDegreeOrig);
    1184:   if (formDegree == 0) {
    1185:     PetscDTPKDEvalJet(dim, npoints, points, degree, jetDegree, p);
    1186:     return 0;
    1187:   }
    1188:   if (formDegree == dim) {
    1189:     PetscDTPKDEvalJet(dim, npoints, points, degree - 1, jetDegree, p);
    1190:     return 0;
    1191:   }
    1192:   PetscInt Nbpt;
    1193:   PetscDTPTrimmedSize(dim, degree, formDegree, &Nbpt);
    1194:   PetscInt Nf;
    1195:   PetscDTBinomialInt(dim, formDegree, &Nf);
    1196:   PetscInt Nk;
    1197:   PetscDTBinomialInt(dim + jetDegree, dim, &Nk);
    1198:   PetscArrayzero(p, Nbpt * Nf * Nk * npoints);

    1200:   PetscInt Nbpm1; // number of scalar polynomials up to degree - 1;
    1201:   PetscDTBinomialInt(dim + degree - 1, dim, &Nbpm1);
    1202:   PetscReal *p_scalar;
    1203:   PetscMalloc1(Nbpm1 * Nk * npoints, &p_scalar);
    1204:   PetscDTPKDEvalJet(dim, npoints, points, degree - 1, jetDegree, p_scalar);
    1205:   PetscInt total = 0;
    1206:   // First add the full polynomials up to degree - 1 into the basis: take the scalar
    1207:   // and copy one for each form component
    1208:   for (PetscInt i = 0; i < Nbpm1; i++) {
    1209:     const PetscReal *src = &p_scalar[i * Nk * npoints];
    1210:     for (PetscInt f = 0; f < Nf; f++) {
    1211:       PetscReal *dest = &p[(total++ * Nf + f) * Nk * npoints];
    1212:       PetscArraycpy(dest, src, Nk * npoints);
    1213:     }
    1214:   }
    1215:   PetscInt *form_atoms;
    1216:   PetscMalloc1(formDegree + 1, &form_atoms);
    1217:   // construct the interior product pattern
    1218:   PetscInt (*pattern)[3];
    1219:   PetscInt Nf1; // number of formDegree + 1 forms
    1220:   PetscDTBinomialInt(dim, formDegree + 1, &Nf1);
    1221:   PetscInt nnz = Nf1 * (formDegree+1);
    1222:   PetscMalloc1(Nf1 * (formDegree+1), &pattern);
    1223:   PetscDTAltVInteriorPattern(dim, formDegree+1, pattern);
    1224:   PetscReal centroid = (1. - dim) / (dim + 1.);
    1225:   PetscInt *deriv;
    1226:   PetscMalloc1(dim, &deriv);
    1227:   for (PetscInt d = dim; d >= formDegree + 1; d--) {
    1228:     PetscInt Nfd1; // number of formDegree + 1 forms in dimension d that include dx_0
    1229:                    // (equal to the number of formDegree forms in dimension d-1)
    1230:     PetscDTBinomialInt(d - 1, formDegree, &Nfd1);
    1231:     // The number of homogeneous (degree-1) scalar polynomials in d variables
    1232:     PetscInt Nh;
    1233:     PetscDTBinomialInt(d - 1 + degree - 1, d - 1, &Nh);
    1234:     const PetscReal *h_scalar = &p_scalar[(Nbpm1 - Nh) * Nk * npoints];
    1235:     for (PetscInt b = 0; b < Nh; b++) {
    1236:       const PetscReal *h_s = &h_scalar[b * Nk * npoints];
    1237:       for (PetscInt f = 0; f < Nfd1; f++) {
    1238:         // construct all formDegree+1 forms that start with dx_(dim - d) /\ ...
    1239:         form_atoms[0] = dim - d;
    1240:         PetscDTEnumSubset(d-1, formDegree, f, &form_atoms[1]);
    1241:         for (PetscInt i = 0; i < formDegree; i++) {
    1242:           form_atoms[1+i] += form_atoms[0] + 1;
    1243:         }
    1244:         PetscInt f_ind; // index of the resulting form
    1245:         PetscDTSubsetIndex(dim, formDegree + 1, form_atoms, &f_ind);
    1246:         PetscReal *p_f = &p[total++ * Nf * Nk * npoints];
    1247:         for (PetscInt nz = 0; nz < nnz; nz++) {
    1248:           PetscInt i = pattern[nz][0]; // formDegree component
    1249:           PetscInt j = pattern[nz][1]; // (formDegree + 1) component
    1250:           PetscInt v = pattern[nz][2]; // coordinate component
    1251:           PetscReal scale = v < 0 ? -1. : 1.;

    1253:           i = formNegative ? (Nf - 1 - i) : i;
    1254:           scale = (formNegative && (i & 1)) ? -scale : scale;
    1255:           v = v < 0 ? -(v + 1) : v;
    1256:           if (j != f_ind) {
    1257:             continue;
    1258:           }
    1259:           PetscReal *p_i = &p_f[i * Nk * npoints];
    1260:           for (PetscInt jet = 0; jet < Nk; jet++) {
    1261:             const PetscReal *h_jet = &h_s[jet * npoints];
    1262:             PetscReal *p_jet = &p_i[jet * npoints];

    1264:             for (PetscInt pt = 0; pt < npoints; pt++) {
    1265:               p_jet[pt] += scale * h_jet[pt] * (points[pt * dim + v] - centroid);
    1266:             }
    1267:             PetscDTIndexToGradedOrder(dim, jet, deriv);
    1268:             deriv[v]++;
    1269:             PetscReal mult = deriv[v];
    1270:             PetscInt l;
    1271:             PetscDTGradedOrderToIndex(dim, deriv, &l);
    1272:             if (l >= Nk) {
    1273:               continue;
    1274:             }
    1275:             p_jet = &p_i[l * npoints];
    1276:             for (PetscInt pt = 0; pt < npoints; pt++) {
    1277:               p_jet[pt] += scale * mult * h_jet[pt];
    1278:             }
    1279:             deriv[v]--;
    1280:           }
    1281:         }
    1282:       }
    1283:     }
    1284:   }
    1286:   PetscFree(deriv);
    1287:   PetscFree(pattern);
    1288:   PetscFree(form_atoms);
    1289:   PetscFree(p_scalar);
    1290:   return 0;
    1291: }

    1293: /*@
    1294:   PetscDTPTrimmedEvalJet - Evaluate the jet (function and derivatives) of a basis of the trimmed polynomial k-forms up to
    1295:   a given degree.

    1297:   Input Parameters:
    1298: + dim - the number of variables in the multivariate polynomials
    1299: . npoints - the number of points to evaluate the polynomials at
    1300: . points - [npoints x dim] array of point coordinates
    1301: . degree - the degree (sum of degrees on the variables in a monomial) of the trimmed polynomial space to evaluate.
    1302:            There are ((dim + degree) choose (dim + formDegree)) x ((degree + formDegree - 1) choose (formDegree)) polynomials in this space.
    1303:            (You can use PetscDTPTrimmedSize() to compute this size.)
    1304: . formDegree - the degree of the form
    1305: - jetDegree - the maximum order partial derivative to evaluate in the jet.  There are ((dim + jetDegree) choose dim) partial derivatives
    1306:               in the jet.  Choosing jetDegree = 0 means to evaluate just the function and no derivatives

    1308:   Output Argments:
    1309: - p - an array containing the evaluations of the PKD polynomials' jets on the points.  The size is
    1310:       PetscDTPTrimmedSize() x ((dim + formDegree) choose dim) x ((dim + k) choose dim) x npoints,
    1311:       which also describes the order of the dimensions of this
    1312:       four-dimensional array:
    1313:         the first (slowest varying) dimension is basis function index;
    1314:         the second dimension is component of the form;
    1315:         the third dimension is jet index;
    1316:         the fourth (fastest varying) dimension is the index of the evaluation point.

    1318:   Level: advanced

    1320:   Note: The ordering of the basis functions is not graded, so the basis functions are not nested by degree like PetscDTPKDEvalJet().
    1321:         The basis functions are not an L2-orthonormal basis on any particular domain.

    1323:   The implementation is based on the description of the trimmed polynomials up to degree r as
    1324:   the direct sum of polynomials up to degree (r-1) and the Koszul differential applied to
    1325:   homogeneous polynomials of degree (r-1).

    1327: .seealso: PetscDTPKDEvalJet(), PetscDTPTrimmedSize()
    1328: @*/
    1329: PetscErrorCode PetscDTPTrimmedEvalJet(PetscInt dim, PetscInt npoints, const PetscReal points[], PetscInt degree, PetscInt formDegree, PetscInt jetDegree, PetscReal p[])
    1330: {
    1331:   PetscDTPTrimmedEvalJet_Internal(dim, npoints, points, degree, formDegree, jetDegree, p);
    1332:   return 0;
    1333: }

    1335: /* solve the symmetric tridiagonal eigenvalue system, writing the eigenvalues into eigs and the eigenvectors into V
    1336:  * with lds n; diag and subdiag are overwritten */
    1337: static PetscErrorCode PetscDTSymmetricTridiagonalEigensolve(PetscInt n, PetscReal diag[], PetscReal subdiag[],
    1338:                                                             PetscReal eigs[], PetscScalar V[])
    1339: {
    1340:   char jobz = 'V'; /* eigenvalues and eigenvectors */
    1341:   char range = 'A'; /* all eigenvalues will be found */
    1342:   PetscReal VL = 0.; /* ignored because range is 'A' */
    1343:   PetscReal VU = 0.; /* ignored because range is 'A' */
    1344:   PetscBLASInt IL = 0; /* ignored because range is 'A' */
    1345:   PetscBLASInt IU = 0; /* ignored because range is 'A' */
    1346:   PetscReal abstol = 0.; /* unused */
    1347:   PetscBLASInt bn, bm, ldz; /* bm will equal bn on exit */
    1348:   PetscBLASInt *isuppz;
    1349:   PetscBLASInt lwork, liwork;
    1350:   PetscReal workquery;
    1351:   PetscBLASInt  iworkquery;
    1352:   PetscBLASInt *iwork;
    1353:   PetscBLASInt info;
    1354:   PetscReal *work = NULL;

    1356: #if !defined(PETSCDTGAUSSIANQUADRATURE_EIG)
    1357:   SETERRQ(PETSC_COMM_SELF, PETSC_ERR_SUP_SYS, "A LAPACK symmetric tridiagonal eigensolver could not be found");
    1358: #endif
    1359:   PetscBLASIntCast(n, &bn);
    1360:   PetscBLASIntCast(n, &ldz);
    1361: #if !defined(PETSC_MISSING_LAPACK_STEGR)
    1362:   PetscMalloc1(2 * n, &isuppz);
    1363:   lwork = -1;
    1364:   liwork = -1;
    1365:   PetscStackCallBLAS("LAPACKstegr",LAPACKstegr_(&jobz,&range,&bn,diag,subdiag,&VL,&VU,&IL,&IU,&abstol,&bm,eigs,V,&ldz,isuppz,&workquery,&lwork,&iworkquery,&liwork,&info));
    1367:   lwork = (PetscBLASInt) workquery;
    1368:   liwork = (PetscBLASInt) iworkquery;
    1369:   PetscMalloc2(lwork, &work, liwork, &iwork);
    1370:   PetscFPTrapPush(PETSC_FP_TRAP_OFF);
    1371:   PetscStackCallBLAS("LAPACKstegr",LAPACKstegr_(&jobz,&range,&bn,diag,subdiag,&VL,&VU,&IL,&IU,&abstol,&bm,eigs,V,&ldz,isuppz,work,&lwork,iwork,&liwork,&info));
    1372:   PetscFPTrapPop();
    1374:   PetscFree2(work, iwork);
    1375:   PetscFree(isuppz);
    1376: #elif !defined(PETSC_MISSING_LAPACK_STEQR)
    1377:   jobz = 'I'; /* Compute eigenvalues and eigenvectors of the
    1378:                  tridiagonal matrix.  Z is initialized to the identity
    1379:                  matrix. */
    1380:   PetscMalloc1(PetscMax(1,2*n-2),&work);
    1381:   PetscStackCallBLAS("LAPACKsteqr",LAPACKsteqr_("I",&bn,diag,subdiag,V,&ldz,work,&info));
    1382:   PetscFPTrapPop();
    1384:   PetscFree(work);
    1385:   PetscArraycpy(eigs,diag,n);
    1386: #endif
    1387:   return 0;
    1388: }

    1390: /* Formula for the weights at the endpoints (-1 and 1) of Gauss-Lobatto-Jacobi
    1391:  * quadrature rules on the interval [-1, 1] */
    1392: static PetscErrorCode PetscDTGaussLobattoJacobiEndweights_Internal(PetscInt n, PetscReal alpha, PetscReal beta, PetscReal *leftw, PetscReal *rightw)
    1393: {
    1394:   PetscReal twoab1;
    1395:   PetscInt  m = n - 2;
    1396:   PetscReal a = alpha + 1.;
    1397:   PetscReal b = beta + 1.;
    1398:   PetscReal gra, grb;

    1400:   twoab1 = PetscPowReal(2., a + b - 1.);
    1401: #if defined(PETSC_HAVE_LGAMMA)
    1402:   grb = PetscExpReal(2. * PetscLGamma(b+1.) + PetscLGamma(m+1.) + PetscLGamma(m+a+1.) -
    1403:                      (PetscLGamma(m+b+1) + PetscLGamma(m+a+b+1.)));
    1404:   gra = PetscExpReal(2. * PetscLGamma(a+1.) + PetscLGamma(m+1.) + PetscLGamma(m+b+1.) -
    1405:                      (PetscLGamma(m+a+1) + PetscLGamma(m+a+b+1.)));
    1406: #else
    1407:   {
    1408:     PetscInt alphai = (PetscInt) alpha;
    1409:     PetscInt betai = (PetscInt) beta;

    1411:     if ((PetscReal) alphai == alpha && (PetscReal) betai == beta) {
    1412:       PetscReal binom1, binom2;

    1414:       PetscDTBinomial(m+b, b, &binom1);
    1415:       PetscDTBinomial(m+a+b, b, &binom2);
    1416:       grb = 1./ (binom1 * binom2);
    1417:       PetscDTBinomial(m+a, a, &binom1);
    1418:       PetscDTBinomial(m+a+b, a, &binom2);
    1419:       gra = 1./ (binom1 * binom2);
    1420:     } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"lgamma() - math routine is unavailable.");
    1421:   }
    1422: #endif
    1423:   *leftw = twoab1 * grb / b;
    1424:   *rightw = twoab1 * gra / a;
    1425:   return 0;
    1426: }

    1428: /* Evaluates the nth jacobi polynomial with weight parameters a,b at a point x.
    1429:    Recurrence relations implemented from the pseudocode given in Karniadakis and Sherwin, Appendix B */
    1430: static inline PetscErrorCode PetscDTComputeJacobi(PetscReal a, PetscReal b, PetscInt n, PetscReal x, PetscReal *P)
    1431: {
    1432:   PetscReal pn1, pn2;
    1433:   PetscReal cnm1, cnm1x, cnm2;
    1434:   PetscInt  k;

    1436:   if (!n) {*P = 1.0; return 0;}
    1437:   PetscDTJacobiRecurrence_Internal(1,a,b,cnm1,cnm1x,cnm2);
    1438:   pn2 = 1.;
    1439:   pn1 = cnm1 + cnm1x*x;
    1440:   if (n == 1) {*P = pn1; return 0;}
    1441:   *P  = 0.0;
    1442:   for (k = 2; k < n+1; ++k) {
    1443:     PetscDTJacobiRecurrence_Internal(k,a,b,cnm1,cnm1x,cnm2);

    1445:     *P  = (cnm1 + cnm1x*x)*pn1 - cnm2*pn2;
    1446:     pn2 = pn1;
    1447:     pn1 = *P;
    1448:   }
    1449:   return 0;
    1450: }

    1452: /* Evaluates the first derivative of P_{n}^{a,b} at a point x. */
    1453: static inline PetscErrorCode PetscDTComputeJacobiDerivative(PetscReal a, PetscReal b, PetscInt n, PetscReal x, PetscInt k, PetscReal *P)
    1454: {
    1455:   PetscReal      nP;
    1456:   PetscInt       i;

    1458:   *P = 0.0;
    1459:   if (k > n) return 0;
    1460:   PetscDTComputeJacobi(a+k, b+k, n-k, x, &nP);
    1461:   for (i = 0; i < k; i++) nP *= (a + b + n + 1. + i) * 0.5;
    1462:   *P = nP;
    1463:   return 0;
    1464: }

    1466: static PetscErrorCode PetscDTGaussJacobiQuadrature_Newton_Internal(PetscInt npoints, PetscReal a, PetscReal b, PetscReal x[], PetscReal w[])
    1467: {
    1468:   PetscInt       maxIter = 100;
    1469:   PetscReal      eps     = PetscExpReal(0.75 * PetscLogReal(PETSC_MACHINE_EPSILON));
    1470:   PetscReal      a1, a6, gf;
    1471:   PetscInt       k;

    1474:   a1 = PetscPowReal(2.0, a+b+1);
    1475: #if defined(PETSC_HAVE_LGAMMA)
    1476:   {
    1477:     PetscReal a2, a3, a4, a5;
    1478:     a2 = PetscLGamma(a + npoints + 1);
    1479:     a3 = PetscLGamma(b + npoints + 1);
    1480:     a4 = PetscLGamma(a + b + npoints + 1);
    1481:     a5 = PetscLGamma(npoints + 1);
    1482:     gf = PetscExpReal(a2 + a3 - (a4 + a5));
    1483:   }
    1484: #else
    1485:   {
    1486:     PetscInt ia, ib;

    1488:     ia = (PetscInt) a;
    1489:     ib = (PetscInt) b;
    1490:     gf = 1.;
    1491:     if (ia == a && ia >= 0) { /* compute ratio of rising factorals wrt a */
    1492:       for (k = 0; k < ia; k++) gf *= (npoints + 1. + k) / (npoints + b + 1. + k);
    1493:     } else if (b == b && ib >= 0) { /* compute ratio of rising factorials wrt b */
    1494:       for (k = 0; k < ib; k++) gf *= (npoints + 1. + k) / (npoints + a + 1. + k);
    1495:     } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"lgamma() - math routine is unavailable.");
    1496:   }
    1497: #endif

    1499:   a6   = a1 * gf;
    1500:   /* Computes the m roots of P_{m}^{a,b} on [-1,1] by Newton's method with Chebyshev points as initial guesses.
    1501:    Algorithm implemented from the pseudocode given by Karniadakis and Sherwin and Python in FIAT */
    1502:   for (k = 0; k < npoints; ++k) {
    1503:     PetscReal r = PetscCosReal(PETSC_PI * (1. - (4.*k + 3. + 2.*b) / (4.*npoints + 2.*(a + b + 1.)))), dP;
    1504:     PetscInt  j;

    1506:     if (k > 0) r = 0.5 * (r + x[k-1]);
    1507:     for (j = 0; j < maxIter; ++j) {
    1508:       PetscReal s = 0.0, delta, f, fp;
    1509:       PetscInt  i;

    1511:       for (i = 0; i < k; ++i) s = s + 1.0 / (r - x[i]);
    1512:       PetscDTComputeJacobi(a, b, npoints, r, &f);
    1513:       PetscDTComputeJacobiDerivative(a, b, npoints, r, 1, &fp);
    1514:       delta = f / (fp - f * s);
    1515:       r     = r - delta;
    1516:       if (PetscAbsReal(delta) < eps) break;
    1517:     }
    1518:     x[k] = r;
    1519:     PetscDTComputeJacobiDerivative(a, b, npoints, x[k], 1, &dP);
    1520:     w[k] = a6 / (1.0 - PetscSqr(x[k])) / PetscSqr(dP);
    1521:   }
    1522:   return 0;
    1523: }

    1525: /* Compute the diagonals of the Jacobi matrix used in Golub & Welsch algorithms for Gauss-Jacobi
    1526:  * quadrature weight calculations on [-1,1] for exponents (1. + x)^a (1.-x)^b */
    1527: static PetscErrorCode PetscDTJacobiMatrix_Internal(PetscInt nPoints, PetscReal a, PetscReal b, PetscReal *d, PetscReal *s)
    1528: {
    1529:   PetscInt       i;

    1531:   for (i = 0; i < nPoints; i++) {
    1532:     PetscReal A, B, C;

    1534:     PetscDTJacobiRecurrence_Internal(i+1,a,b,A,B,C);
    1535:     d[i] = -A / B;
    1536:     if (i) s[i-1] *= C / B;
    1537:     if (i < nPoints - 1) s[i] = 1. / B;
    1538:   }
    1539:   return 0;
    1540: }

    1542: static PetscErrorCode PetscDTGaussJacobiQuadrature_GolubWelsch_Internal(PetscInt npoints, PetscReal a, PetscReal b, PetscReal *x, PetscReal *w)
    1543: {
    1544:   PetscReal mu0;
    1545:   PetscReal ga, gb, gab;
    1546:   PetscInt i;

    1548:   PetscCitationsRegister(GolubWelschCitation, &GolubWelschCite);

    1550: #if defined(PETSC_HAVE_TGAMMA)
    1551:   ga  = PetscTGamma(a + 1);
    1552:   gb  = PetscTGamma(b + 1);
    1553:   gab = PetscTGamma(a + b + 2);
    1554: #else
    1555:   {
    1556:     PetscInt ia, ib;

    1558:     ia = (PetscInt) a;
    1559:     ib = (PetscInt) b;
    1560:     if (ia == a && ib == b && ia + 1 > 0 && ib + 1 > 0 && ia + ib + 2 > 0) { /* All gamma(x) terms are (x-1)! terms */
    1561:       PetscDTFactorial(ia, &ga);
    1562:       PetscDTFactorial(ib, &gb);
    1563:       PetscDTFactorial(ia + ib + 1, &gb);
    1564:     } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"tgamma() - math routine is unavailable.");
    1565:   }
    1566: #endif
    1567:   mu0 = PetscPowReal(2.,a + b + 1.) * ga * gb / gab;

    1569: #if defined(PETSCDTGAUSSIANQUADRATURE_EIG)
    1570:   {
    1571:     PetscReal *diag, *subdiag;
    1572:     PetscScalar *V;

    1574:     PetscMalloc2(npoints, &diag, npoints, &subdiag);
    1575:     PetscMalloc1(npoints*npoints, &V);
    1576:     PetscDTJacobiMatrix_Internal(npoints, a, b, diag, subdiag);
    1577:     for (i = 0; i < npoints - 1; i++) subdiag[i] = PetscSqrtReal(subdiag[i]);
    1578:     PetscDTSymmetricTridiagonalEigensolve(npoints, diag, subdiag, x, V);
    1579:     for (i = 0; i < npoints; i++) w[i] = PetscSqr(PetscRealPart(V[i * npoints])) * mu0;
    1580:     PetscFree(V);
    1581:     PetscFree2(diag, subdiag);
    1582:   }
    1583: #else
    1584:   SETERRQ(PETSC_COMM_SELF, PETSC_ERR_SUP_SYS, "A LAPACK symmetric tridiagonal eigensolver could not be found");
    1585: #endif
    1586:   { /* As of March 2, 2020, The Sun Performance Library breaks the LAPACK contract for xstegr and xsteqr: the
    1587:        eigenvalues are not guaranteed to be in ascending order.  So we heave a passive aggressive sigh and check that
    1588:        the eigenvalues are sorted */
    1589:     PetscBool sorted;

    1591:     PetscSortedReal(npoints, x, &sorted);
    1592:     if (!sorted) {
    1593:       PetscInt *order, i;
    1594:       PetscReal *tmp;

    1596:       PetscMalloc2(npoints, &order, npoints, &tmp);
    1597:       for (i = 0; i < npoints; i++) order[i] = i;
    1598:       PetscSortRealWithPermutation(npoints, x, order);
    1599:       PetscArraycpy(tmp, x, npoints);
    1600:       for (i = 0; i < npoints; i++) x[i] = tmp[order[i]];
    1601:       PetscArraycpy(tmp, w, npoints);
    1602:       for (i = 0; i < npoints; i++) w[i] = tmp[order[i]];
    1603:       PetscFree2(order, tmp);
    1604:     }
    1605:   }
    1606:   return 0;
    1607: }

    1609: static PetscErrorCode PetscDTGaussJacobiQuadrature_Internal(PetscInt npoints,PetscReal alpha, PetscReal beta, PetscReal x[], PetscReal w[], PetscBool newton)
    1610: {
    1612:   /* If asking for a 1D Lobatto point, just return the non-Lobatto 1D point */

    1616:   if (newton) {
    1617:     PetscDTGaussJacobiQuadrature_Newton_Internal(npoints, alpha, beta, x, w);
    1618:   } else {
    1619:     PetscDTGaussJacobiQuadrature_GolubWelsch_Internal(npoints, alpha, beta, x, w);
    1620:   }
    1621:   if (alpha == beta) { /* symmetrize */
    1622:     PetscInt i;
    1623:     for (i = 0; i < (npoints + 1) / 2; i++) {
    1624:       PetscInt  j  = npoints - 1 - i;
    1625:       PetscReal xi = x[i];
    1626:       PetscReal xj = x[j];
    1627:       PetscReal wi = w[i];
    1628:       PetscReal wj = w[j];

    1630:       x[i] = (xi - xj) / 2.;
    1631:       x[j] = (xj - xi) / 2.;
    1632:       w[i] = w[j] = (wi + wj) / 2.;
    1633:     }
    1634:   }
    1635:   return 0;
    1636: }

    1638: /*@
    1639:   PetscDTGaussJacobiQuadrature - quadrature for the interval [a, b] with the weight function
    1640:   $(x-a)^\alpha (x-b)^\beta$.

    1642:   Not collective

    1644:   Input Parameters:
    1645: + npoints - the number of points in the quadrature rule
    1646: . a - the left endpoint of the interval
    1647: . b - the right endpoint of the interval
    1648: . alpha - the left exponent
    1649: - beta - the right exponent

    1651:   Output Parameters:
    1652: + x - array of length npoints, the locations of the quadrature points
    1653: - w - array of length npoints, the weights of the quadrature points

    1655:   Level: intermediate

    1657:   Note: this quadrature rule is exact for polynomials up to degree 2*npoints - 1.
    1658: @*/
    1659: PetscErrorCode PetscDTGaussJacobiQuadrature(PetscInt npoints,PetscReal a, PetscReal b, PetscReal alpha, PetscReal beta, PetscReal x[], PetscReal w[])
    1660: {
    1661:   PetscInt       i;

    1663:   PetscDTGaussJacobiQuadrature_Internal(npoints, alpha, beta, x, w, PetscDTGaussQuadratureNewton_Internal);
    1664:   if (a != -1. || b != 1.) { /* shift */
    1665:     for (i = 0; i < npoints; i++) {
    1666:       x[i] = (x[i] + 1.) * ((b - a) / 2.) + a;
    1667:       w[i] *= (b - a) / 2.;
    1668:     }
    1669:   }
    1670:   return 0;
    1671: }

    1673: static PetscErrorCode PetscDTGaussLobattoJacobiQuadrature_Internal(PetscInt npoints,PetscReal alpha, PetscReal beta, PetscReal x[], PetscReal w[], PetscBool newton)
    1674: {
    1675:   PetscInt       i;

    1678:   /* If asking for a 1D Lobatto point, just return the non-Lobatto 1D point */

    1682:   x[0] = -1.;
    1683:   x[npoints-1] = 1.;
    1684:   if (npoints > 2) {
    1685:     PetscDTGaussJacobiQuadrature_Internal(npoints-2, alpha+1., beta+1., &x[1], &w[1], newton);
    1686:   }
    1687:   for (i = 1; i < npoints - 1; i++) {
    1688:     w[i] /= (1. - x[i]*x[i]);
    1689:   }
    1690:   PetscDTGaussLobattoJacobiEndweights_Internal(npoints, alpha, beta, &w[0], &w[npoints-1]);
    1691:   return 0;
    1692: }

    1694: /*@
    1695:   PetscDTGaussLobattoJacobiQuadrature - quadrature for the interval [a, b] with the weight function
    1696:   $(x-a)^\alpha (x-b)^\beta$, with endpoints a and b included as quadrature points.

    1698:   Not collective

    1700:   Input Parameters:
    1701: + npoints - the number of points in the quadrature rule
    1702: . a - the left endpoint of the interval
    1703: . b - the right endpoint of the interval
    1704: . alpha - the left exponent
    1705: - beta - the right exponent

    1707:   Output Parameters:
    1708: + x - array of length npoints, the locations of the quadrature points
    1709: - w - array of length npoints, the weights of the quadrature points

    1711:   Level: intermediate

    1713:   Note: this quadrature rule is exact for polynomials up to degree 2*npoints - 3.
    1714: @*/
    1715: PetscErrorCode PetscDTGaussLobattoJacobiQuadrature(PetscInt npoints,PetscReal a, PetscReal b, PetscReal alpha, PetscReal beta, PetscReal x[], PetscReal w[])
    1716: {
    1717:   PetscInt       i;

    1719:   PetscDTGaussLobattoJacobiQuadrature_Internal(npoints, alpha, beta, x, w, PetscDTGaussQuadratureNewton_Internal);
    1720:   if (a != -1. || b != 1.) { /* shift */
    1721:     for (i = 0; i < npoints; i++) {
    1722:       x[i] = (x[i] + 1.) * ((b - a) / 2.) + a;
    1723:       w[i] *= (b - a) / 2.;
    1724:     }
    1725:   }
    1726:   return 0;
    1727: }

    1729: /*@
    1730:    PetscDTGaussQuadrature - create Gauss-Legendre quadrature

    1732:    Not Collective

    1734:    Input Parameters:
    1735: +  npoints - number of points
    1736: .  a - left end of interval (often-1)
    1737: -  b - right end of interval (often +1)

    1739:    Output Parameters:
    1740: +  x - quadrature points
    1741: -  w - quadrature weights

    1743:    Level: intermediate

    1745:    References:
    1746: .  * - Golub and Welsch, Calculation of Quadrature Rules, Math. Comp. 23(106), 1969.

    1748: .seealso: PetscDTLegendreEval()
    1749: @*/
    1750: PetscErrorCode PetscDTGaussQuadrature(PetscInt npoints,PetscReal a,PetscReal b,PetscReal *x,PetscReal *w)
    1751: {
    1752:   PetscInt       i;

    1754:   PetscDTGaussJacobiQuadrature_Internal(npoints, 0., 0., x, w, PetscDTGaussQuadratureNewton_Internal);
    1755:   if (a != -1. || b != 1.) { /* shift */
    1756:     for (i = 0; i < npoints; i++) {
    1757:       x[i] = (x[i] + 1.) * ((b - a) / 2.) + a;
    1758:       w[i] *= (b - a) / 2.;
    1759:     }
    1760:   }
    1761:   return 0;
    1762: }

    1764: /*@C
    1765:    PetscDTGaussLobattoLegendreQuadrature - creates a set of the locations and weights of the Gauss-Lobatto-Legendre
    1766:                       nodes of a given size on the domain [-1,1]

    1768:    Not Collective

    1770:    Input Parameters:
    1771: +  n - number of grid nodes
    1772: -  type - PETSCGAUSSLOBATTOLEGENDRE_VIA_LINEAR_ALGEBRA or PETSCGAUSSLOBATTOLEGENDRE_VIA_NEWTON

    1774:    Output Parameters:
    1775: +  x - quadrature points
    1776: -  w - quadrature weights

    1778:    Notes:
    1779:     For n > 30  the Newton approach computes duplicate (incorrect) values for some nodes because the initial guess is apparently not
    1780:           close enough to the desired solution

    1782:    These are useful for implementing spectral methods based on Gauss-Lobatto-Legendre (GLL) nodes

    1784:    See  https://epubs.siam.org/doi/abs/10.1137/110855442  https://epubs.siam.org/doi/abs/10.1137/120889873 for better ways to compute GLL nodes

    1786:    Level: intermediate

    1788: .seealso: PetscDTGaussQuadrature()

    1790: @*/
    1791: PetscErrorCode PetscDTGaussLobattoLegendreQuadrature(PetscInt npoints,PetscGaussLobattoLegendreCreateType type,PetscReal *x,PetscReal *w)
    1792: {
    1793:   PetscBool      newton;

    1796:   newton = (PetscBool) (type == PETSCGAUSSLOBATTOLEGENDRE_VIA_NEWTON);
    1797:   PetscDTGaussLobattoJacobiQuadrature_Internal(npoints, 0., 0., x, w, newton);
    1798:   return 0;
    1799: }

    1801: /*@
    1802:   PetscDTGaussTensorQuadrature - creates a tensor-product Gauss quadrature

    1804:   Not Collective

    1806:   Input Parameters:
    1807: + dim     - The spatial dimension
    1808: . Nc      - The number of components
    1809: . npoints - number of points in one dimension
    1810: . a       - left end of interval (often-1)
    1811: - b       - right end of interval (often +1)

    1813:   Output Parameter:
    1814: . q - A PetscQuadrature object

    1816:   Level: intermediate

    1818: .seealso: PetscDTGaussQuadrature(), PetscDTLegendreEval()
    1819: @*/
    1820: PetscErrorCode PetscDTGaussTensorQuadrature(PetscInt dim, PetscInt Nc, PetscInt npoints, PetscReal a, PetscReal b, PetscQuadrature *q)
    1821: {
    1822:   PetscInt       totpoints = dim > 1 ? dim > 2 ? npoints*PetscSqr(npoints) : PetscSqr(npoints) : npoints, i, j, k, c;
    1823:   PetscReal     *x, *w, *xw, *ww;

    1825:   PetscMalloc1(totpoints*dim,&x);
    1826:   PetscMalloc1(totpoints*Nc,&w);
    1827:   /* Set up the Golub-Welsch system */
    1828:   switch (dim) {
    1829:   case 0:
    1830:     PetscFree(x);
    1831:     PetscFree(w);
    1832:     PetscMalloc1(1, &x);
    1833:     PetscMalloc1(Nc, &w);
    1834:     x[0] = 0.0;
    1835:     for (c = 0; c < Nc; ++c) w[c] = 1.0;
    1836:     break;
    1837:   case 1:
    1838:     PetscMalloc1(npoints,&ww);
    1839:     PetscDTGaussQuadrature(npoints, a, b, x, ww);
    1840:     for (i = 0; i < npoints; ++i) for (c = 0; c < Nc; ++c) w[i*Nc+c] = ww[i];
    1841:     PetscFree(ww);
    1842:     break;
    1843:   case 2:
    1844:     PetscMalloc2(npoints,&xw,npoints,&ww);
    1845:     PetscDTGaussQuadrature(npoints, a, b, xw, ww);
    1846:     for (i = 0; i < npoints; ++i) {
    1847:       for (j = 0; j < npoints; ++j) {
    1848:         x[(i*npoints+j)*dim+0] = xw[i];
    1849:         x[(i*npoints+j)*dim+1] = xw[j];
    1850:         for (c = 0; c < Nc; ++c) w[(i*npoints+j)*Nc+c] = ww[i] * ww[j];
    1851:       }
    1852:     }
    1853:     PetscFree2(xw,ww);
    1854:     break;
    1855:   case 3:
    1856:     PetscMalloc2(npoints,&xw,npoints,&ww);
    1857:     PetscDTGaussQuadrature(npoints, a, b, xw, ww);
    1858:     for (i = 0; i < npoints; ++i) {
    1859:       for (j = 0; j < npoints; ++j) {
    1860:         for (k = 0; k < npoints; ++k) {
    1861:           x[((i*npoints+j)*npoints+k)*dim+0] = xw[i];
    1862:           x[((i*npoints+j)*npoints+k)*dim+1] = xw[j];
    1863:           x[((i*npoints+j)*npoints+k)*dim+2] = xw[k];
    1864:           for (c = 0; c < Nc; ++c) w[((i*npoints+j)*npoints+k)*Nc+c] = ww[i] * ww[j] * ww[k];
    1865:         }
    1866:       }
    1867:     }
    1868:     PetscFree2(xw,ww);
    1869:     break;
    1870:   default:
    1871:     SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Cannot construct quadrature rule for dimension %d", dim);
    1872:   }
    1873:   PetscQuadratureCreate(PETSC_COMM_SELF, q);
    1874:   PetscQuadratureSetOrder(*q, 2*npoints-1);
    1875:   PetscQuadratureSetData(*q, dim, Nc, totpoints, x, w);
    1876:   PetscObjectChangeTypeName((PetscObject)*q,"GaussTensor");
    1877:   return 0;
    1878: }

    1880: /*@
    1881:   PetscDTStroudConicalQuadrature - create Stroud conical quadrature for a simplex

    1883:   Not Collective

    1885:   Input Parameters:
    1886: + dim     - The simplex dimension
    1887: . Nc      - The number of components
    1888: . npoints - The number of points in one dimension
    1889: . a       - left end of interval (often-1)
    1890: - b       - right end of interval (often +1)

    1892:   Output Parameter:
    1893: . q - A PetscQuadrature object

    1895:   Level: intermediate

    1897:   References:
    1898: . * - Karniadakis and Sherwin.  FIAT

    1900:   Note: For dim == 1, this is Gauss-Legendre quadrature

    1902: .seealso: PetscDTGaussTensorQuadrature(), PetscDTGaussQuadrature()
    1903: @*/
    1904: PetscErrorCode PetscDTStroudConicalQuadrature(PetscInt dim, PetscInt Nc, PetscInt npoints, PetscReal a, PetscReal b, PetscQuadrature *q)
    1905: {
    1906:   PetscInt       totprev, totrem;
    1907:   PetscInt       totpoints;
    1908:   PetscReal     *p1, *w1;
    1909:   PetscReal     *x, *w;
    1910:   PetscInt       i, j, k, l, m, pt, c;

    1913:   totpoints = 1;
    1914:   for (i = 0, totpoints = 1; i < dim; i++) totpoints *= npoints;
    1915:   PetscMalloc1(totpoints*dim, &x);
    1916:   PetscMalloc1(totpoints*Nc, &w);
    1917:   PetscMalloc2(npoints, &p1, npoints, &w1);
    1918:   for (i = 0; i < totpoints*Nc; i++) w[i] = 1.;
    1919:   for (i = 0, totprev = 1, totrem = totpoints / npoints; i < dim; i++) {
    1920:     PetscReal mul;

    1922:     mul = PetscPowReal(2.,-i);
    1923:     PetscDTGaussJacobiQuadrature(npoints, -1., 1., i, 0.0, p1, w1);
    1924:     for (pt = 0, l = 0; l < totprev; l++) {
    1925:       for (j = 0; j < npoints; j++) {
    1926:         for (m = 0; m < totrem; m++, pt++) {
    1927:           for (k = 0; k < i; k++) x[pt*dim+k] = (x[pt*dim+k]+1.)*(1.-p1[j])*0.5 - 1.;
    1928:           x[pt * dim + i] = p1[j];
    1929:           for (c = 0; c < Nc; c++) w[pt*Nc + c] *= mul * w1[j];
    1930:         }
    1931:       }
    1932:     }
    1933:     totprev *= npoints;
    1934:     totrem /= npoints;
    1935:   }
    1936:   PetscFree2(p1, w1);
    1937:   PetscQuadratureCreate(PETSC_COMM_SELF, q);
    1938:   PetscQuadratureSetOrder(*q, 2*npoints-1);
    1939:   PetscQuadratureSetData(*q, dim, Nc, totpoints, x, w);
    1940:   PetscObjectChangeTypeName((PetscObject)*q,"StroudConical");
    1941:   return 0;
    1942: }

    1944: /*@
    1945:   PetscDTTanhSinhTensorQuadrature - create tanh-sinh quadrature for a tensor product cell

    1947:   Not Collective

    1949:   Input Parameters:
    1950: + dim   - The cell dimension
    1951: . level - The number of points in one dimension, 2^l
    1952: . a     - left end of interval (often-1)
    1953: - b     - right end of interval (often +1)

    1955:   Output Parameter:
    1956: . q - A PetscQuadrature object

    1958:   Level: intermediate

    1960: .seealso: PetscDTGaussTensorQuadrature()
    1961: @*/
    1962: PetscErrorCode PetscDTTanhSinhTensorQuadrature(PetscInt dim, PetscInt level, PetscReal a, PetscReal b, PetscQuadrature *q)
    1963: {
    1964:   const PetscInt  p     = 16;                        /* Digits of precision in the evaluation */
    1965:   const PetscReal alpha = (b-a)/2.;                  /* Half-width of the integration interval */
    1966:   const PetscReal beta  = (b+a)/2.;                  /* Center of the integration interval */
    1967:   const PetscReal h     = PetscPowReal(2.0, -level); /* Step size, length between x_k */
    1968:   PetscReal       xk;                                /* Quadrature point x_k on reference domain [-1, 1] */
    1969:   PetscReal       wk    = 0.5*PETSC_PI;              /* Quadrature weight at x_k */
    1970:   PetscReal      *x, *w;
    1971:   PetscInt        K, k, npoints;

    1975:   /* Find K such that the weights are < 32 digits of precision */
    1976:   for (K = 1; PetscAbsReal(PetscLog10Real(wk)) < 2*p; ++K) {
    1977:     wk = 0.5*h*PETSC_PI*PetscCoshReal(K*h)/PetscSqr(PetscCoshReal(0.5*PETSC_PI*PetscSinhReal(K*h)));
    1978:   }
    1979:   PetscQuadratureCreate(PETSC_COMM_SELF, q);
    1980:   PetscQuadratureSetOrder(*q, 2*K+1);
    1981:   npoints = 2*K-1;
    1982:   PetscMalloc1(npoints*dim, &x);
    1983:   PetscMalloc1(npoints, &w);
    1984:   /* Center term */
    1985:   x[0] = beta;
    1986:   w[0] = 0.5*alpha*PETSC_PI;
    1987:   for (k = 1; k < K; ++k) {
    1988:     wk = 0.5*alpha*h*PETSC_PI*PetscCoshReal(k*h)/PetscSqr(PetscCoshReal(0.5*PETSC_PI*PetscSinhReal(k*h)));
    1989:     xk = PetscTanhReal(0.5*PETSC_PI*PetscSinhReal(k*h));
    1990:     x[2*k-1] = -alpha*xk+beta;
    1991:     w[2*k-1] = wk;
    1992:     x[2*k+0] =  alpha*xk+beta;
    1993:     w[2*k+0] = wk;
    1994:   }
    1995:   PetscQuadratureSetData(*q, dim, 1, npoints, x, w);
    1996:   return 0;
    1997: }

    1999: PetscErrorCode PetscDTTanhSinhIntegrate(void (*func)(const PetscReal[], void *, PetscReal *), PetscReal a, PetscReal b, PetscInt digits, void *ctx, PetscReal *sol)
    2000: {
    2001:   const PetscInt  p     = 16;        /* Digits of precision in the evaluation */
    2002:   const PetscReal alpha = (b-a)/2.;  /* Half-width of the integration interval */
    2003:   const PetscReal beta  = (b+a)/2.;  /* Center of the integration interval */
    2004:   PetscReal       h     = 1.0;       /* Step size, length between x_k */
    2005:   PetscInt        l     = 0;         /* Level of refinement, h = 2^{-l} */
    2006:   PetscReal       osum  = 0.0;       /* Integral on last level */
    2007:   PetscReal       psum  = 0.0;       /* Integral on the level before the last level */
    2008:   PetscReal       sum;               /* Integral on current level */
    2009:   PetscReal       yk;                /* Quadrature point 1 - x_k on reference domain [-1, 1] */
    2010:   PetscReal       lx, rx;            /* Quadrature points to the left and right of 0 on the real domain [a, b] */
    2011:   PetscReal       wk;                /* Quadrature weight at x_k */
    2012:   PetscReal       lval, rval;        /* Terms in the quadature sum to the left and right of 0 */
    2013:   PetscInt        d;                 /* Digits of precision in the integral */

    2016:   /* Center term */
    2017:   func(&beta, ctx, &lval);
    2018:   sum = 0.5*alpha*PETSC_PI*lval;
    2019:   /* */
    2020:   do {
    2021:     PetscReal lterm, rterm, maxTerm = 0.0, d1, d2, d3, d4;
    2022:     PetscInt  k = 1;

    2024:     ++l;
    2025:     /* PetscPrintf(PETSC_COMM_SELF, "LEVEL %D sum: %15.15f\n", l, sum); */
    2026:     /* At each level of refinement, h --> h/2 and sum --> sum/2 */
    2027:     psum = osum;
    2028:     osum = sum;
    2029:     h   *= 0.5;
    2030:     sum *= 0.5;
    2031:     do {
    2032:       wk = 0.5*h*PETSC_PI*PetscCoshReal(k*h)/PetscSqr(PetscCoshReal(0.5*PETSC_PI*PetscSinhReal(k*h)));
    2033:       yk = 1.0/(PetscExpReal(0.5*PETSC_PI*PetscSinhReal(k*h)) * PetscCoshReal(0.5*PETSC_PI*PetscSinhReal(k*h)));
    2034:       lx = -alpha*(1.0 - yk)+beta;
    2035:       rx =  alpha*(1.0 - yk)+beta;
    2036:       func(&lx, ctx, &lval);
    2037:       func(&rx, ctx, &rval);
    2038:       lterm   = alpha*wk*lval;
    2039:       maxTerm = PetscMax(PetscAbsReal(lterm), maxTerm);
    2040:       sum    += lterm;
    2041:       rterm   = alpha*wk*rval;
    2042:       maxTerm = PetscMax(PetscAbsReal(rterm), maxTerm);
    2043:       sum    += rterm;
    2044:       ++k;
    2045:       /* Only need to evaluate every other point on refined levels */
    2046:       if (l != 1) ++k;
    2047:     } while (PetscAbsReal(PetscLog10Real(wk)) < p); /* Only need to evaluate sum until weights are < 32 digits of precision */

    2049:     d1 = PetscLog10Real(PetscAbsReal(sum - osum));
    2050:     d2 = PetscLog10Real(PetscAbsReal(sum - psum));
    2051:     d3 = PetscLog10Real(maxTerm) - p;
    2052:     if (PetscMax(PetscAbsReal(lterm), PetscAbsReal(rterm)) == 0.0) d4 = 0.0;
    2053:     else d4 = PetscLog10Real(PetscMax(PetscAbsReal(lterm), PetscAbsReal(rterm)));
    2054:     d  = PetscAbsInt(PetscMin(0, PetscMax(PetscMax(PetscMax(PetscSqr(d1)/d2, 2*d1), d3), d4)));
    2055:   } while (d < digits && l < 12);
    2056:   *sol = sum;

    2058:   return 0;
    2059: }

    2061: #if defined(PETSC_HAVE_MPFR)
    2062: PetscErrorCode PetscDTTanhSinhIntegrateMPFR(void (*func)(const PetscReal[], void *, PetscReal *), PetscReal a, PetscReal b, PetscInt digits, void *ctx, PetscReal *sol)
    2063: {
    2064:   const PetscInt  safetyFactor = 2;  /* Calculate abcissa until 2*p digits */
    2065:   PetscInt        l            = 0;  /* Level of refinement, h = 2^{-l} */
    2066:   mpfr_t          alpha;             /* Half-width of the integration interval */
    2067:   mpfr_t          beta;              /* Center of the integration interval */
    2068:   mpfr_t          h;                 /* Step size, length between x_k */
    2069:   mpfr_t          osum;              /* Integral on last level */
    2070:   mpfr_t          psum;              /* Integral on the level before the last level */
    2071:   mpfr_t          sum;               /* Integral on current level */
    2072:   mpfr_t          yk;                /* Quadrature point 1 - x_k on reference domain [-1, 1] */
    2073:   mpfr_t          lx, rx;            /* Quadrature points to the left and right of 0 on the real domain [a, b] */
    2074:   mpfr_t          wk;                /* Quadrature weight at x_k */
    2075:   PetscReal       lval, rval, rtmp;  /* Terms in the quadature sum to the left and right of 0 */
    2076:   PetscInt        d;                 /* Digits of precision in the integral */
    2077:   mpfr_t          pi2, kh, msinh, mcosh, maxTerm, curTerm, tmp;

    2080:   /* Create high precision storage */
    2081:   mpfr_inits2(PetscCeilReal(safetyFactor*digits*PetscLogReal(10.)/PetscLogReal(2.)), alpha, beta, h, sum, osum, psum, yk, wk, lx, rx, tmp, maxTerm, curTerm, pi2, kh, msinh, mcosh, NULL);
    2082:   /* Initialization */
    2083:   mpfr_set_d(alpha, 0.5*(b-a), MPFR_RNDN);
    2084:   mpfr_set_d(beta,  0.5*(b+a), MPFR_RNDN);
    2085:   mpfr_set_d(osum,  0.0,       MPFR_RNDN);
    2086:   mpfr_set_d(psum,  0.0,       MPFR_RNDN);
    2087:   mpfr_set_d(h,     1.0,       MPFR_RNDN);
    2088:   mpfr_const_pi(pi2, MPFR_RNDN);
    2089:   mpfr_mul_d(pi2, pi2, 0.5, MPFR_RNDN);
    2090:   /* Center term */
    2091:   rtmp = 0.5*(b+a);
    2092:   func(&rtmp, ctx, &lval);
    2093:   mpfr_set(sum, pi2, MPFR_RNDN);
    2094:   mpfr_mul(sum, sum, alpha, MPFR_RNDN);
    2095:   mpfr_mul_d(sum, sum, lval, MPFR_RNDN);
    2096:   /* */
    2097:   do {
    2098:     PetscReal d1, d2, d3, d4;
    2099:     PetscInt  k = 1;

    2101:     ++l;
    2102:     mpfr_set_d(maxTerm, 0.0, MPFR_RNDN);
    2103:     /* PetscPrintf(PETSC_COMM_SELF, "LEVEL %D sum: %15.15f\n", l, sum); */
    2104:     /* At each level of refinement, h --> h/2 and sum --> sum/2 */
    2105:     mpfr_set(psum, osum, MPFR_RNDN);
    2106:     mpfr_set(osum,  sum, MPFR_RNDN);
    2107:     mpfr_mul_d(h,   h,   0.5, MPFR_RNDN);
    2108:     mpfr_mul_d(sum, sum, 0.5, MPFR_RNDN);
    2109:     do {
    2110:       mpfr_set_si(kh, k, MPFR_RNDN);
    2111:       mpfr_mul(kh, kh, h, MPFR_RNDN);
    2112:       /* Weight */
    2113:       mpfr_set(wk, h, MPFR_RNDN);
    2114:       mpfr_sinh_cosh(msinh, mcosh, kh, MPFR_RNDN);
    2115:       mpfr_mul(msinh, msinh, pi2, MPFR_RNDN);
    2116:       mpfr_mul(mcosh, mcosh, pi2, MPFR_RNDN);
    2117:       mpfr_cosh(tmp, msinh, MPFR_RNDN);
    2118:       mpfr_sqr(tmp, tmp, MPFR_RNDN);
    2119:       mpfr_mul(wk, wk, mcosh, MPFR_RNDN);
    2120:       mpfr_div(wk, wk, tmp, MPFR_RNDN);
    2121:       /* Abscissa */
    2122:       mpfr_set_d(yk, 1.0, MPFR_RNDZ);
    2123:       mpfr_cosh(tmp, msinh, MPFR_RNDN);
    2124:       mpfr_div(yk, yk, tmp, MPFR_RNDZ);
    2125:       mpfr_exp(tmp, msinh, MPFR_RNDN);
    2126:       mpfr_div(yk, yk, tmp, MPFR_RNDZ);
    2127:       /* Quadrature points */
    2128:       mpfr_sub_d(lx, yk, 1.0, MPFR_RNDZ);
    2129:       mpfr_mul(lx, lx, alpha, MPFR_RNDU);
    2130:       mpfr_add(lx, lx, beta, MPFR_RNDU);
    2131:       mpfr_d_sub(rx, 1.0, yk, MPFR_RNDZ);
    2132:       mpfr_mul(rx, rx, alpha, MPFR_RNDD);
    2133:       mpfr_add(rx, rx, beta, MPFR_RNDD);
    2134:       /* Evaluation */
    2135:       rtmp = mpfr_get_d(lx, MPFR_RNDU);
    2136:       func(&rtmp, ctx, &lval);
    2137:       rtmp = mpfr_get_d(rx, MPFR_RNDD);
    2138:       func(&rtmp, ctx, &rval);
    2139:       /* Update */
    2140:       mpfr_mul(tmp, wk, alpha, MPFR_RNDN);
    2141:       mpfr_mul_d(tmp, tmp, lval, MPFR_RNDN);
    2142:       mpfr_add(sum, sum, tmp, MPFR_RNDN);
    2143:       mpfr_abs(tmp, tmp, MPFR_RNDN);
    2144:       mpfr_max(maxTerm, maxTerm, tmp, MPFR_RNDN);
    2145:       mpfr_set(curTerm, tmp, MPFR_RNDN);
    2146:       mpfr_mul(tmp, wk, alpha, MPFR_RNDN);
    2147:       mpfr_mul_d(tmp, tmp, rval, MPFR_RNDN);
    2148:       mpfr_add(sum, sum, tmp, MPFR_RNDN);
    2149:       mpfr_abs(tmp, tmp, MPFR_RNDN);
    2150:       mpfr_max(maxTerm, maxTerm, tmp, MPFR_RNDN);
    2151:       mpfr_max(curTerm, curTerm, tmp, MPFR_RNDN);
    2152:       ++k;
    2153:       /* Only need to evaluate every other point on refined levels */
    2154:       if (l != 1) ++k;
    2155:       mpfr_log10(tmp, wk, MPFR_RNDN);
    2156:       mpfr_abs(tmp, tmp, MPFR_RNDN);
    2157:     } while (mpfr_get_d(tmp, MPFR_RNDN) < safetyFactor*digits); /* Only need to evaluate sum until weights are < 32 digits of precision */
    2158:     mpfr_sub(tmp, sum, osum, MPFR_RNDN);
    2159:     mpfr_abs(tmp, tmp, MPFR_RNDN);
    2160:     mpfr_log10(tmp, tmp, MPFR_RNDN);
    2161:     d1 = mpfr_get_d(tmp, MPFR_RNDN);
    2162:     mpfr_sub(tmp, sum, psum, MPFR_RNDN);
    2163:     mpfr_abs(tmp, tmp, MPFR_RNDN);
    2164:     mpfr_log10(tmp, tmp, MPFR_RNDN);
    2165:     d2 = mpfr_get_d(tmp, MPFR_RNDN);
    2166:     mpfr_log10(tmp, maxTerm, MPFR_RNDN);
    2167:     d3 = mpfr_get_d(tmp, MPFR_RNDN) - digits;
    2168:     mpfr_log10(tmp, curTerm, MPFR_RNDN);
    2169:     d4 = mpfr_get_d(tmp, MPFR_RNDN);
    2170:     d  = PetscAbsInt(PetscMin(0, PetscMax(PetscMax(PetscMax(PetscSqr(d1)/d2, 2*d1), d3), d4)));
    2171:   } while (d < digits && l < 8);
    2172:   *sol = mpfr_get_d(sum, MPFR_RNDN);
    2173:   /* Cleanup */
    2174:   mpfr_clears(alpha, beta, h, sum, osum, psum, yk, wk, lx, rx, tmp, maxTerm, curTerm, pi2, kh, msinh, mcosh, NULL);
    2175:   return 0;
    2176: }
    2177: #else

    2179: PetscErrorCode PetscDTTanhSinhIntegrateMPFR(void (*func)(const PetscReal[], void *, PetscReal *), PetscReal a, PetscReal b, PetscInt digits, void *ctx, PetscReal *sol)
    2180: {
    2181:   SETERRQ(PETSC_COMM_SELF, PETSC_ERR_SUP, "This method will not work without MPFR. Reconfigure using --download-mpfr --download-gmp");
    2182: }
    2183: #endif

    2185: /*@
    2186:   PetscDTTensorQuadratureCreate - create the tensor product quadrature from two lower-dimensional quadratures

    2188:   Not Collective

    2190:   Input Parameters:
    2191: + q1 - The first quadrature
    2192: - q2 - The second quadrature

    2194:   Output Parameter:
    2195: . q - A PetscQuadrature object

    2197:   Level: intermediate

    2199: .seealso: PetscDTGaussTensorQuadrature()
    2200: @*/
    2201: PetscErrorCode PetscDTTensorQuadratureCreate(PetscQuadrature q1, PetscQuadrature q2, PetscQuadrature *q)
    2202: {
    2203:   const PetscReal *x1, *w1, *x2, *w2;
    2204:   PetscReal       *x, *w;
    2205:   PetscInt         dim1, Nc1, Np1, order1, qa, d1;
    2206:   PetscInt         dim2, Nc2, Np2, order2, qb, d2;
    2207:   PetscInt         dim,  Nc,  Np,  order, qc, d;

    2212:   PetscQuadratureGetOrder(q1, &order1);
    2213:   PetscQuadratureGetOrder(q2, &order2);
    2215:   PetscQuadratureGetData(q1, &dim1, &Nc1, &Np1, &x1, &w1);
    2216:   PetscQuadratureGetData(q2, &dim2, &Nc2, &Np2, &x2, &w2);

    2219:   dim   = dim1 + dim2;
    2220:   Nc    = Nc1;
    2221:   Np    = Np1 * Np2;
    2222:   order = order1;
    2223:   PetscQuadratureCreate(PETSC_COMM_SELF, q);
    2224:   PetscQuadratureSetOrder(*q, order);
    2225:   PetscMalloc1(Np*dim, &x);
    2226:   PetscMalloc1(Np, &w);
    2227:   for (qa = 0, qc = 0; qa < Np1; ++qa) {
    2228:     for (qb = 0; qb < Np2; ++qb, ++qc) {
    2229:       for (d1 = 0, d = 0; d1 < dim1; ++d1, ++d) {
    2230:         x[qc*dim+d] = x1[qa*dim1+d1];
    2231:       }
    2232:       for (d2 = 0; d2 < dim2; ++d2, ++d) {
    2233:         x[qc*dim+d] = x2[qb*dim2+d2];
    2234:       }
    2235:       w[qc] = w1[qa] * w2[qb];
    2236:     }
    2237:   }
    2238:   PetscQuadratureSetData(*q, dim, Nc, Np, x, w);
    2239:   return 0;
    2240: }

    2242: /* Overwrites A. Can only handle full-rank problems with m>=n
    2243:  * A in column-major format
    2244:  * Ainv in row-major format
    2245:  * tau has length m
    2246:  * worksize must be >= max(1,n)
    2247:  */
    2248: static PetscErrorCode PetscDTPseudoInverseQR(PetscInt m,PetscInt mstride,PetscInt n,PetscReal *A_in,PetscReal *Ainv_out,PetscScalar *tau,PetscInt worksize,PetscScalar *work)
    2249: {
    2250:   PetscBLASInt   M,N,K,lda,ldb,ldwork,info;
    2251:   PetscScalar    *A,*Ainv,*R,*Q,Alpha;

    2253: #if defined(PETSC_USE_COMPLEX)
    2254:   {
    2255:     PetscInt i,j;
    2256:     PetscMalloc2(m*n,&A,m*n,&Ainv);
    2257:     for (j=0; j<n; j++) {
    2258:       for (i=0; i<m; i++) A[i+m*j] = A_in[i+mstride*j];
    2259:     }
    2260:     mstride = m;
    2261:   }
    2262: #else
    2263:   A = A_in;
    2264:   Ainv = Ainv_out;
    2265: #endif

    2267:   PetscBLASIntCast(m,&M);
    2268:   PetscBLASIntCast(n,&N);
    2269:   PetscBLASIntCast(mstride,&lda);
    2270:   PetscBLASIntCast(worksize,&ldwork);
    2271:   PetscFPTrapPush(PETSC_FP_TRAP_OFF);
    2272:   PetscStackCallBLAS("LAPACKgeqrf",LAPACKgeqrf_(&M,&N,A,&lda,tau,work,&ldwork,&info));
    2273:   PetscFPTrapPop();
    2275:   R = A; /* Upper triangular part of A now contains R, the rest contains the elementary reflectors */

    2277:   /* Extract an explicit representation of Q */
    2278:   Q = Ainv;
    2279:   PetscArraycpy(Q,A,mstride*n);
    2280:   K = N;                        /* full rank */
    2281:   PetscStackCallBLAS("LAPACKorgqr",LAPACKorgqr_(&M,&N,&K,Q,&lda,tau,work,&ldwork,&info));

    2284:   /* Compute A^{-T} = (R^{-1} Q^T)^T = Q R^{-T} */
    2285:   Alpha = 1.0;
    2286:   ldb = lda;
    2287:   PetscStackCallBLAS("BLAStrsm",BLAStrsm_("Right","Upper","ConjugateTranspose","NotUnitTriangular",&M,&N,&Alpha,R,&lda,Q,&ldb));
    2288:   /* Ainv is Q, overwritten with inverse */

    2290: #if defined(PETSC_USE_COMPLEX)
    2291:   {
    2292:     PetscInt i;
    2293:     for (i=0; i<m*n; i++) Ainv_out[i] = PetscRealPart(Ainv[i]);
    2294:     PetscFree2(A,Ainv);
    2295:   }
    2296: #endif
    2297:   return 0;
    2298: }

    2300: /* Computes integral of L_p' over intervals {(x0,x1),(x1,x2),...} */
    2301: static PetscErrorCode PetscDTLegendreIntegrate(PetscInt ninterval,const PetscReal *x,PetscInt ndegree,const PetscInt *degrees,PetscBool Transpose,PetscReal *B)
    2302: {
    2303:   PetscReal      *Bv;
    2304:   PetscInt       i,j;

    2306:   PetscMalloc1((ninterval+1)*ndegree,&Bv);
    2307:   /* Point evaluation of L_p on all the source vertices */
    2308:   PetscDTLegendreEval(ninterval+1,x,ndegree,degrees,Bv,NULL,NULL);
    2309:   /* Integral over each interval: \int_a^b L_p' = L_p(b)-L_p(a) */
    2310:   for (i=0; i<ninterval; i++) {
    2311:     for (j=0; j<ndegree; j++) {
    2312:       if (Transpose) B[i+ninterval*j] = Bv[(i+1)*ndegree+j] - Bv[i*ndegree+j];
    2313:       else           B[i*ndegree+j]   = Bv[(i+1)*ndegree+j] - Bv[i*ndegree+j];
    2314:     }
    2315:   }
    2316:   PetscFree(Bv);
    2317:   return 0;
    2318: }

    2320: /*@
    2321:    PetscDTReconstructPoly - create matrix representing polynomial reconstruction using cell intervals and evaluation at target intervals

    2323:    Not Collective

    2325:    Input Parameters:
    2326: +  degree - degree of reconstruction polynomial
    2327: .  nsource - number of source intervals
    2328: .  sourcex - sorted coordinates of source cell boundaries (length nsource+1)
    2329: .  ntarget - number of target intervals
    2330: -  targetx - sorted coordinates of target cell boundaries (length ntarget+1)

    2332:    Output Parameter:
    2333: .  R - reconstruction matrix, utarget = sum_s R[t*nsource+s] * usource[s]

    2335:    Level: advanced

    2337: .seealso: PetscDTLegendreEval()
    2338: @*/
    2339: PetscErrorCode PetscDTReconstructPoly(PetscInt degree,PetscInt nsource,const PetscReal *sourcex,PetscInt ntarget,const PetscReal *targetx,PetscReal *R)
    2340: {
    2341:   PetscInt       i,j,k,*bdegrees,worksize;
    2342:   PetscReal      xmin,xmax,center,hscale,*sourcey,*targety,*Bsource,*Bsinv,*Btarget;
    2343:   PetscScalar    *tau,*work;

    2349:   if (PetscDefined(USE_DEBUG)) {
    2350:     for (i=0; i<nsource; i++) {
    2352:     }
    2353:     for (i=0; i<ntarget; i++) {
    2355:     }
    2356:   }
    2357:   xmin = PetscMin(sourcex[0],targetx[0]);
    2358:   xmax = PetscMax(sourcex[nsource],targetx[ntarget]);
    2359:   center = (xmin + xmax)/2;
    2360:   hscale = (xmax - xmin)/2;
    2361:   worksize = nsource;
    2362:   PetscMalloc4(degree+1,&bdegrees,nsource+1,&sourcey,nsource*(degree+1),&Bsource,worksize,&work);
    2363:   PetscMalloc4(nsource,&tau,nsource*(degree+1),&Bsinv,ntarget+1,&targety,ntarget*(degree+1),&Btarget);
    2364:   for (i=0; i<=nsource; i++) sourcey[i] = (sourcex[i]-center)/hscale;
    2365:   for (i=0; i<=degree; i++) bdegrees[i] = i+1;
    2366:   PetscDTLegendreIntegrate(nsource,sourcey,degree+1,bdegrees,PETSC_TRUE,Bsource);
    2367:   PetscDTPseudoInverseQR(nsource,nsource,degree+1,Bsource,Bsinv,tau,nsource,work);
    2368:   for (i=0; i<=ntarget; i++) targety[i] = (targetx[i]-center)/hscale;
    2369:   PetscDTLegendreIntegrate(ntarget,targety,degree+1,bdegrees,PETSC_FALSE,Btarget);
    2370:   for (i=0; i<ntarget; i++) {
    2371:     PetscReal rowsum = 0;
    2372:     for (j=0; j<nsource; j++) {
    2373:       PetscReal sum = 0;
    2374:       for (k=0; k<degree+1; k++) {
    2375:         sum += Btarget[i*(degree+1)+k] * Bsinv[k*nsource+j];
    2376:       }
    2377:       R[i*nsource+j] = sum;
    2378:       rowsum += sum;
    2379:     }
    2380:     for (j=0; j<nsource; j++) R[i*nsource+j] /= rowsum; /* normalize each row */
    2381:   }
    2382:   PetscFree4(bdegrees,sourcey,Bsource,work);
    2383:   PetscFree4(tau,Bsinv,targety,Btarget);
    2384:   return 0;
    2385: }

    2387: /*@C
    2388:    PetscGaussLobattoLegendreIntegrate - Compute the L2 integral of a function on the GLL points

    2390:    Not Collective

    2392:    Input Parameters:
    2393: +  n - the number of GLL nodes
    2394: .  nodes - the GLL nodes
    2395: .  weights - the GLL weights
    2396: -  f - the function values at the nodes

    2398:    Output Parameter:
    2399: .  in - the value of the integral

    2401:    Level: beginner

    2403: .seealso: PetscDTGaussLobattoLegendreQuadrature()

    2405: @*/
    2406: PetscErrorCode PetscGaussLobattoLegendreIntegrate(PetscInt n,PetscReal *nodes,PetscReal *weights,const PetscReal *f,PetscReal *in)
    2407: {
    2408:   PetscInt          i;

    2410:   *in = 0.;
    2411:   for (i=0; i<n; i++) {
    2412:     *in += f[i]*f[i]*weights[i];
    2413:   }
    2414:   return 0;
    2415: }

    2417: /*@C
    2418:    PetscGaussLobattoLegendreElementLaplacianCreate - computes the Laplacian for a single 1d GLL element

    2420:    Not Collective

    2422:    Input Parameters:
    2423: +  n - the number of GLL nodes
    2424: .  nodes - the GLL nodes
    2425: -  weights - the GLL weights

    2427:    Output Parameter:
    2428: .  A - the stiffness element

    2430:    Level: beginner

    2432:    Notes:
    2433:     Destroy this with PetscGaussLobattoLegendreElementLaplacianDestroy()

    2435:    You can access entries in this array with AA[i][j] but in memory it is stored in contiguous memory, row oriented (the array is symmetric)

    2437: .seealso: PetscDTGaussLobattoLegendreQuadrature(), PetscGaussLobattoLegendreElementLaplacianDestroy()

    2439: @*/
    2440: PetscErrorCode PetscGaussLobattoLegendreElementLaplacianCreate(PetscInt n,PetscReal *nodes,PetscReal *weights,PetscReal ***AA)
    2441: {
    2442:   PetscReal        **A;
    2443:   const PetscReal  *gllnodes = nodes;
    2444:   const PetscInt   p = n-1;
    2445:   PetscReal        z0,z1,z2 = -1,x,Lpj,Lpr;
    2446:   PetscInt         i,j,nn,r;

    2448:   PetscMalloc1(n,&A);
    2449:   PetscMalloc1(n*n,&A[0]);
    2450:   for (i=1; i<n; i++) A[i] = A[i-1]+n;

    2452:   for (j=1; j<p; j++) {
    2453:     x  = gllnodes[j];
    2454:     z0 = 1.;
    2455:     z1 = x;
    2456:     for (nn=1; nn<p; nn++) {
    2457:       z2 = x*z1*(2.*((PetscReal)nn)+1.)/(((PetscReal)nn)+1.)-z0*(((PetscReal)nn)/(((PetscReal)nn)+1.));
    2458:       z0 = z1;
    2459:       z1 = z2;
    2460:     }
    2461:     Lpj=z2;
    2462:     for (r=1; r<p; r++) {
    2463:       if (r == j) {
    2464:         A[j][j]=2./(3.*(1.-gllnodes[j]*gllnodes[j])*Lpj*Lpj);
    2465:       } else {
    2466:         x  = gllnodes[r];
    2467:         z0 = 1.;
    2468:         z1 = x;
    2469:         for (nn=1; nn<p; nn++) {
    2470:           z2 = x*z1*(2.*((PetscReal)nn)+1.)/(((PetscReal)nn)+1.)-z0*(((PetscReal)nn)/(((PetscReal)nn)+1.));
    2471:           z0 = z1;
    2472:           z1 = z2;
    2473:         }
    2474:         Lpr     = z2;
    2475:         A[r][j] = 4./(((PetscReal)p)*(((PetscReal)p)+1.)*Lpj*Lpr*(gllnodes[j]-gllnodes[r])*(gllnodes[j]-gllnodes[r]));
    2476:       }
    2477:     }
    2478:   }
    2479:   for (j=1; j<p+1; j++) {
    2480:     x  = gllnodes[j];
    2481:     z0 = 1.;
    2482:     z1 = x;
    2483:     for (nn=1; nn<p; nn++) {
    2484:       z2 = x*z1*(2.*((PetscReal)nn)+1.)/(((PetscReal)nn)+1.)-z0*(((PetscReal)nn)/(((PetscReal)nn)+1.));
    2485:       z0 = z1;
    2486:       z1 = z2;
    2487:     }
    2488:     Lpj     = z2;
    2489:     A[j][0] = 4.*PetscPowRealInt(-1.,p)/(((PetscReal)p)*(((PetscReal)p)+1.)*Lpj*(1.+gllnodes[j])*(1.+gllnodes[j]));
    2490:     A[0][j] = A[j][0];
    2491:   }
    2492:   for (j=0; j<p; j++) {
    2493:     x  = gllnodes[j];
    2494:     z0 = 1.;
    2495:     z1 = x;
    2496:     for (nn=1; nn<p; nn++) {
    2497:       z2 = x*z1*(2.*((PetscReal)nn)+1.)/(((PetscReal)nn)+1.)-z0*(((PetscReal)nn)/(((PetscReal)nn)+1.));
    2498:       z0 = z1;
    2499:       z1 = z2;
    2500:     }
    2501:     Lpj=z2;

    2503:     A[p][j] = 4./(((PetscReal)p)*(((PetscReal)p)+1.)*Lpj*(1.-gllnodes[j])*(1.-gllnodes[j]));
    2504:     A[j][p] = A[p][j];
    2505:   }
    2506:   A[0][0]=0.5+(((PetscReal)p)*(((PetscReal)p)+1.)-2.)/6.;
    2507:   A[p][p]=A[0][0];
    2508:   *AA = A;
    2509:   return 0;
    2510: }

    2512: /*@C
    2513:    PetscGaussLobattoLegendreElementLaplacianDestroy - frees the Laplacian for a single 1d GLL element

    2515:    Not Collective

    2517:    Input Parameters:
    2518: +  n - the number of GLL nodes
    2519: .  nodes - the GLL nodes
    2520: .  weights - the GLL weightss
    2521: -  A - the stiffness element

    2523:    Level: beginner

    2525: .seealso: PetscDTGaussLobattoLegendreQuadrature(), PetscGaussLobattoLegendreElementLaplacianCreate()

    2527: @*/
    2528: PetscErrorCode PetscGaussLobattoLegendreElementLaplacianDestroy(PetscInt n,PetscReal *nodes,PetscReal *weights,PetscReal ***AA)
    2529: {
    2530:   PetscFree((*AA)[0]);
    2531:   PetscFree(*AA);
    2532:   *AA  = NULL;
    2533:   return 0;
    2534: }

    2536: /*@C
    2537:    PetscGaussLobattoLegendreElementGradientCreate - computes the gradient for a single 1d GLL element

    2539:    Not Collective

    2541:    Input Parameter:
    2542: +  n - the number of GLL nodes
    2543: .  nodes - the GLL nodes
    2544: .  weights - the GLL weights

    2546:    Output Parameters:
    2547: .  AA - the stiffness element
    2548: -  AAT - the transpose of AA (pass in NULL if you do not need this array)

    2550:    Level: beginner

    2552:    Notes:
    2553:     Destroy this with PetscGaussLobattoLegendreElementGradientDestroy()

    2555:    You can access entries in these arrays with AA[i][j] but in memory it is stored in contiguous memory, row oriented

    2557: .seealso: PetscDTGaussLobattoLegendreQuadrature(), PetscGaussLobattoLegendreElementLaplacianDestroy()

    2559: @*/
    2560: PetscErrorCode PetscGaussLobattoLegendreElementGradientCreate(PetscInt n,PetscReal *nodes,PetscReal *weights,PetscReal ***AA,PetscReal ***AAT)
    2561: {
    2562:   PetscReal        **A, **AT = NULL;
    2563:   const PetscReal  *gllnodes = nodes;
    2564:   const PetscInt   p = n-1;
    2565:   PetscReal        Li, Lj,d0;
    2566:   PetscInt         i,j;

    2568:   PetscMalloc1(n,&A);
    2569:   PetscMalloc1(n*n,&A[0]);
    2570:   for (i=1; i<n; i++) A[i] = A[i-1]+n;

    2572:   if (AAT) {
    2573:     PetscMalloc1(n,&AT);
    2574:     PetscMalloc1(n*n,&AT[0]);
    2575:     for (i=1; i<n; i++) AT[i] = AT[i-1]+n;
    2576:   }

    2578:   if (n==1) {A[0][0] = 0.;}
    2579:   d0 = (PetscReal)p*((PetscReal)p+1.)/4.;
    2580:   for  (i=0; i<n; i++) {
    2581:     for  (j=0; j<n; j++) {
    2582:       A[i][j] = 0.;
    2583:       PetscDTComputeJacobi(0., 0., p, gllnodes[i], &Li);
    2584:       PetscDTComputeJacobi(0., 0., p, gllnodes[j], &Lj);
    2585:       if (i!=j)             A[i][j] = Li/(Lj*(gllnodes[i]-gllnodes[j]));
    2586:       if ((j==i) && (i==0)) A[i][j] = -d0;
    2587:       if (j==i && i==p)     A[i][j] = d0;
    2588:       if (AT) AT[j][i] = A[i][j];
    2589:     }
    2590:   }
    2591:   if (AAT) *AAT = AT;
    2592:   *AA  = A;
    2593:   return 0;
    2594: }

    2596: /*@C
    2597:    PetscGaussLobattoLegendreElementGradientDestroy - frees the gradient for a single 1d GLL element obtained with PetscGaussLobattoLegendreElementGradientCreate()

    2599:    Not Collective

    2601:    Input Parameters:
    2602: +  n - the number of GLL nodes
    2603: .  nodes - the GLL nodes
    2604: .  weights - the GLL weights
    2605: .  AA - the stiffness element
    2606: -  AAT - the transpose of the element

    2608:    Level: beginner

    2610: .seealso: PetscDTGaussLobattoLegendreQuadrature(), PetscGaussLobattoLegendreElementLaplacianCreate(), PetscGaussLobattoLegendreElementAdvectionCreate()

    2612: @*/
    2613: PetscErrorCode PetscGaussLobattoLegendreElementGradientDestroy(PetscInt n,PetscReal *nodes,PetscReal *weights,PetscReal ***AA,PetscReal ***AAT)
    2614: {
    2615:   PetscFree((*AA)[0]);
    2616:   PetscFree(*AA);
    2617:   *AA  = NULL;
    2618:   if (*AAT) {
    2619:     PetscFree((*AAT)[0]);
    2620:     PetscFree(*AAT);
    2621:     *AAT  = NULL;
    2622:   }
    2623:   return 0;
    2624: }

    2626: /*@C
    2627:    PetscGaussLobattoLegendreElementAdvectionCreate - computes the advection operator for a single 1d GLL element

    2629:    Not Collective

    2631:    Input Parameters:
    2632: +  n - the number of GLL nodes
    2633: .  nodes - the GLL nodes
    2634: -  weights - the GLL weightss

    2636:    Output Parameter:
    2637: .  AA - the stiffness element

    2639:    Level: beginner

    2641:    Notes:
    2642:     Destroy this with PetscGaussLobattoLegendreElementAdvectionDestroy()

    2644:    This is the same as the Gradient operator multiplied by the diagonal mass matrix

    2646:    You can access entries in this array with AA[i][j] but in memory it is stored in contiguous memory, row oriented

    2648: .seealso: PetscDTGaussLobattoLegendreQuadrature(), PetscGaussLobattoLegendreElementLaplacianCreate(), PetscGaussLobattoLegendreElementAdvectionDestroy()

    2650: @*/
    2651: PetscErrorCode PetscGaussLobattoLegendreElementAdvectionCreate(PetscInt n,PetscReal *nodes,PetscReal *weights,PetscReal ***AA)
    2652: {
    2653:   PetscReal       **D;
    2654:   const PetscReal  *gllweights = weights;
    2655:   const PetscInt   glln = n;
    2656:   PetscInt         i,j;

    2658:   PetscGaussLobattoLegendreElementGradientCreate(n,nodes,weights,&D,NULL);
    2659:   for (i=0; i<glln; i++) {
    2660:     for (j=0; j<glln; j++) {
    2661:       D[i][j] = gllweights[i]*D[i][j];
    2662:     }
    2663:   }
    2664:   *AA = D;
    2665:   return 0;
    2666: }

    2668: /*@C
    2669:    PetscGaussLobattoLegendreElementAdvectionDestroy - frees the advection stiffness for a single 1d GLL element

    2671:    Not Collective

    2673:    Input Parameters:
    2674: +  n - the number of GLL nodes
    2675: .  nodes - the GLL nodes
    2676: .  weights - the GLL weights
    2677: -  A - advection

    2679:    Level: beginner

    2681: .seealso: PetscDTGaussLobattoLegendreQuadrature(), PetscGaussLobattoLegendreElementAdvectionCreate()

    2683: @*/
    2684: PetscErrorCode PetscGaussLobattoLegendreElementAdvectionDestroy(PetscInt n,PetscReal *nodes,PetscReal *weights,PetscReal ***AA)
    2685: {
    2686:   PetscFree((*AA)[0]);
    2687:   PetscFree(*AA);
    2688:   *AA  = NULL;
    2689:   return 0;
    2690: }

    2692: PetscErrorCode PetscGaussLobattoLegendreElementMassCreate(PetscInt n,PetscReal *nodes,PetscReal *weights,PetscReal ***AA)
    2693: {
    2694:   PetscReal        **A;
    2695:   const PetscReal  *gllweights = weights;
    2696:   const PetscInt   glln = n;
    2697:   PetscInt         i,j;

    2699:   PetscMalloc1(glln,&A);
    2700:   PetscMalloc1(glln*glln,&A[0]);
    2701:   for (i=1; i<glln; i++) A[i] = A[i-1]+glln;
    2702:   if (glln==1) {A[0][0] = 0.;}
    2703:   for  (i=0; i<glln; i++) {
    2704:     for  (j=0; j<glln; j++) {
    2705:       A[i][j] = 0.;
    2706:       if (j==i)     A[i][j] = gllweights[i];
    2707:     }
    2708:   }
    2709:   *AA  = A;
    2710:   return 0;
    2711: }

    2713: PetscErrorCode PetscGaussLobattoLegendreElementMassDestroy(PetscInt n,PetscReal *nodes,PetscReal *weights,PetscReal ***AA)
    2714: {
    2715:   PetscFree((*AA)[0]);
    2716:   PetscFree(*AA);
    2717:   *AA  = NULL;
    2718:   return 0;
    2719: }

    2721: /*@
    2722:   PetscDTIndexToBary - convert an index into a barycentric coordinate.

    2724:   Input Parameters:
    2725: + len - the desired length of the barycentric tuple (usually 1 more than the dimension it represents, so a barycentric coordinate in a triangle has length 3)
    2726: . sum - the value that the sum of the barycentric coordinates (which will be non-negative integers) should sum to
    2727: - index - the index to convert: should be >= 0 and < Binomial(len - 1 + sum, sum)

    2729:   Output Parameter:
    2730: . coord - will be filled with the barycentric coordinate

    2732:   Level: beginner

    2734:   Note: the indices map to barycentric coordinates in lexicographic order, where the first index is the
    2735:   least significant and the last index is the most significant.

    2737: .seealso: PetscDTBaryToIndex()
    2738: @*/
    2739: PetscErrorCode PetscDTIndexToBary(PetscInt len, PetscInt sum, PetscInt index, PetscInt coord[])
    2740: {
    2741:   PetscInt c, d, s, total, subtotal, nexttotal;

    2746:   if (!len) {
    2747:     if (!sum && !index) return 0;
    2748:     SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Invalid index or sum for length 0 barycentric coordinate");
    2749:   }
    2750:   for (c = 1, total = 1; c <= len; c++) {
    2751:     /* total is the number of ways to have a tuple of length c with sum */
    2752:     if (index < total) break;
    2753:     total = (total * (sum + c)) / c;
    2754:   }
    2756:   for (d = c; d < len; d++) coord[d] = 0;
    2757:   for (s = 0, subtotal = 1, nexttotal = 1; c > 0;) {
    2758:     /* subtotal is the number of ways to have a tuple of length c with sum s */
    2759:     /* nexttotal is the number of ways to have a tuple of length c-1 with sum s */
    2760:     if ((index + subtotal) >= total) {
    2761:       coord[--c] = sum - s;
    2762:       index -= (total - subtotal);
    2763:       sum = s;
    2764:       total = nexttotal;
    2765:       subtotal = 1;
    2766:       nexttotal = 1;
    2767:       s = 0;
    2768:     } else {
    2769:       subtotal = (subtotal * (c + s)) / (s + 1);
    2770:       nexttotal = (nexttotal * (c - 1 + s)) / (s + 1);
    2771:       s++;
    2772:     }
    2773:   }
    2774:   return 0;
    2775: }

    2777: /*@
    2778:   PetscDTBaryToIndex - convert a barycentric coordinate to an index

    2780:   Input Parameters:
    2781: + len - the desired length of the barycentric tuple (usually 1 more than the dimension it represents, so a barycentric coordinate in a triangle has length 3)
    2782: . sum - the value that the sum of the barycentric coordinates (which will be non-negative integers) should sum to
    2783: - coord - a barycentric coordinate with the given length and sum

    2785:   Output Parameter:
    2786: . index - the unique index for the coordinate, >= 0 and < Binomial(len - 1 + sum, sum)

    2788:   Level: beginner

    2790:   Note: the indices map to barycentric coordinates in lexicographic order, where the first index is the
    2791:   least significant and the last index is the most significant.

    2793: .seealso: PetscDTIndexToBary
    2794: @*/
    2795: PetscErrorCode PetscDTBaryToIndex(PetscInt len, PetscInt sum, const PetscInt coord[], PetscInt *index)
    2796: {
    2797:   PetscInt c;
    2798:   PetscInt i;
    2799:   PetscInt total;

    2803:   if (!len) {
    2804:     if (!sum) {
    2805:       *index = 0;
    2806:       return 0;
    2807:     }
    2808:     SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Invalid index or sum for length 0 barycentric coordinate");
    2809:   }
    2810:   for (c = 1, total = 1; c < len; c++) total = (total * (sum + c)) / c;
    2811:   i = total - 1;
    2812:   c = len - 1;
    2813:   sum -= coord[c];
    2814:   while (sum > 0) {
    2815:     PetscInt subtotal;
    2816:     PetscInt s;

    2818:     for (s = 1, subtotal = 1; s < sum; s++) subtotal = (subtotal * (c + s)) / s;
    2819:     i   -= subtotal;
    2820:     sum -= coord[--c];
    2821:   }
    2822:   *index = i;
    2823:   return 0;
    2824: }