Date: 2022-08-02T03:14:46+00:00

Actual source code: ex10.c

      2: static char help[] = "Solve a small system and a large system through preloading\n\
      3:   Input arguments are:\n\
      4:   -permute <natural,rcm,nd,...> : solve system in permuted indexing\n\
      5:   -f0 <small_sys_binary> -f1 <large_sys_binary> \n\n";

      7: /*
      8:   Include "petscksp.h" so that we can use KSP solvers.  Note that this file
      9:   automatically includes:
     10:      petscsys.h       - base PETSc routines   petscvec.h - vectors
     11:      petscmat.h - matrices
     12:      petscis.h     - index sets            petscksp.h - Krylov subspace methods
     13:      petscviewer.h - viewers               petscpc.h  - preconditioners
     14: */
     15: #include <petscksp.h>

     17: typedef enum {
     18:   RHS_FILE,
     19:   RHS_ONE,
     20:   RHS_RANDOM
     21: } RHSType;
     22: const char *const RHSTypes[] = {"FILE", "ONE", "RANDOM", "RHSType", "RHS_", NULL};

     24: PetscErrorCode CheckResult(KSP *ksp, Mat *A, Vec *b, Vec *x, IS *rowperm)
     25: {
     26:   PetscReal         norm;        /* norm of solution error */
     27:   PetscInt          its;
     28:   KSPGetTotalIterations(*ksp,&its);
     29:   PetscPrintf(PETSC_COMM_WORLD,"Number of iterations = %d\n",its);

     31:   KSPGetResidualNorm(*ksp,&norm);
     32:   if (norm < 1.e-12) {
     33:     PetscPrintf(PETSC_COMM_WORLD,"Residual norm < 1.e-12\n");
     34:   } else {
     35:     PetscPrintf(PETSC_COMM_WORLD,"Residual norm %e\n",(double)norm);
     36:   }

     38:   KSPDestroy(ksp);
     39:   MatDestroy(A);
     40:   VecDestroy(x);
     41:   VecDestroy(b);
     42:   ISDestroy(rowperm);
     43:   return 0;
     44: }

     46: PetscErrorCode CreateSystem(const char filename[PETSC_MAX_PATH_LEN], RHSType rhstype, MatOrderingType ordering, PetscBool permute, IS *rowperm_out, Mat *A_out, Vec *b_out, Vec *x_out)
     47: {

     49:   Vec               x,b,b2;
     50:   Mat               A;           /* linear system matrix */
     51:   PetscViewer       viewer;      /* viewer */
     52:   PetscBool         same;
     53:   PetscInt          j,len,start,idx,n1,n2;
     54:   const PetscScalar *val;
     55:   IS                rowperm=NULL,colperm=NULL;

     57:   /* open binary file. Note that we use FILE_MODE_READ to indicate reading from this file */
     58:   PetscViewerBinaryOpen(PETSC_COMM_WORLD,filename,FILE_MODE_READ,&viewer);

     60:   /* load the matrix and vector; then destroy the viewer */
     61:   MatCreate(PETSC_COMM_WORLD,&A);
     62:   MatSetFromOptions(A);
     63:   MatLoad(A,viewer);
     64:   switch (rhstype) {
     65:   case RHS_FILE:
     66:     /* Vectors in the file might a different size than the matrix so we need a
     67:      * Vec whose size hasn't been set yet.  It'll get fixed below.  Otherwise we
     68:      * can create the correct size Vec. */
     69:     VecCreate(PETSC_COMM_WORLD,&b);
     70:     VecLoad(b,viewer);
     71:     break;
     72:   case RHS_ONE:
     73:     MatCreateVecs(A,&b,NULL);
     74:     VecSet(b,1.0);
     75:     break;
     76:   case RHS_RANDOM:
     77:     MatCreateVecs(A,&b,NULL);
     78:     VecSetRandom(b,NULL);
     79:     break;
     80:   }
     81:   PetscViewerDestroy(&viewer);

     83:   /* if the loaded matrix is larger than the vector (due to being padded
     84:      to match the block size of the system), then create a new padded vector
     85:    */
     86:   MatGetLocalSize(A,NULL,&n1);
     87:   VecGetLocalSize(b,&n2);
     88:   same = (n1 == n2)? PETSC_TRUE : PETSC_FALSE;
     89:   MPIU_Allreduce(MPI_IN_PLACE,&same,1,MPIU_BOOL,MPI_LAND,PETSC_COMM_WORLD);

     91:   if (!same) { /* create a new vector b by padding the old one */
     92:     VecCreate(PETSC_COMM_WORLD,&b2);
     93:     VecSetSizes(b2,n1,PETSC_DECIDE);
     94:     VecSetFromOptions(b2);
     95:     VecGetOwnershipRange(b,&start,NULL);
     96:     VecGetLocalSize(b,&len);
     97:     VecGetArrayRead(b,&val);
     98:     for (j=0; j<len; j++) {
     99:       idx = start+j;
    100:       VecSetValues(b2,1,&idx,val+j,INSERT_VALUES);
    101:     }
    102:     VecRestoreArrayRead(b,&val);
    103:     VecDestroy(&b);
    104:     VecAssemblyBegin(b2);
    105:     VecAssemblyEnd(b2);
    106:     b    = b2;
    107:   }
    108:   VecDuplicate(b,&x);

    110:   if (permute) {
    111:     Mat Aperm;
    112:     MatGetOrdering(A,ordering,&rowperm,&colperm);
    113:     MatPermute(A,rowperm,colperm,&Aperm);
    114:     VecPermute(b,colperm,PETSC_FALSE);
    115:     MatDestroy(&A);
    116:     A    = Aperm;               /* Replace original operator with permuted version */
    117:     ISDestroy(&colperm);
    118:   }

    120:   *b_out = b;
    121:   *x_out = x;
    122:   *A_out = A;
    123:   *rowperm_out = rowperm;

    125:   return 0;
    126: }

    128: /* ATTENTION: this is the example used in the Profiling chaper of the PETSc manual,
    129:    where we referenced its profiling stages, preloading and output etc.
    130:    When you modify it, please make sure it is still consistent with the manual.
    131:  */
    132: int main(int argc,char **args)
    133: {
    134:   PetscErrorCode    ierr;
    135:   Vec               x,b;
    136:   Mat               A;           /* linear system matrix */
    137:   KSP               ksp;         /* Krylov subspace method context */
    138:   char              file[2][PETSC_MAX_PATH_LEN],ordering[256]=MATORDERINGRCM;
    139:   RHSType           rhstype = RHS_FILE;
    140:   PetscBool         flg,preload=PETSC_FALSE,trans=PETSC_FALSE,permute=PETSC_FALSE;
    141:   IS                rowperm=NULL;

    143:   PetscInitialize(&argc,&args,(char*)0,help);

    145:   PetscOptionsBegin(PETSC_COMM_WORLD,NULL,"Preloading example options","");
    146:   {
    147:     /*
    148:        Determine files from which we read the two linear systems
    149:        (matrix and right-hand-side vector).
    150:     */
    151:     PetscOptionsBool("-trans","Solve transpose system instead","",trans,&trans,&flg);
    152:     PetscOptionsString("-f","First file to load (small system)","",file[0],file[0],sizeof(file[0]),&flg);
    153:     PetscOptionsFList("-permute","Permute matrix and vector to solve in new ordering","",MatOrderingList,ordering,ordering,sizeof(ordering),&permute);

    155:     if (flg) {
    156:       PetscStrcpy(file[1],file[0]);
    157:       preload = PETSC_FALSE;
    158:     } else {
    159:       PetscOptionsString("-f0","First file to load (small system)","",file[0],file[0],sizeof(file[0]),&flg);
    161:       PetscOptionsString("-f1","Second file to load (larger system)","",file[1],file[1],sizeof(file[1]),&flg);
    162:       if (!flg) preload = PETSC_FALSE;   /* don't bother with second system */
    163:     }

    165:     PetscOptionsEnum("-rhs","Right hand side","",RHSTypes,(PetscEnum)rhstype,(PetscEnum*)&rhstype,NULL);
    166:   }
    167:   PetscOptionsEnd();

    169:   /*
    170:     To use preloading, one usually has code like the following:

    172:     PetscPreLoadBegin(preload,"first stage);
    173:       lines of code
    174:     PetscPreLoadStage("second stage");
    175:       lines of code
    176:     PetscPreLoadEnd();

    178:     The two macro PetscPreLoadBegin() and PetscPreLoadEnd() implicitly form a
    179:     loop with maximal two iterations, depending whether preloading is turned on or
    180:     not. If it is, either through the preload arg of PetscPreLoadBegin or through
    181:     -preload command line, the trip count is 2, otherwise it is 1. One can use the
    182:     predefined variable PetscPreLoadIt within the loop body to get the current
    183:     iteration number, which is 0 or 1. If preload is turned on, the runtime doesn't
    184:     do profiling for the first iteration, but it will do profiling for the second
    185:     iteration instead.

    187:     One can solve a small system in the first iteration and a large system in
    188:     the second iteration. This process preloads the instructions with the small
    189:     system so that more accurate performance monitoring (via -log_view) can be done
    190:     with the large one (that actually is the system of interest).

    192:     But in this example, we turned off preloading and duplicated the code for
    193:     the large system. In general, it is a bad practice and one should not duplicate
    194:     code. We do that because we want to show profiling stages for both the small
    195:     system and the large system.
    196:   */

    198:   /*=========================
    199:       solve a small system
    200:     =========================*/

    202:   PetscPreLoadBegin(preload,"Load System 0");
    203:   CreateSystem(file[0],rhstype,ordering,permute,&rowperm,&A,&b,&x);

    205:   PetscPreLoadStage("KSPSetUp 0");
    206:   KSPCreate(PETSC_COMM_WORLD,&ksp);
    207:   KSPSetOperators(ksp,A,A);
    208:   KSPSetFromOptions(ksp);

    210:   /*
    211:     Here we explicitly call KSPSetUp() and KSPSetUpOnBlocks() to
    212:     enable more precise profiling of setting up the preconditioner.
    213:     These calls are optional, since both will be called within
    214:     KSPSolve() if they haven't been called already.
    215:   */
    216:   KSPSetUp(ksp);
    217:   KSPSetUpOnBlocks(ksp);

    219:   PetscPreLoadStage("KSPSolve 0");
    220:   if (trans) KSPSolveTranspose(ksp,b,x);
    221:   else       KSPSolve(ksp,b,x);

    223:   if (permute) VecPermute(x,rowperm,PETSC_TRUE);

    225:   CheckResult(&ksp,&A,&b,&x,&rowperm);

    227:   /*=========================
    228:     solve a large system
    229:     =========================*/

    231:   PetscPreLoadStage("Load System 1");

    233:   CreateSystem(file[1],rhstype,ordering,permute,&rowperm,&A,&b,&x);

    235:   PetscPreLoadStage("KSPSetUp 1");
    236:   KSPCreate(PETSC_COMM_WORLD,&ksp);
    237:   KSPSetOperators(ksp,A,A);
    238:   KSPSetFromOptions(ksp);

    240:   /*
    241:     Here we explicitly call KSPSetUp() and KSPSetUpOnBlocks() to
    242:     enable more precise profiling of setting up the preconditioner.
    243:     These calls are optional, since both will be called within
    244:     KSPSolve() if they haven't been called already.
    245:   */
    246:   KSPSetUp(ksp);
    247:   KSPSetUpOnBlocks(ksp);

    249:   PetscPreLoadStage("KSPSolve 1");
    250:   if (trans) KSPSolveTranspose(ksp,b,x);
    251:   else       KSPSolve(ksp,b,x);

    253:   if (permute) VecPermute(x,rowperm,PETSC_TRUE);

    255:   CheckResult(&ksp,&A,&b,&x,&rowperm);

    257:   PetscPreLoadEnd();
    258:   /*
    259:      Always call PetscFinalize() before exiting a program.  This routine
    260:        - finalizes the PETSc libraries as well as MPI
    261:        - provides summary and diagnostic information if certain runtime
    262:          options are chosen (e.g., -log_view).
    263:   */
    264:   PetscFinalize();
    265:   return 0;
    266: }

    268: /*TEST

    270:    test:
    271:       TODO: Matrix row/column sizes are not compatible with block size
    272:       suffix: 1
    273:       nsize: 4
    274:       output_file: output/ex10_1.out
    275:       requires: datafilespath double !complex !defined(PETSC_USE_64BIT_INDICES)
    276:       args: -f0 ${DATAFILESPATH}/matrices/medium -f1 ${DATAFILESPATH}/matrices/arco6 -ksp_gmres_classicalgramschmidt -mat_type baij -matload_block_size 3 -pc_type bjacobi

    278:    test:
    279:       TODO: Matrix row/column sizes are not compatible with block size
    280:       suffix: 2
    281:       nsize: 4
    282:       output_file: output/ex10_2.out
    283:       requires: datafilespath double !complex !defined(PETSC_USE_64BIT_INDICES)
    284:       args: -f0 ${DATAFILESPATH}/matrices/medium -f1 ${DATAFILESPATH}/matrices/arco6 -ksp_gmres_classicalgramschmidt -mat_type baij -matload_block_size 3 -pc_type bjacobi -trans

    286:    test:
    287:       suffix: 3
    288:       requires: double complex !defined(PETSC_USE_64BIT_INDICES)
    289:       args: -f ${wPETSC_DIR}/share/petsc/datafiles/matrices/nh-complex-int32-float64 -ksp_type bicg

    291:    test:
    292:       suffix: 4
    293:       args: -f ${DATAFILESPATH}/matrices/medium -ksp_type bicg -permute rcm
    294:       requires: datafilespath double !complex !defined(PETSC_USE_64BIT_INDICES)

    296: TEST*/