Date: 2024-09-25T09:33:27+00:00

Actual source code: test8.c
slepc-3.21.2 2024-09-25
Report Typos and Errors

      1: /*
      2:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      3:    SLEPc - Scalable Library for Eigenvalue Problem Computations
      4:    Copyright (c) 2002-, Universitat Politecnica de Valencia, Spain

      6:    This file is part of SLEPc.
      7:    SLEPc is distributed under a 2-clause BSD license (see LICENSE).
      8:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      9: */

     11: static char help[] = "Solves the same eigenproblem as in example ex2, but using a shell matrix. "
     12:   "The problem is a standard symmetric eigenproblem corresponding to the 2-D Laplacian operator.\n\n"
     13:   "The command line options are:\n"
     14:   "  -n <n>, where <n> = number of grid subdivisions in both x and y dimensions.\n\n";

     16: #include <slepceps.h>
     17: #include <petscblaslapack.h>

     19: /*
     20:    User-defined routines
     21: */
     22: PetscErrorCode MatMult_Laplacian2D(Mat A,Vec x,Vec y);
     23: PetscErrorCode MatGetDiagonal_Laplacian2D(Mat A,Vec diag);

     25: int main(int argc,char **argv)
     26: {
     27:   Mat            A;               /* operator matrix */
     28:   EPS            eps;             /* eigenproblem solver context */
     29:   PetscReal      tol=1000*PETSC_MACHINE_EPSILON;
     30:   PetscMPIInt    size;
     31:   PetscInt       N,n=10,nev;

     33:   PetscFunctionBeginUser;
     34:   PetscCall(SlepcInitialize(&argc,&argv,(char*)0,help));
     35:   PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD,&size));
     36:   PetscCheck(size==1,PETSC_COMM_WORLD,PETSC_ERR_WRONG_MPI_SIZE,"This is a uniprocessor example only");

     38:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL));
     39:   N = n*n;
     40:   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"\n2-D Laplacian Eigenproblem (matrix-free version), N=%" PetscInt_FMT " (%" PetscInt_FMT "x%" PetscInt_FMT " grid)\n\n",N,n,n));

     42:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     43:      Compute the operator matrix that defines the eigensystem, Ax=kx
     44:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     46:   PetscCall(MatCreateShell(PETSC_COMM_WORLD,N,N,N,N,&n,&A));
     47:   PetscCall(MatShellSetOperation(A,MATOP_MULT,(void(*)(void))MatMult_Laplacian2D));
     48:   PetscCall(MatShellSetOperation(A,MATOP_MULT_TRANSPOSE,(void(*)(void))MatMult_Laplacian2D));
     49:   PetscCall(MatShellSetOperation(A,MATOP_GET_DIAGONAL,(void(*)(void))MatGetDiagonal_Laplacian2D));

     51:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     52:                 Create the eigensolver and set various options
     53:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     55:   /*
     56:      Create eigensolver context
     57:   */
     58:   PetscCall(EPSCreate(PETSC_COMM_WORLD,&eps));

     60:   /*
     61:      Set operators. In this case, it is a standard eigenvalue problem
     62:   */
     63:   PetscCall(EPSSetOperators(eps,A,NULL));
     64:   PetscCall(EPSSetProblemType(eps,EPS_HEP));
     65:   PetscCall(EPSSetTolerances(eps,tol,PETSC_DEFAULT));

     67:   /*
     68:      Set solver parameters at runtime
     69:   */
     70:   PetscCall(EPSSetFromOptions(eps));

     72:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     73:                       Solve the eigensystem
     74:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     76:   PetscCall(EPSSolve(eps));
     77:   PetscCall(EPSGetDimensions(eps,&nev,NULL,NULL));
     78:   PetscCall(PetscPrintf(PETSC_COMM_WORLD," Number of requested eigenvalues: %" PetscInt_FMT "\n",nev));

     80:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     81:                     Display solution and clean up
     82:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     84:   PetscCall(EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL));
     85:   PetscCall(EPSDestroy(&eps));
     86:   PetscCall(MatDestroy(&A));
     87:   PetscCall(SlepcFinalize());
     88:   return 0;
     89: }

     91: /*
     92:     Compute the matrix vector multiplication y<---T*x where T is a nx by nx
     93:     tridiagonal matrix with DD on the diagonal, DL on the subdiagonal, and
     94:     DU on the superdiagonal.
     95:  */
     96: static void tv(int nx,const PetscScalar *x,PetscScalar *y)
     97: {
     98:   PetscScalar dd,dl,du;
     99:   int         j;

    101:   dd  = 4.0;
    102:   dl  = -1.0;
    103:   du  = -1.0;

    105:   y[0] =  dd*x[0] + du*x[1];
    106:   for (j=1;j<nx-1;j++)
    107:     y[j] = dl*x[j-1] + dd*x[j] + du*x[j+1];
    108:   y[nx-1] = dl*x[nx-2] + dd*x[nx-1];
    109: }

    111: /*
    112:     Matrix-vector product subroutine for the 2D Laplacian.

    114:     The matrix used is the 2 dimensional discrete Laplacian on unit square with
    115:     zero Dirichlet boundary condition.

    117:     Computes y <-- A*x, where A is the block tridiagonal matrix

    119:                  | T -I          |
    120:                  |-I  T -I       |
    121:              A = |   -I  T       |
    122:                  |        ...  -I|
    123:                  |           -I T|

    125:     The subroutine TV is called to compute y<--T*x.
    126:  */
    127: PetscErrorCode MatMult_Laplacian2D(Mat A,Vec x,Vec y)
    128: {
    129:   void              *ctx;
    130:   int               nx,lo,i,j;
    131:   const PetscScalar *px;
    132:   PetscScalar       *py;

    134:   PetscFunctionBeginUser;
    135:   PetscCall(MatShellGetContext(A,&ctx));
    136:   nx = *(int*)ctx;
    137:   PetscCall(VecGetArrayRead(x,&px));
    138:   PetscCall(VecGetArray(y,&py));

    140:   tv(nx,&px[0],&py[0]);
    141:   for (i=0;i<nx;i++) py[i] -= px[nx+i];

    143:   for (j=2;j<nx;j++) {
    144:     lo = (j-1)*nx;
    145:     tv(nx,&px[lo],&py[lo]);
    146:     for (i=0;i<nx;i++) py[lo+i] -= px[lo-nx+i] + px[lo+nx+i];
    147:   }

    149:   lo = (nx-1)*nx;
    150:   tv(nx,&px[lo],&py[lo]);
    151:   for (i=0;i<nx;i++) py[lo+i] -= px[lo-nx+i];

    153:   PetscCall(VecRestoreArrayRead(x,&px));
    154:   PetscCall(VecRestoreArray(y,&py));
    155:   PetscFunctionReturn(PETSC_SUCCESS);
    156: }

    158: PetscErrorCode MatGetDiagonal_Laplacian2D(Mat A,Vec diag)
    159: {
    160:   PetscFunctionBeginUser;
    161:   PetscCall(VecSet(diag,4.0));
    162:   PetscFunctionReturn(PETSC_SUCCESS);
    163: }

    165: /*TEST

    167:    testset:
    168:       args: -n 20 -eps_nev 4 -eps_ncv 11 -eps_max_it 40000
    169:       requires: !single
    170:       output_file: output/test8_1.out
    171:       test:
    172:          suffix: 1
    173:          args: -eps_type {{power subspace arnoldi}}
    174:       test:
    175:          suffix: 1_lanczos
    176:          args: -eps_type lanczos -eps_lanczos_reorthog local
    177:       test:
    178:          suffix: 1_lapack
    179:          args: -eps_type lapack
    180:          timeoutfactor: 2
    181:       test:
    182:          suffix: 1_elemental
    183:          args: -eps_type elemental
    184:          requires: elemental
    185:       test:
    186:          suffix: 1_krylovschur_vecs
    187:          args: -bv_type vecs -bv_orthog_refine always -eps_ncv 10 -vec_mdot_use_gemv 0
    188:       test:
    189:          suffix: 1_jd
    190:          args: -eps_type jd -eps_jd_blocksize 3
    191:       test:
    192:          suffix: 1_gd
    193:          args: -eps_type gd -eps_gd_blocksize 3 -eps_tol 1e-8
    194:       test:
    195:          suffix: 1_gd2
    196:          args: -eps_type gd -eps_gd_double_expansion
    197:       test:
    198:          suffix: 1_primme
    199:          args: -eps_type primme -eps_conv_abs -eps_largest_magnitude
    200:          requires: primme

    202:    testset:
    203:       args: -eps_nev 4 -eps_smallest_real -eps_max_it 600
    204:       output_file: output/test8_2.out
    205:       test:
    206:          suffix: 2
    207:          args: -eps_type {{rqcg lobpcg}}
    208:       test:
    209:          suffix: 2_lanczos
    210:          args: -eps_type lanczos -eps_lanczos_reorthog local
    211:       test:
    212:          suffix: 2_arpack
    213:          args: -eps_type arpack -eps_ncv 6
    214:          requires: arpack !single
    215:       test:
    216:          suffix: 2_primme
    217:          args: -eps_type primme -eps_conv_abs -eps_primme_method lobpcg_orthobasisw -eps_ncv 24
    218:          requires: primme

    220:    testset:
    221:       args: -eps_nev 12 -eps_mpd 9 -eps_smallest_real -eps_max_it 1000
    222:       output_file: output/test8_3.out
    223:       test:
    224:          suffix: 3_rqcg
    225:          args: -eps_type rqcg
    226:       test:
    227:          suffix: 3_lanczos
    228:          args: -eps_type lanczos -eps_lanczos_reorthog local
    229:       test:
    230:          suffix: 3_lobpcg
    231:          args: -eps_type lobpcg -eps_lobpcg_blocksize 3 -eps_lobpcg_locking 0 -st_ksp_type preonly -st_pc_type jacobi
    232:          requires: !__float128
    233:       test:
    234:          suffix: 3_lobpcg_quad
    235:          args: -eps_type lobpcg -eps_lobpcg_blocksize 3 -eps_lobpcg_locking 0 -st_ksp_type preonly -st_pc_type jacobi -eps_tol 1e-25
    236:          requires: __float128
    237: TEST*/