Date: 2026-05-01T10:02:10+00:00

Actual source code: test12.c

      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[] = "SVD problem with user-defined stopping test.\n\n"
     12:   "The command line options are:\n"
     13:   "  -m <m>, where <m> = matrix rows.\n"
     14:   "  -n <n>, where <n> = matrix columns (defaults to m+2).\n\n";

     16: #include <slepcsvd.h>
     17: #include <petsctime.h>

     19: /*
     20:    This example computes the singular values of a rectangular bidiagonal matrix

     22:               |  1  2                     |
     23:               |     1  2                  |
     24:               |        1  2               |
     25:           A = |          .  .             |
     26:               |             .  .          |
     27:               |                1  2       |
     28:               |                   1  2    |
     29:  */

     31: /*
     32:     Function for user-defined stopping test.

     34:     Checks that the computing time has not exceeded the deadline.
     35: */
     36: PetscErrorCode MyStoppingTest(SVD svd,PetscInt its,PetscInt max_it,PetscInt nconv,PetscInt nev,SVDConvergedReason *reason,void *ctx)
     37: {
     38:   PetscLogDouble now,deadline = *(PetscLogDouble*)ctx;

     40:   PetscFunctionBeginUser;
     41:   /* check if usual termination conditions are met */
     42:   PetscCall(SVDStoppingBasic(svd,its,max_it,nconv,nev,reason,NULL));
     43:   if (*reason==SVD_CONVERGED_ITERATING) {
     44:     /* check if deadline has expired */
     45:     PetscCall(PetscTime(&now));
     46:     if (now>deadline) *reason = SVD_CONVERGED_USER;
     47:   }
     48:   PetscFunctionReturn(PETSC_SUCCESS);
     49: }

     51: int main(int argc,char **argv)
     52: {
     53:   Mat                A;
     54:   SVD                svd;
     55:   SVDConvergedReason reason;
     56:   PetscInt           m=20,n,Istart,Iend,i,col[2],nconv;
     57:   PetscReal          seconds=2.5;     /* maximum time allowed for computation */
     58:   PetscLogDouble     deadline;        /* time to abort computation */
     59:   PetscScalar        value[] = { 1, 2 };
     60:   PetscBool          terse,flg;
     61:   PetscViewer        viewer;

     63:   PetscFunctionBeginUser;
     64:   PetscCall(SlepcInitialize(&argc,&argv,NULL,help));

     66:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-m",&m,NULL));
     67:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-n",&n,&flg));
     68:   if (!flg) n=m+2;
     69:   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"\nRectangular bidiagonal matrix, m=%" PetscInt_FMT " n=%" PetscInt_FMT "\n\n",m,n));
     70:   PetscCall(PetscOptionsGetReal(NULL,NULL,"-seconds",&seconds,NULL));
     71:   deadline = seconds;
     72:   PetscCall(PetscTimeAdd(&deadline));

     74:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     75:         Generate the matrix
     76:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     78:   PetscCall(MatCreate(PETSC_COMM_WORLD,&A));
     79:   PetscCall(MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,m,n));
     80:   PetscCall(MatSetFromOptions(A));
     81:   PetscCall(MatGetOwnershipRange(A,&Istart,&Iend));
     82:   for (i=Istart;i<Iend;i++) {
     83:     col[0]=i; col[1]=i+1;
     84:     if (i<n-1) PetscCall(MatSetValues(A,1,&i,2,col,value,INSERT_VALUES));
     85:     else if (i==n-1) PetscCall(MatSetValue(A,i,col[0],value[0],INSERT_VALUES));
     86:   }
     87:   PetscCall(MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY));
     88:   PetscCall(MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY));

     90:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     91:         Compute singular values
     92:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     94:   PetscCall(SVDCreate(PETSC_COMM_WORLD,&svd));
     95:   PetscCall(SVDSetOperators(svd,A,NULL));
     96:   PetscCall(SVDSetWhichSingularTriplets(svd,SVD_SMALLEST));
     97:   PetscCall(SVDSetTolerances(svd,PETSC_CURRENT,1000));
     98:   PetscCall(SVDSetType(svd,SVDTRLANCZOS));
     99:   PetscCall(SVDSetStoppingTestFunction(svd,MyStoppingTest,&deadline,NULL));
    100:   PetscCall(SVDSetFromOptions(svd));

    102:   /* call the solver */
    103:   PetscCall(SVDSolve(svd));

    105:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    106:                     Display solution and clean up
    107:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    109:   /* show detailed info unless -terse option is given by user */
    110:   PetscCall(PetscOptionsHasName(NULL,NULL,"-terse",&terse));
    111:   if (terse) PetscCall(SVDErrorView(svd,SVD_ERROR_RELATIVE,PETSC_VIEWER_STDOUT_WORLD));
    112:   else {
    113:     PetscCall(PetscViewerASCIIGetStdout(PETSC_COMM_WORLD,&viewer));
    114:     PetscCall(PetscViewerPushFormat(viewer,PETSC_VIEWER_ASCII_INFO_DETAIL));
    115:     PetscCall(SVDGetConvergedReason(svd,&reason));
    116:     if (reason!=SVD_CONVERGED_USER) {
    117:       PetscCall(SVDConvergedReasonView(svd,viewer));
    118:       PetscCall(SVDErrorView(svd,SVD_ERROR_RELATIVE,viewer));
    119:     } else {
    120:       PetscCall(SVDGetConverged(svd,&nconv));
    121:       PetscCall(PetscViewerASCIIPrintf(viewer,"SVD solve finished with %" PetscInt_FMT " converged eigenpairs; reason=%s\n",nconv,SVDConvergedReasons[reason]));
    122:     }
    123:     PetscCall(PetscViewerPopFormat(viewer));
    124:   }
    125:   PetscCall(SVDDestroy(&svd));
    126:   PetscCall(MatDestroy(&A));
    127:   PetscCall(SlepcFinalize());
    128:   return 0;
    129: }

    131: /*TEST

    133:    test:
    134:       suffix: 1
    135:       args: -m 750 -seconds 0.1 -svd_max_it 10000
    136:       requires: !single

    138: TEST*/