Date: 2022-11-02T11:47:14+00:00

Actual source code: test12.c
slepc-3.18.1 2022-11-02
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[] = "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;

     41:   /* check if usual termination conditions are met */
     42:   SVDStoppingBasic(svd,its,max_it,nconv,nev,reason,NULL);
     43:   if (*reason==SVD_CONVERGED_ITERATING) {
     44:     /* check if deadline has expired */
     45:     PetscTime(&now);
     46:     if (now>deadline) *reason = SVD_CONVERGED_USER;
     47:   }
     48:   return 0;
     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;

     64:   SlepcInitialize(&argc,&argv,(char*)0,help);

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

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

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

     91:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     92:         Compute singular values
     93:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

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

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

    106:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    107:                     Display solution and clean up
    108:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    110:   /* show detailed info unless -terse option is given by user */
    111:   PetscOptionsHasName(NULL,NULL,"-terse",&terse);
    112:   if (terse) SVDErrorView(svd,SVD_ERROR_RELATIVE,PETSC_VIEWER_STDOUT_WORLD);
    113:   else {
    114:     PetscViewerASCIIGetStdout(PETSC_COMM_WORLD,&viewer);
    115:     PetscViewerPushFormat(viewer,PETSC_VIEWER_ASCII_INFO_DETAIL);
    116:     SVDGetConvergedReason(svd,&reason);
    117:     if (reason!=SVD_CONVERGED_USER) {
    118:       SVDConvergedReasonView(svd,viewer);
    119:       SVDErrorView(svd,SVD_ERROR_RELATIVE,viewer);
    120:     } else {
    121:       SVDGetConverged(svd,&nconv);
    122:       PetscViewerASCIIPrintf(viewer,"SVD solve finished with %" PetscInt_FMT " converged eigenpairs; reason=%s\n",nconv,SVDConvergedReasons[reason]);
    123:     }
    124:     PetscViewerPopFormat(viewer);
    125:   }
    126:   SVDDestroy(&svd);
    127:   MatDestroy(&A);
    128:   SlepcFinalize();
    129:   return 0;
    130: }

    132: /*TEST

    134:    test:
    135:       suffix: 1
    136:       args: -m 750 -seconds 0.1 -svd_max_it 10000

    138: TEST*/