Date: 2021-09-20T09:44:02+00:00

Actual source code: test12.c
slepc-3.15.2 2021-09-20
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      1: /*
      2:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      3:    SLEPc - Scalable Library for Eigenvalue Problem Computations
      4:    Copyright (c) 2002-2021, 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: {
     39:   PetscLogDouble now,deadline = *(PetscLogDouble*)ctx;

     42:   /* check if usual termination conditions are met */
     43:   SVDStoppingBasic(svd,its,max_it,nconv,nev,reason,NULL);
     44:   if (*reason==SVD_CONVERGED_ITERATING) {
     45:     /* check if deadline has expired */
     46:     PetscTime(&now);
     47:     if (now>deadline) *reason = SVD_CONVERGED_USER;
     48:   }
     49:   return(0);
     50: }

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

     65:   SlepcInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;

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

     75:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     76:         Generate the matrix
     77:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     79:   MatCreate(PETSC_COMM_WORLD,&A);
     80:   MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,m,n);
     81:   MatSetFromOptions(A);
     82:   MatSetUp(A);
     83:   MatGetOwnershipRange(A,&Istart,&Iend);
     84:   for (i=Istart;i<Iend;i++) {
     85:     col[0]=i; col[1]=i+1;
     86:     if (i<n-1) {
     87:       MatSetValues(A,1,&i,2,col,value,INSERT_VALUES);
     88:     } else if (i==n-1) {
     89:       MatSetValue(A,i,col[0],value[0],INSERT_VALUES);
     90:     }
     91:   }
     92:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
     93:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);

     95:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     96:         Compute singular values
     97:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     99:   SVDCreate(PETSC_COMM_WORLD,&svd);
    100:   SVDSetOperators(svd,A,NULL);
    101:   SVDSetWhichSingularTriplets(svd,SVD_SMALLEST);
    102:   SVDSetTolerances(svd,PETSC_DEFAULT,1000);
    103:   SVDSetType(svd,SVDTRLANCZOS);
    104:   SVDSetStoppingTestFunction(svd,MyStoppingTest,&deadline,NULL);
    105:   SVDSetFromOptions(svd);

    107:   /* call the solver */
    108:   SVDSolve(svd);

    110:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    111:                     Display solution and clean up
    112:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    114:   /* show detailed info unless -terse option is given by user */
    115:   PetscOptionsHasName(NULL,NULL,"-terse",&terse);
    116:   if (terse) {
    117:     SVDErrorView(svd,SVD_ERROR_RELATIVE,PETSC_VIEWER_STDOUT_WORLD);
    118:   } else {
    119:     PetscViewerASCIIGetStdout(PETSC_COMM_WORLD,&viewer);
    120:     PetscViewerPushFormat(viewer,PETSC_VIEWER_ASCII_INFO_DETAIL);
    121:     SVDGetConvergedReason(svd,&reason);
    122:     if (reason!=SVD_CONVERGED_USER) {
    123:       SVDConvergedReasonView(svd,viewer);
    124:       SVDErrorView(svd,SVD_ERROR_RELATIVE,viewer);
    125:     } else {
    126:       SVDGetConverged(svd,&nconv);
    127:       PetscViewerASCIIPrintf(viewer,"SVD solve finished with %D converged eigenpairs; reason=%s\n",nconv,SVDConvergedReasons[reason]);
    128:     }
    129:     PetscViewerPopFormat(viewer);
    130:   }
    131:   SVDDestroy(&svd);
    132:   MatDestroy(&A);
    133:   SlepcFinalize();
    134:   return ierr;
    135: }

    137: /*TEST

    139:    test:
    140:       suffix: 1
    141:       args: -m 750 -seconds 0.1 -svd_max_it 10000

    143: TEST*/