Date: 2021-09-20T09:43:41+00:00

Actual source code: test7.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[] = "Test DSSVD.\n\n";

     13: #include <slepcds.h>

     15: int main(int argc,char **argv)
     16: {
     18:   DS             ds;
     19:   SlepcSC        sc;
     20:   PetscReal      sigma,rnorm,aux;
     21:   PetscScalar    *A,*U,*w;
     22:   PetscInt       i,j,k,n=15,m=10,ld;
     23:   PetscViewer    viewer;
     24:   PetscBool      verbose;

     26:   SlepcInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;
     27:   PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);
     28:   PetscOptionsGetInt(NULL,NULL,"-m",&m,NULL);
     29:   k = PetscMin(n,m);
     30:   PetscPrintf(PETSC_COMM_WORLD,"Solve a Dense System of type SVD - dimension %Dx%D.\n",n,m);
     31:   PetscOptionsHasName(NULL,NULL,"-verbose",&verbose);

     33:   /* Create DS object */
     34:   DSCreate(PETSC_COMM_WORLD,&ds);
     35:   DSSetType(ds,DSSVD);
     36:   DSSetFromOptions(ds);
     37:   ld = n+2;  /* test leading dimension larger than n */
     38:   DSAllocate(ds,ld);
     39:   DSSetDimensions(ds,n,m,0,0);

     41:   /* Set up viewer */
     42:   PetscViewerASCIIGetStdout(PETSC_COMM_WORLD,&viewer);
     43:   PetscViewerPushFormat(viewer,PETSC_VIEWER_ASCII_INFO_DETAIL);
     44:   DSView(ds,viewer);
     45:   PetscViewerPopFormat(viewer);

     47:   /* Fill with a rectangular Toeplitz matrix */
     48:   DSGetArray(ds,DS_MAT_A,&A);
     49:   for (i=0;i<k;i++) A[i+i*ld]=1.0;
     50:   for (j=1;j<3;j++) {
     51:     for (i=0;i<n-j;i++) { if ((i+j)<m) A[i+(i+j)*ld]=(PetscScalar)(j+1); }
     52:   }
     53:   for (j=1;j<n/2;j++) {
     54:     for (i=0;i<n-j;i++) { if ((i+j)<n && i<m) A[(i+j)+i*ld]=-1.0; }
     55:   }
     56:   DSRestoreArray(ds,DS_MAT_A,&A);
     57:   DSSetState(ds,DS_STATE_RAW);
     58:   if (verbose) {
     59:     PetscViewerPushFormat(viewer,PETSC_VIEWER_ASCII_MATLAB);
     60:     PetscPrintf(PETSC_COMM_WORLD,"Initial - - - - - - - - -\n");
     61:   }
     62:   DSView(ds,viewer);

     64:   /* Solve */
     65:   PetscMalloc1(k,&w);
     66:   DSGetSlepcSC(ds,&sc);
     67:   sc->comparison    = SlepcCompareLargestReal;
     68:   sc->comparisonctx = NULL;
     69:   sc->map           = NULL;
     70:   sc->mapobj        = NULL;
     71:   DSSolve(ds,w,NULL);
     72:   DSSort(ds,w,NULL,NULL,NULL,NULL);
     73:   if (verbose) {
     74:     PetscPrintf(PETSC_COMM_WORLD,"After solve - - - - - - - - -\n");
     75:     DSView(ds,viewer);
     76:   }

     78:   /* Print singular values */
     79:   PetscPrintf(PETSC_COMM_WORLD,"Computed singular values =\n");
     80:   for (i=0;i<k;i++) {
     81:     sigma = PetscRealPart(w[i]);
     82:     PetscViewerASCIIPrintf(viewer,"  %.5f\n",(double)sigma);
     83:   }

     85:   /* Singular vectors */
     86:   DSVectors(ds,DS_MAT_U,NULL,NULL);  /* all singular vectors */
     87:   j = 0;
     88:   rnorm = 0.0;
     89:   DSGetArray(ds,DS_MAT_U,&U);
     90:   for (i=0;i<n;i++) {
     91:     aux = PetscAbsScalar(U[i+j*ld]);
     92:     rnorm += aux*aux;
     93:   }
     94:   DSRestoreArray(ds,DS_MAT_U,&U);
     95:   rnorm = PetscSqrtReal(rnorm);
     96:   PetscPrintf(PETSC_COMM_WORLD,"Norm of 1st U vector = %.3f\n",(double)rnorm);

     98:   PetscFree(w);
     99:   DSDestroy(&ds);
    100:   SlepcFinalize();
    101:   return ierr;
    102: }

    104: /*TEST

    106:    test:
    107:       suffix: 1
    108:       requires: !single

    110: TEST*/