Date: 2022-03-31T15:28:53+00:00

Actual source code: test9.c
slepc-3.17.0 2022-03-31
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      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[] = "Test DSGHEP.\n\n";

     13: #include <slepcds.h>

     15: /*
     16:    Compute the norm of the j-th column of matrix mat in ds
     17:  */
     18: PetscErrorCode ComputeNorm(DS ds,DSMatType mat,PetscInt j,PetscReal *onrm)
     19: {
     20:   PetscScalar    *X;
     21:   PetscReal      aux,nrm=0.0;
     22:   PetscInt       i,n,ld;

     25:   DSGetLeadingDimension(ds,&ld);
     26:   DSGetDimensions(ds,&n,NULL,NULL,NULL);
     27:   DSGetArray(ds,mat,&X);
     28:   for (i=0;i<n;i++) {
     29:     aux = PetscAbsScalar(X[i+j*ld]);
     30:     nrm += aux*aux;
     31:   }
     32:   DSRestoreArray(ds,mat,&X);
     33:   *onrm = PetscSqrtReal(nrm);
     34:   PetscFunctionReturn(0);
     35: }

     37: int main(int argc,char **argv)
     38: {
     39:   DS             ds;
     40:   SlepcSC        sc;
     41:   PetscReal      re;
     42:   PetscScalar    *A,*B,*eig;
     43:   PetscReal      nrm;
     44:   PetscInt       i,j,n=10,ld;
     45:   PetscViewer    viewer;
     46:   PetscBool      verbose;

     48:   SlepcInitialize(&argc,&argv,(char*)0,help);
     49:   PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);
     50:   PetscPrintf(PETSC_COMM_WORLD,"Solve a System of type GHEP - dimension %" PetscInt_FMT ".\n",n);
     51:   PetscOptionsHasName(NULL,NULL,"-verbose",&verbose);

     53:   /* Create DS object */
     54:   DSCreate(PETSC_COMM_WORLD,&ds);
     55:   DSSetType(ds,DSGHEP);
     56:   DSSetFromOptions(ds);
     57:   ld = n+2;  /* test leading dimension larger than n */
     58:   DSAllocate(ds,ld);
     59:   DSSetDimensions(ds,n,0,0);

     61:   /* Set up viewer */
     62:   PetscViewerASCIIGetStdout(PETSC_COMM_WORLD,&viewer);
     63:   PetscViewerPushFormat(viewer,PETSC_VIEWER_ASCII_INFO_DETAIL);
     64:   DSView(ds,viewer);
     65:   PetscViewerPopFormat(viewer);
     66:   if (verbose) PetscViewerPushFormat(viewer,PETSC_VIEWER_ASCII_MATLAB);

     68:   /* Fill with a symmetric Toeplitz matrix */
     69:   DSGetArray(ds,DS_MAT_A,&A);
     70:   DSGetArray(ds,DS_MAT_B,&B);
     71:   for (i=0;i<n;i++) A[i+i*ld]=2.0;
     72:   for (j=1;j<3;j++) {
     73:     for (i=0;i<n-j;i++) { A[i+(i+j)*ld]=1.0; A[(i+j)+i*ld]=1.0; }
     74:   }
     75:   for (j=1;j<3;j++) { A[0+j*ld]=-1.0*(j+2); A[j+0*ld]=-1.0*(j+2); }
     76:   /* Diagonal matrix */
     77:   for (i=0;i<n;i++) B[i+i*ld]=0.1*(i+1);
     78:   DSRestoreArray(ds,DS_MAT_A,&A);
     79:   DSRestoreArray(ds,DS_MAT_B,&B);
     80:   DSSetState(ds,DS_STATE_RAW);
     81:   if (verbose) {
     82:     PetscPrintf(PETSC_COMM_WORLD,"Initial - - - - - - - - -\n");
     83:     DSView(ds,viewer);
     84:   }

     86:   /* Solve */
     87:   PetscMalloc1(n,&eig);
     88:   PetscNew(&sc);
     89:   sc->comparison    = SlepcCompareLargestMagnitude;
     90:   sc->comparisonctx = NULL;
     91:   sc->map           = NULL;
     92:   sc->mapobj        = NULL;
     93:   DSSetSlepcSC(ds,sc);
     94:   DSSolve(ds,eig,NULL);
     95:   DSSort(ds,eig,NULL,NULL,NULL,NULL);
     96:   if (verbose) {
     97:     PetscPrintf(PETSC_COMM_WORLD,"After solve - - - - - - - - -\n");
     98:     DSView(ds,viewer);
     99:   }

    101:   /* Print eigenvalues */
    102:   PetscPrintf(PETSC_COMM_WORLD,"Computed eigenvalues =\n");
    103:   for (i=0;i<n;i++) {
    104:     re = PetscRealPart(eig[i]);
    105:     PetscViewerASCIIPrintf(viewer,"  %.5f\n",(double)re);
    106:   }

    108:   /* Eigenvectors */
    109:   j = 0;
    110:   DSVectors(ds,DS_MAT_X,&j,NULL);  /* all eigenvectors */
    111:   ComputeNorm(ds,DS_MAT_X,0,&nrm);
    112:   PetscPrintf(PETSC_COMM_WORLD,"Norm of 1st vector = %.3f\n",(double)nrm);
    113:   DSVectors(ds,DS_MAT_X,NULL,NULL);  /* all eigenvectors */
    114:   if (verbose) {
    115:     PetscPrintf(PETSC_COMM_WORLD,"After vectors - - - - - - - - -\n");
    116:     DSView(ds,viewer);
    117:   }

    119:   PetscFree(eig);
    120:   PetscFree(sc);
    121:   DSDestroy(&ds);
    122:   SlepcFinalize();
    123:   return 0;
    124: }

    126: /*TEST

    128:    test:
    129:       suffix: 1
    130:       requires: !single

    132: TEST*/