Date: 2026-03-09T09:12:13+00:00

Actual source code: test16.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[] = "Test pseudo-orthogonalization.\n\n";

     13: #include <slepcds.h>

     15: int main(int argc,char **argv)
     16: {
     17:   DS             ds;
     18:   PetscReal      *s,*ns;
     19:   PetscScalar    *A;
     20:   PetscInt       i,j,n=10;
     21:   PetscViewer    viewer;
     22:   PetscBool      verbose;

     24:   PetscFunctionBeginUser;
     25:   PetscCall(SlepcInitialize(&argc,&argv,NULL,help));
     26:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL));
     27:   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"Test pseudo-orthogonalization for GHIEP - dimension %" PetscInt_FMT ".\n",n));
     28:   PetscCall(PetscOptionsHasName(NULL,NULL,"-verbose",&verbose));

     30:   /* Create DS object */
     31:   PetscCall(DSCreate(PETSC_COMM_WORLD,&ds));
     32:   PetscCall(DSSetType(ds,DSGHIEP));
     33:   PetscCall(DSSetFromOptions(ds));
     34:   PetscCall(DSAllocate(ds,n));
     35:   PetscCall(DSSetDimensions(ds,n,0,0));

     37:   /* Set up viewer */
     38:   PetscCall(PetscViewerASCIIGetStdout(PETSC_COMM_WORLD,&viewer));
     39:   if (verbose) PetscCall(PetscViewerPushFormat(viewer,PETSC_VIEWER_ASCII_MATLAB));

     41:   /* Fill with a symmetric Toeplitz matrix */
     42:   PetscCall(DSGetArray(ds,DS_MAT_A,&A));
     43:   for (i=0;i<n;i++) A[i+i*n]=2.0;
     44:   for (j=1;j<3;j++) {
     45:     for (i=0;i<n-j;i++) { A[i+(i+j)*n]=1.0; A[(i+j)+i*n]=1.0; }
     46:   }
     47:   for (j=1;j<3;j++) { A[0+j*n]=-1.0*(j+2); A[j+0*n]=-1.0*(j+2); }
     48:   PetscCall(DSRestoreArray(ds,DS_MAT_A,&A));
     49:   PetscCall(DSSetState(ds,DS_STATE_RAW));
     50:   if (verbose) {
     51:     PetscCall(PetscPrintf(PETSC_COMM_WORLD,"Initial - - - - - - - - -\n"));
     52:     PetscCall(DSView(ds,viewer));
     53:   }

     55:   /* Signature matrix */
     56:   PetscCall(PetscMalloc2(n,&s,n,&ns));
     57:   s[0] = -1.0;
     58:   for (i=1;i<n-1;i++) s[i]=1.0;
     59:   s[n-1] = -1.0;

     61:   /* Orthogonalize and show signature */
     62:   PetscCall(DSPseudoOrthogonalize(ds,DS_MAT_A,n,s,NULL,ns));
     63:   if (verbose) {
     64:     PetscCall(PetscPrintf(PETSC_COMM_WORLD,"After pseudo-orthogonalize - - - - - - - - -\n"));
     65:     PetscCall(DSView(ds,viewer));
     66:   }
     67:   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"Resulting signature:\n"));
     68:   for (i=0;i<n;i++) PetscCall(PetscPrintf(PETSC_COMM_WORLD,"%g\n",(double)ns[i]));
     69:   PetscCall(PetscFree2(s,ns));

     71:   PetscCall(DSDestroy(&ds));
     72:   PetscCall(SlepcFinalize());
     73:   return 0;
     74: }

     76: /*TEST

     78:    test:
     79:       suffix: 1

     81: TEST*/