Date: 2021-02-01T14:42:01+00:00

Actual source code: test27.c
slepc-3.14.2 2021-02-01
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      1: /*
      2:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      3:    SLEPc - Scalable Library for Eigenvalue Problem Computations
      4:    Copyright (c) 2002-2020, 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[] = "Illustrates feeding exact eigenvectors as initial vectors of a second solve.\n\n"
     12:   "Based on ex2.\n"
     13:   "The command line options are:\n"
     14:   "  -n <n>, where <n> = number of grid subdivisions in x dimension.\n"
     15:   "  -m <m>, where <m> = number of grid subdivisions in y dimension.\n\n";

     17: #include <slepceps.h>

     19: int main(int argc,char **argv)
     20: {
     21:   Mat            A;
     22:   EPS            eps;
     23:   PetscInt       N,n=10,m,Istart,Iend,II,nev,nconv,i,j,neigs=5;
     24:   PetscBool      flag,terse;
     26:   Vec            v,*X;

     28:   SlepcInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;
     29:   PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);
     30:   PetscOptionsGetInt(NULL,NULL,"-m",&m,&flag);
     31:   if (!flag) m=n;
     32:   N = n*m;
     33:   PetscOptionsGetInt(NULL,NULL,"-neigs",&neigs,NULL);
     34:   PetscPrintf(PETSC_COMM_WORLD,"\n2-D Laplacian Eigenproblem, N=%D (%Dx%D grid), neigs=%D\n\n",N,n,m,neigs);

     36:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     37:                     Create the 2-D Laplacian
     38:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     40:   MatCreate(PETSC_COMM_WORLD,&A);
     41:   MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,N,N);
     42:   MatSetFromOptions(A);
     43:   MatSetUp(A);
     44:   MatGetOwnershipRange(A,&Istart,&Iend);
     45:   for (II=Istart;II<Iend;II++) {
     46:     i = II/n; j = II-i*n;
     47:     if (i>0) { MatSetValue(A,II,II-n,-1.0,INSERT_VALUES); }
     48:     if (i<m-1) { MatSetValue(A,II,II+n,-1.0,INSERT_VALUES); }
     49:     if (j>0) { MatSetValue(A,II,II-1,-1.0,INSERT_VALUES); }
     50:     if (j<n-1) { MatSetValue(A,II,II+1,-1.0,INSERT_VALUES); }
     51:     MatSetValue(A,II,II,4.0,INSERT_VALUES);
     52:   }
     53:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
     54:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
     55:   MatCreateVecs(A,&v,NULL);

     57:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     58:                 Create the eigensolver and set various options
     59:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     61:   EPSCreate(PETSC_COMM_WORLD,&eps);
     62:   EPSSetOperators(eps,A,NULL);
     63:   EPSSetProblemType(eps,EPS_HEP);
     64:   EPSSetWhichEigenpairs(eps,EPS_SMALLEST_REAL);
     65:   EPSSetDimensions(eps,neigs,PETSC_DEFAULT,PETSC_DEFAULT);
     66:   EPSSetFromOptions(eps);

     68:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     69:                 Solve the eigensystem for the first time
     70:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     72:   EPSSolve(eps);
     73:   EPSGetDimensions(eps,&nev,NULL,NULL);
     74:   PetscPrintf(PETSC_COMM_WORLD," Number of requested eigenvalues: %D\n",nev);

     76:   EPSGetConverged(eps,&nconv);
     77:   if (nconv<neigs) SETERRQ2(PETSC_COMM_WORLD,1,"Only %D eigenvalues have converged, %D requested",nconv,neigs);
     78:   VecDuplicateVecs(v,neigs,&X);
     79:   for (i=0;i<neigs;i++) {
     80:     EPSGetEigenvector(eps,i,X[i],NULL);
     81:   }

     83:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     84:                     Display solution of first solve
     85:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     87:   PetscOptionsHasName(NULL,NULL,"-terse",&terse);
     88:   if (terse) {
     89:     EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL);
     90:   } else {
     91:     PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO_DETAIL);
     92:     EPSConvergedReasonView(eps,PETSC_VIEWER_STDOUT_WORLD);
     93:     EPSErrorView(eps,EPS_ERROR_RELATIVE,PETSC_VIEWER_STDOUT_WORLD);
     94:     PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD);
     95:   }

     97:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     98:           Solve the eigensystem again, feeding the initial vectors
     99:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    101:   PetscPrintf(PETSC_COMM_WORLD," Solving again with eigenvectors as initial guesses\n");
    102:   EPSSetInitialSpace(eps,neigs,X);
    103:   EPSSolve(eps);

    105:   if (terse) {
    106:     EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL);
    107:   } else {
    108:     PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO_DETAIL);
    109:     EPSConvergedReasonView(eps,PETSC_VIEWER_STDOUT_WORLD);
    110:     EPSErrorView(eps,EPS_ERROR_RELATIVE,PETSC_VIEWER_STDOUT_WORLD);
    111:     PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD);
    112:   }

    114:   VecDestroy(&v);
    115:   VecDestroyVecs(neigs,&X);
    116:   EPSDestroy(&eps);
    117:   MatDestroy(&A);
    118:   SlepcFinalize();
    119:   return ierr;
    120: }

    122: /*TEST

    124:    test:
    125:       suffix: 1
    126:       args: -eps_type {{gd jd rqcg lobpcg}} -terse

    128:    test:
    129:       suffix: 2
    130:       args: -eps_interval .17,1.3 -st_type filter -st_filter_degree 150 -eps_nev 1 -terse
    131:       filter: grep -v "requested"
    132:       requires: !single

    134: TEST*/