Actual source code: test27.c

slepc-3.17.2 2022-08-09
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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[] = "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;
 25:   Vec            v,*X;

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

 35:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 36:                     Create the 2-D Laplacian
 37:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

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

 56:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 57:                 Create the eigensolver and set various options
 58:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

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

 67:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 68:                 Solve the eigensystem for the first time
 69:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

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

 75:   EPSGetConverged(eps,&nconv);
 77:   VecDuplicateVecs(v,neigs,&X);
 78:   for (i=0;i<neigs;i++) EPSGetEigenvector(eps,i,X[i],NULL);

 80:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 81:                     Display solution of first solve
 82:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

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

 93:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 94:           Solve the eigensystem again, feeding the initial vectors
 95:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 97:   PetscPrintf(PETSC_COMM_WORLD," Solving again with eigenvectors as initial guesses\n");
 98:   EPSSetInitialSpace(eps,neigs,X);
 99:   EPSSolve(eps);

101:   if (terse) EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL);
102:   else {
103:     PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO_DETAIL);
104:     EPSConvergedReasonView(eps,PETSC_VIEWER_STDOUT_WORLD);
105:     EPSErrorView(eps,EPS_ERROR_RELATIVE,PETSC_VIEWER_STDOUT_WORLD);
106:     PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD);
107:   }

109:   VecDestroy(&v);
110:   VecDestroyVecs(neigs,&X);
111:   EPSDestroy(&eps);
112:   MatDestroy(&A);
113:   SlepcFinalize();
114:   return 0;
115: }

117: /*TEST

119:    test:
120:       suffix: 1
121:       args: -eps_type {{gd jd rqcg lobpcg}} -terse

123:    testset:
124:       args: -eps_interval .17,1.3 -terse
125:       filter: grep -v "requested"
126:       output_file: output/test27_2.out
127:       test:
128:          suffix: 2
129:          args: -st_type filter -st_filter_degree 150 -eps_nev 1
130:          requires: !single
131:       test:
132:          suffix: 2_evsl
133:          nsize: {{1 2}}
134:          args: -eps_type evsl
135:          requires: evsl

137: TEST*/