Actual source code: ex46.c

slepc-3.16.0 2021-09-30
Report Typos and Errors
  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[] = "Illustrates passing a sparser matrix to build the preconditioner.\n\n"
 12:   "The command line options are:\n"
 13:   "  -n <n>, where <n> = number of grid subdivisions in x dimension.\n"
 14:   "  -m <m>, where <m> = number of grid subdivisions in y dimension.\n\n";

 16: #include <slepceps.h>

 18: int main(int argc,char **argv)
 19: {
 20:   Mat            A,A0;            /* operator matrix */
 21:   EPS            eps;             /* eigenproblem solver context */
 22:   ST             st;
 23:   PetscInt       N,n=24,m,Istart,Iend,II,i,j;
 24:   PetscBool      flag,terse;

 27:   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:   PetscPrintf(PETSC_COMM_WORLD,"\nModified 2-D Laplacian Eigenproblem, N=%D (%Dx%D grid)\n\n",N,n,m);

 35:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 36:        Compute the operator matrix A and a sparser approximation A0
 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,-0.2,INSERT_VALUES); }
 47:     if (i<m-1) { MatSetValue(A,II,II+n,-0.2,INSERT_VALUES); }
 48:     if (j>0) { MatSetValue(A,II,II-1,-3.0,INSERT_VALUES); }
 49:     if (j<n-1) { MatSetValue(A,II,II+1,-3.0,INSERT_VALUES); }
 50:     MatSetValue(A,II,II,7.0,INSERT_VALUES);
 51:   }
 52:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
 53:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);

 55:   MatCreate(PETSC_COMM_WORLD,&A0);
 56:   MatSetSizes(A0,PETSC_DECIDE,PETSC_DECIDE,N,N);
 57:   MatSetFromOptions(A0);
 58:   MatSetUp(A0);
 59:   MatGetOwnershipRange(A0,&Istart,&Iend);
 60:   for (II=Istart;II<Iend;II++) {
 61:     i = II/n; j = II-i*n;
 62:     if (j>0) { MatSetValue(A0,II,II-1,-3.0,INSERT_VALUES); }
 63:     if (j<n-1) { MatSetValue(A0,II,II+1,-3.0,INSERT_VALUES); }
 64:     MatSetValue(A0,II,II,7.0,INSERT_VALUES);
 65:   }
 66:   MatAssemblyBegin(A0,MAT_FINAL_ASSEMBLY);
 67:   MatAssemblyEnd(A0,MAT_FINAL_ASSEMBLY);

 69:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 70:                 Create the eigensolver and set various options
 71:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 73:   EPSCreate(PETSC_COMM_WORLD,&eps);
 74:   EPSSetOperators(eps,A,NULL);
 75:   EPSSetProblemType(eps,EPS_HEP);
 76:   EPSGetST(eps,&st);
 77:   STSetType(st,STSINVERT);
 78:   STSetPreconditionerMat(st,A0);
 79:   EPSSetTarget(eps,0.0);
 80:   EPSSetWhichEigenpairs(eps,EPS_TARGET_MAGNITUDE);
 81:   EPSSetFromOptions(eps);

 83:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 84:                  Solve the eigensystem and display solution
 85:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 87:   EPSSolve(eps);

 89:   /* show detailed info unless -terse option is given by user */
 90:   PetscOptionsHasName(NULL,NULL,"-terse",&terse);
 91:   if (terse) {
 92:     EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL);
 93:   } else {
 94:     PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO_DETAIL);
 95:     EPSConvergedReasonView(eps,PETSC_VIEWER_STDOUT_WORLD);
 96:     EPSErrorView(eps,EPS_ERROR_RELATIVE,PETSC_VIEWER_STDOUT_WORLD);
 97:     PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD);
 98:   }
 99:   EPSDestroy(&eps);
100:   MatDestroy(&A);
101:   MatDestroy(&A0);
102:   SlepcFinalize();
103:   return ierr;
104: }

106: /*TEST

108:    testset:
109:       args: -eps_nev 4 -terse
110:       output_file: output/ex46_1.out
111:       requires: !single
112:       test:
113:          suffix: 1
114:       test:
115:          suffix: 2
116:          args: -st_ksp_type bcgs -st_pc_type bjacobi

118: TEST*/