Date: 2016-09-29T11:11:54+00:00

Actual source code: ex2.c
slepc-3.7.3 2016-09-29
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      1: /*
      2:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      3:    SLEPc - Scalable Library for Eigenvalue Problem Computations
      4:    Copyright (c) 2002-2016, Universitat Politecnica de Valencia, Spain

      6:    This file is part of SLEPc.

      8:    SLEPc is free software: you can redistribute it and/or modify it under  the
      9:    terms of version 3 of the GNU Lesser General Public License as published by
     10:    the Free Software Foundation.

     12:    SLEPc  is  distributed in the hope that it will be useful, but WITHOUT  ANY
     13:    WARRANTY;  without even the implied warranty of MERCHANTABILITY or  FITNESS
     14:    FOR  A  PARTICULAR PURPOSE. See the GNU Lesser General Public  License  for
     15:    more details.

     17:    You  should have received a copy of the GNU Lesser General  Public  License
     18:    along with SLEPc. If not, see <http://www.gnu.org/licenses/>.
     19:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     20: */

     22: static char help[] = "Standard symmetric eigenproblem corresponding to the Laplacian operator in 2 dimensions.\n\n"
     23:   "The command line options are:\n"
     24:   "  -n <n>, where <n> = number of grid subdivisions in x dimension.\n"
     25:   "  -m <m>, where <m> = number of grid subdivisions in y dimension.\n\n";

     27: #include <slepceps.h>

     31: int main(int argc,char **argv)
     32: {
     33:   Mat            A;               /* operator matrix */
     34:   EPS            eps;             /* eigenproblem solver context */
     35:   EPSType        type;
     36:   PetscInt       N,n=10,m,Istart,Iend,II,nev,i,j;
     37:   PetscBool      flag,terse;

     40:   SlepcInitialize(&argc,&argv,(char*)0,help);

     42:   PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);
     43:   PetscOptionsGetInt(NULL,NULL,"-m",&m,&flag);
     44:   if (!flag) m=n;
     45:   N = n*m;
     46:   PetscPrintf(PETSC_COMM_WORLD,"\n2-D Laplacian Eigenproblem, N=%D (%Dx%D grid)\n\n",N,n,m);

     48:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     49:      Compute the operator matrix that defines the eigensystem, Ax=kx
     50:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     52:   MatCreate(PETSC_COMM_WORLD,&A);
     53:   MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,N,N);
     54:   MatSetFromOptions(A);
     55:   MatSetUp(A);

     57:   MatGetOwnershipRange(A,&Istart,&Iend);
     58:   for (II=Istart;II<Iend;II++) {
     59:     i = II/n; j = II-i*n;
     60:     if (i>0) { MatSetValue(A,II,II-n,-1.0,INSERT_VALUES); }
     61:     if (i<m-1) { MatSetValue(A,II,II+n,-1.0,INSERT_VALUES); }
     62:     if (j>0) { MatSetValue(A,II,II-1,-1.0,INSERT_VALUES); }
     63:     if (j<n-1) { MatSetValue(A,II,II+1,-1.0,INSERT_VALUES); }
     64:     MatSetValue(A,II,II,4.0,INSERT_VALUES);
     65:   }

     67:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
     68:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);

     70:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     71:                 Create the eigensolver and set various options
     72:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     74:   /*
     75:      Create eigensolver context
     76:   */
     77:   EPSCreate(PETSC_COMM_WORLD,&eps);

     79:   /*
     80:      Set operators. In this case, it is a standard eigenvalue problem
     81:   */
     82:   EPSSetOperators(eps,A,NULL);
     83:   EPSSetProblemType(eps,EPS_HEP);

     85:   /*
     86:      Set solver parameters at runtime
     87:   */
     88:   EPSSetFromOptions(eps);

     90:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     91:                       Solve the eigensystem
     92:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     94:   EPSSolve(eps);

     96:   /*
     97:      Optional: Get some information from the solver and display it
     98:   */
     99:   EPSGetType(eps,&type);
    100:   PetscPrintf(PETSC_COMM_WORLD," Solution method: %s\n\n",type);
    101:   EPSGetDimensions(eps,&nev,NULL,NULL);
    102:   PetscPrintf(PETSC_COMM_WORLD," Number of requested eigenvalues: %D\n",nev);

    104:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    105:                     Display solution and clean up
    106:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    108:   /* show detailed info unless -terse option is given by user */
    109:   PetscOptionsHasName(NULL,NULL,"-terse",&terse);
    110:   if (terse) {
    111:     EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL);
    112:   } else {
    113:     PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO_DETAIL);
    114:     EPSReasonView(eps,PETSC_VIEWER_STDOUT_WORLD);
    115:     EPSErrorView(eps,EPS_ERROR_RELATIVE,PETSC_VIEWER_STDOUT_WORLD);
    116:     PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD);
    117:   }
    118:   EPSDestroy(&eps);
    119:   MatDestroy(&A);
    120:   SlepcFinalize();
    121:   return ierr;
    122: }