Date: 2017-05-17T08:27:07+00:00

Actual source code: acoustic_wave_1d.c
slepc-3.7.4 2017-05-17
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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: */
     21: /*
     22:    This example implements one of the problems found at
     23:        NLEVP: A Collection of Nonlinear Eigenvalue Problems,
     24:        The University of Manchester.
     25:    The details of the collection can be found at:
     26:        [1] T. Betcke et al., "NLEVP: A Collection of Nonlinear Eigenvalue
     27:            Problems", ACM Trans. Math. Software 39(2), Article 7, 2013.

     29:    The acoustic_wave_1d problem is a QEP from an acoustics application.
     30:    Here we solve it with the eigenvalue scaled by the imaginary unit, to be
     31:    able to use real arithmetic, so the computed eigenvalues should be scaled
     32:    back.
     33: */

     35: static char help[] = "Quadratic eigenproblem from an acoustics application (1-D).\n\n"
     36:   "The command line options are:\n"
     37:   "  -n <n>, where <n> = dimension of the matrices.\n"
     38:   "  -z <z>, where <z> = impedance (default 1.0).\n\n";

     40: #include <slepcpep.h>

     44: int main(int argc,char **argv)
     45: {
     46:   Mat            M,C,K,A[3];      /* problem matrices */
     47:   PEP            pep;             /* polynomial eigenproblem solver context */
     48:   PetscInt       n=10,Istart,Iend,i;
     49:   PetscScalar    z=1.0;
     50:   char           str[50];
     51:   PetscBool      terse;

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

     56:   PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);
     57:   PetscOptionsGetScalar(NULL,NULL,"-z",&z,NULL);
     58:   SlepcSNPrintfScalar(str,50,z,PETSC_FALSE);
     59:   PetscPrintf(PETSC_COMM_WORLD,"\nAcoustic wave 1-D, n=%D z=%s\n\n",n,str);

     61:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     62:      Compute the matrices that define the eigensystem, (k^2*M+k*C+K)x=0
     63:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     65:   /* K is a tridiagonal */
     66:   MatCreate(PETSC_COMM_WORLD,&K);
     67:   MatSetSizes(K,PETSC_DECIDE,PETSC_DECIDE,n,n);
     68:   MatSetFromOptions(K);
     69:   MatSetUp(K);
     70:
     71:   MatGetOwnershipRange(K,&Istart,&Iend);
     72:   for (i=Istart;i<Iend;i++) {
     73:     if (i>0) {
     74:       MatSetValue(K,i,i-1,-1.0*n,INSERT_VALUES);
     75:     }
     76:     if (i<n-1) {
     77:       MatSetValue(K,i,i,2.0*n,INSERT_VALUES);
     78:       MatSetValue(K,i,i+1,-1.0*n,INSERT_VALUES);
     79:     } else {
     80:       MatSetValue(K,i,i,1.0*n,INSERT_VALUES);
     81:     }
     82:   }

     84:   MatAssemblyBegin(K,MAT_FINAL_ASSEMBLY);
     85:   MatAssemblyEnd(K,MAT_FINAL_ASSEMBLY);

     87:   /* C is the zero matrix but one element*/
     88:   MatCreate(PETSC_COMM_WORLD,&C);
     89:   MatSetSizes(C,PETSC_DECIDE,PETSC_DECIDE,n,n);
     90:   MatSetFromOptions(C);
     91:   MatSetUp(C);

     93:   MatGetOwnershipRange(C,&Istart,&Iend);
     94:   if (n-1>=Istart && n-1<Iend) {
     95:     MatSetValue(C,n-1,n-1,-2*PETSC_PI/z,INSERT_VALUES);
     96:   }
     97:   MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
     98:   MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);
     99:
    100:   /* M is a diagonal matrix */
    101:   MatCreate(PETSC_COMM_WORLD,&M);
    102:   MatSetSizes(M,PETSC_DECIDE,PETSC_DECIDE,n,n);
    103:   MatSetFromOptions(M);
    104:   MatSetUp(M);

    106:   MatGetOwnershipRange(M,&Istart,&Iend);
    107:   for (i=Istart;i<Iend;i++) {
    108:     if (i<n-1) {
    109:       MatSetValue(M,i,i,4*PETSC_PI*PETSC_PI/n,INSERT_VALUES);
    110:     } else {
    111:       MatSetValue(M,i,i,2*PETSC_PI*PETSC_PI/n,INSERT_VALUES);
    112:     }
    113:   }
    114:   MatAssemblyBegin(M,MAT_FINAL_ASSEMBLY);
    115:   MatAssemblyEnd(M,MAT_FINAL_ASSEMBLY);
    116:
    117:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    118:                 Create the eigensolver and solve the problem
    119:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    121:   PEPCreate(PETSC_COMM_WORLD,&pep);
    122:   A[0] = K; A[1] = C; A[2] = M;
    123:   PEPSetOperators(pep,3,A);
    124:   PEPSetFromOptions(pep);
    125:   PEPSolve(pep);

    127:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    128:                     Display solution and clean up
    129:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
    130:
    131:   /* show detailed info unless -terse option is given by user */
    132:   PetscOptionsHasName(NULL,NULL,"-terse",&terse);
    133:   if (terse) {
    134:     PEPErrorView(pep,PEP_ERROR_BACKWARD,NULL);
    135:   } else {
    136:     PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO_DETAIL);
    137:     PEPReasonView(pep,PETSC_VIEWER_STDOUT_WORLD);
    138:     PEPErrorView(pep,PEP_ERROR_BACKWARD,PETSC_VIEWER_STDOUT_WORLD);
    139:     PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD);
    140:   }
    141:   PEPDestroy(&pep);
    142:   MatDestroy(&M);
    143:   MatDestroy(&C);
    144:   MatDestroy(&K);
    145:   SlepcFinalize();
    146:   return ierr;
    147: }