Actual source code: acoustic_wave_1d.c

slepc-3.7.0 2016-05-16
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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: }