Actual source code: test2.c

slepc-3.9.2 2018-07-02
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  1: /*
  2:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  3:    SLEPc - Scalable Library for Eigenvalue Problem Computations
  4:    Copyright (c) 2002-2018, 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: */
 10: /*
 11:    Example based on spring problem in NLEVP collection [1]. See the parameters
 12:    meaning at Example 2 in [2].

 14:    [1] T. Betcke, N. J. Higham, V. Mehrmann, C. Schroder, and F. Tisseur,
 15:        NLEVP: A Collection of Nonlinear Eigenvalue Problems, MIMS EPrint
 16:        2010.98, November 2010.
 17:    [2] F. Tisseur, Backward error and condition of polynomial eigenvalue
 18:        problems, Linear Algebra and its Applications, 309 (2000), pp. 339--361,
 19:        April 2000.
 20: */

 22: static char help[] = "Test the solution of a PEP from a finite element model of "
 23:   "damped mass-spring system (problem from NLEVP collection).\n\n"
 24:   "The command line options are:\n"
 25:   "  -n <n> ... number of grid subdivisions.\n"
 26:   "  -mu <value> ... mass (default 1).\n"
 27:   "  -tau <value> ... damping constant of the dampers (default 10).\n"
 28:   "  -kappa <value> ... damping constant of the springs (default 5).\n"
 29:   "  -initv ... set an initial vector.\n\n";

 31: #include <slepcpep.h>

 33: int main(int argc,char **argv)
 34: {
 35:   Mat            M,C,K,A[3];      /* problem matrices */
 36:   PEP            pep;             /* polynomial eigenproblem solver context */
 38:   PetscInt       n=30,Istart,Iend,i,nev;
 39:   PetscScalar    mu=1.0,tau=10.0,kappa=5.0;
 40:   PetscBool      initv=PETSC_FALSE;
 41:   Vec            v0;

 43:   SlepcInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;

 45:   PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);
 46:   PetscOptionsGetScalar(NULL,NULL,"-mu",&mu,NULL);
 47:   PetscOptionsGetScalar(NULL,NULL,"-tau",&tau,NULL);
 48:   PetscOptionsGetScalar(NULL,NULL,"-kappa",&kappa,NULL);
 49:   PetscOptionsGetBool(NULL,NULL,"-initv",&initv,NULL);

 51:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 52:      Compute the matrices that define the eigensystem, (k^2*M+k*C+K)x=0
 53:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 55:   /* K is a tridiagonal */
 56:   MatCreate(PETSC_COMM_WORLD,&K);
 57:   MatSetSizes(K,PETSC_DECIDE,PETSC_DECIDE,n,n);
 58:   MatSetFromOptions(K);
 59:   MatSetUp(K);

 61:   MatGetOwnershipRange(K,&Istart,&Iend);
 62:   for (i=Istart;i<Iend;i++) {
 63:     if (i>0) {
 64:       MatSetValue(K,i,i-1,-kappa,INSERT_VALUES);
 65:     }
 66:     MatSetValue(K,i,i,kappa*3.0,INSERT_VALUES);
 67:     if (i<n-1) {
 68:       MatSetValue(K,i,i+1,-kappa,INSERT_VALUES);
 69:     }
 70:   }

 72:   MatAssemblyBegin(K,MAT_FINAL_ASSEMBLY);
 73:   MatAssemblyEnd(K,MAT_FINAL_ASSEMBLY);

 75:   /* C is a tridiagonal */
 76:   MatCreate(PETSC_COMM_WORLD,&C);
 77:   MatSetSizes(C,PETSC_DECIDE,PETSC_DECIDE,n,n);
 78:   MatSetFromOptions(C);
 79:   MatSetUp(C);

 81:   MatGetOwnershipRange(C,&Istart,&Iend);
 82:   for (i=Istart;i<Iend;i++) {
 83:     if (i>0) {
 84:       MatSetValue(C,i,i-1,-tau,INSERT_VALUES);
 85:     }
 86:     MatSetValue(C,i,i,tau*3.0,INSERT_VALUES);
 87:     if (i<n-1) {
 88:       MatSetValue(C,i,i+1,-tau,INSERT_VALUES);
 89:     }
 90:   }

 92:   MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
 93:   MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);

 95:   /* M is a diagonal matrix */
 96:   MatCreate(PETSC_COMM_WORLD,&M);
 97:   MatSetSizes(M,PETSC_DECIDE,PETSC_DECIDE,n,n);
 98:   MatSetFromOptions(M);
 99:   MatSetUp(M);
100:   MatGetOwnershipRange(M,&Istart,&Iend);
101:   for (i=Istart;i<Iend;i++) {
102:     MatSetValue(M,i,i,mu,INSERT_VALUES);
103:   }
104:   MatAssemblyBegin(M,MAT_FINAL_ASSEMBLY);
105:   MatAssemblyEnd(M,MAT_FINAL_ASSEMBLY);

107:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
108:                 Create the eigensolver and set various options
109:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

111:   PEPCreate(PETSC_COMM_WORLD,&pep);
112:   A[0] = K; A[1] = C; A[2] = M;
113:   PEPSetOperators(pep,3,A);
114:   PEPSetProblemType(pep,PEP_GENERAL);
115:   PEPSetTolerances(pep,PETSC_SMALL,PETSC_DEFAULT);
116:   if (initv) { /* initial vector */
117:     MatCreateVecs(K,&v0,NULL);
118:     VecSetValue(v0,0,-1.0,INSERT_VALUES);
119:     VecSetValue(v0,1,0.5,INSERT_VALUES);
120:     VecAssemblyBegin(v0);
121:     VecAssemblyEnd(v0);
122:     PEPSetInitialSpace(pep,1,&v0);
123:     VecDestroy(&v0);
124:   }
125:   PEPSetFromOptions(pep);

127:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
128:                       Solve the eigensystem
129:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

131:   PEPSolve(pep);
132:   PEPGetDimensions(pep,&nev,NULL,NULL);
133:   PetscPrintf(PETSC_COMM_WORLD," Number of requested eigenvalues: %D\n",nev);

135:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
136:                     Display solution and clean up
137:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

139:   PEPErrorView(pep,PEP_ERROR_BACKWARD,NULL);
140:   PEPDestroy(&pep);
141:   MatDestroy(&M);
142:   MatDestroy(&C);
143:   MatDestroy(&K);
144:   SlepcFinalize();
145:   return ierr;
146: }