Actual source code: test4.c

slepc-3.17.0 2022-03-31
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  1: /*
  2:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  3:    SLEPc - Scalable Library for Eigenvalue Problem Computations
  4:    Copyright (c) 2002-, 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[] = "Solve a quadratic problem with PEPLINEAR with a user-provided EPS.\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 <slepcpep.h>

 18: int main(int argc,char **argv)
 19: {
 20:   Mat            M,C,K,A[3];
 21:   PEP            pep;
 22:   PetscInt       N,n=10,m,Istart,Iend,II,i,j;
 23:   PetscBool      flag,expmat;
 24:   PetscReal      alpha,beta;
 25:   EPS            eps;
 26:   ST             st;
 27:   KSP            ksp;
 28:   PC             pc;

 30:   SlepcInitialize(&argc,&argv,(char*)0,help);
 31:   PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);
 32:   PetscOptionsGetInt(NULL,NULL,"-m",&m,&flag);
 33:   if (!flag) m=n;
 34:   N = n*m;
 35:   PetscPrintf(PETSC_COMM_WORLD,"\nQuadratic Eigenproblem, N=%" PetscInt_FMT " (%" PetscInt_FMT "x%" PetscInt_FMT " grid)\n\n",N,n,m);

 37:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 38:      Compute the matrices that define the eigensystem, (k^2*M+k*C+K)x=0
 39:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 41:   /* K is the 2-D Laplacian */
 42:   MatCreate(PETSC_COMM_WORLD,&K);
 43:   MatSetSizes(K,PETSC_DECIDE,PETSC_DECIDE,N,N);
 44:   MatSetFromOptions(K);
 45:   MatSetUp(K);
 46:   MatGetOwnershipRange(K,&Istart,&Iend);
 47:   for (II=Istart;II<Iend;II++) {
 48:     i = II/n; j = II-i*n;
 49:     if (i>0) MatSetValue(K,II,II-n,-1.0,INSERT_VALUES);
 50:     if (i<m-1) MatSetValue(K,II,II+n,-1.0,INSERT_VALUES);
 51:     if (j>0) MatSetValue(K,II,II-1,-1.0,INSERT_VALUES);
 52:     if (j<n-1) MatSetValue(K,II,II+1,-1.0,INSERT_VALUES);
 53:     MatSetValue(K,II,II,4.0,INSERT_VALUES);
 54:   }
 55:   MatAssemblyBegin(K,MAT_FINAL_ASSEMBLY);
 56:   MatAssemblyEnd(K,MAT_FINAL_ASSEMBLY);

 58:   /* C is the 1-D Laplacian on horizontal lines */
 59:   MatCreate(PETSC_COMM_WORLD,&C);
 60:   MatSetSizes(C,PETSC_DECIDE,PETSC_DECIDE,N,N);
 61:   MatSetFromOptions(C);
 62:   MatSetUp(C);
 63:   MatGetOwnershipRange(C,&Istart,&Iend);
 64:   for (II=Istart;II<Iend;II++) {
 65:     i = II/n; j = II-i*n;
 66:     if (j>0) MatSetValue(C,II,II-1,-1.0,INSERT_VALUES);
 67:     if (j<n-1) MatSetValue(C,II,II+1,-1.0,INSERT_VALUES);
 68:     MatSetValue(C,II,II,2.0,INSERT_VALUES);
 69:   }
 70:   MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
 71:   MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);

 73:   /* M is a diagonal matrix */
 74:   MatCreate(PETSC_COMM_WORLD,&M);
 75:   MatSetSizes(M,PETSC_DECIDE,PETSC_DECIDE,N,N);
 76:   MatSetFromOptions(M);
 77:   MatSetUp(M);
 78:   MatGetOwnershipRange(M,&Istart,&Iend);
 79:   for (II=Istart;II<Iend;II++) MatSetValue(M,II,II,(PetscReal)(II+1),INSERT_VALUES);
 80:   MatAssemblyBegin(M,MAT_FINAL_ASSEMBLY);
 81:   MatAssemblyEnd(M,MAT_FINAL_ASSEMBLY);

 83:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 84:              Create a standalone EPS with appropriate settings
 85:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 87:   EPSCreate(PETSC_COMM_WORLD,&eps);
 88:   EPSSetWhichEigenpairs(eps,EPS_TARGET_MAGNITUDE);
 89: #if defined(PETSC_USE_COMPLEX)
 90:   EPSSetTarget(eps,0.01*PETSC_i);
 91: #endif
 92:   EPSGetST(eps,&st);
 93:   STSetType(st,STSINVERT);
 94:   STGetKSP(st,&ksp);
 95:   KSPSetType(ksp,KSPBCGS);
 96:   KSPGetPC(ksp,&pc);
 97:   PCSetType(pc,PCJACOBI);
 98:   EPSSetFromOptions(eps);

100:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
101:              Create the eigensolver and solve the eigensystem
102:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

104:   PEPCreate(PETSC_COMM_WORLD,&pep);
105:   PetscObjectSetName((PetscObject)pep,"PEP_solver");
106:   A[0] = K; A[1] = C; A[2] = M;
107:   PEPSetOperators(pep,3,A);
108:   PEPSetType(pep,PEPLINEAR);
109:   PEPSetProblemType(pep,PEP_GENERAL);
110:   PEPLinearSetEPS(pep,eps);
111:   PEPSetFromOptions(pep);
112:   PEPSolve(pep);
113:   PEPLinearGetLinearization(pep,&alpha,&beta);
114:   PetscPrintf(PETSC_COMM_WORLD," Linearization with alpha=%g, beta=%g",(double)alpha,(double)beta);
115:   PEPLinearGetExplicitMatrix(pep,&expmat);
116:   if (expmat) PetscPrintf(PETSC_COMM_WORLD," with explicit matrix");
117:   PetscPrintf(PETSC_COMM_WORLD,"\n");

119:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
120:                     Display solution and clean up
121:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

123:   PEPErrorView(pep,PEP_ERROR_BACKWARD,NULL);
124:   PEPDestroy(&pep);
125:   EPSDestroy(&eps);
126:   MatDestroy(&M);
127:   MatDestroy(&C);
128:   MatDestroy(&K);
129:   SlepcFinalize();
130:   return 0;
131: }

133: /*TEST

135:    testset:
136:       args: -pep_linear_explicitmatrix -pep_view_vectors ::ascii_info
137:       test:
138:          suffix: 1_real
139:          requires: !single !complex
140:       test:
141:          suffix: 1
142:          requires: !single complex

144: TEST*/