Actual source code: test40.c

slepc-3.20.2 2024-03-15
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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[] = "Test two-sided Krylov-Schur without calling EPSSetFromOptions (based on ex5.c).\n\n"
 12:   "The command line options are:\n"
 13:   "  -m <m>, where <m> = number of grid subdivisions in each dimension.\n\n";

 15: #include <slepceps.h>

 17: /*
 18:    User-defined routines
 19: */
 20: PetscErrorCode MatMarkovModel(PetscInt m,Mat A);

 22: int main(int argc,char **argv)
 23: {
 24:   Mat            A;               /* operator matrix */
 25:   EPS            eps;             /* eigenproblem solver context */
 26:   PetscReal      tol=1000*PETSC_MACHINE_EPSILON;
 27:   PetscInt       N,m=15,nev;

 29:   PetscFunctionBeginUser;
 30:   PetscCall(SlepcInitialize(&argc,&argv,(char*)0,help));

 32:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-m",&m,NULL));
 33:   N = m*(m+1)/2;
 34:   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"\nMarkov Model, N=%" PetscInt_FMT " (m=%" PetscInt_FMT ")\n\n",N,m));

 36:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 37:      Compute the operator matrix that defines the eigensystem, Ax=kx
 38:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 40:   PetscCall(MatCreate(PETSC_COMM_WORLD,&A));
 41:   PetscCall(MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,N,N));
 42:   PetscCall(MatSetFromOptions(A));
 43:   PetscCall(MatSetUp(A));
 44:   PetscCall(MatMarkovModel(m,A));

 46:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 47:                 Create the eigensolver and set various options
 48:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 50:   PetscCall(EPSCreate(PETSC_COMM_WORLD,&eps));
 51:   PetscCall(EPSSetOperators(eps,A,NULL));
 52:   PetscCall(EPSSetProblemType(eps,EPS_NHEP));
 53:   PetscCall(EPSSetTolerances(eps,tol,PETSC_DEFAULT));
 54:   PetscCall(EPSSetDimensions(eps,4,PETSC_DEFAULT,PETSC_DEFAULT));
 55:   PetscCall(EPSSetWhichEigenpairs(eps,EPS_LARGEST_REAL));
 56:   PetscCall(EPSSetTwoSided(eps,PETSC_TRUE));

 58:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 59:                       Solve the eigensystem
 60:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 62:   PetscCall(EPSSolve(eps));
 63:   PetscCall(EPSGetDimensions(eps,&nev,NULL,NULL));
 64:   PetscCall(PetscPrintf(PETSC_COMM_WORLD," Number of requested eigenvalues: %" PetscInt_FMT "\n",nev));

 66:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 67:                     Display solution and clean up
 68:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 70:   PetscCall(EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL));
 71:   PetscCall(EPSDestroy(&eps));
 72:   PetscCall(MatDestroy(&A));
 73:   PetscCall(SlepcFinalize());
 74:   return 0;
 75: }

 77: PetscErrorCode MatMarkovModel(PetscInt m,Mat A)
 78: {
 79:   const PetscReal cst = 0.5/(PetscReal)(m-1);
 80:   PetscReal       pd,pu;
 81:   PetscInt        Istart,Iend,i,j,jmax,ix=0;

 83:   PetscFunctionBeginUser;
 84:   PetscCall(MatGetOwnershipRange(A,&Istart,&Iend));
 85:   for (i=1;i<=m;i++) {
 86:     jmax = m-i+1;
 87:     for (j=1;j<=jmax;j++) {
 88:       ix = ix + 1;
 89:       if (ix-1<Istart || ix>Iend) continue;  /* compute only owned rows */
 90:       if (j!=jmax) {
 91:         pd = cst*(PetscReal)(i+j-1);
 92:         /* north */
 93:         if (i==1) PetscCall(MatSetValue(A,ix-1,ix,2*pd,INSERT_VALUES));
 94:         else PetscCall(MatSetValue(A,ix-1,ix,pd,INSERT_VALUES));
 95:         /* east */
 96:         if (j==1) PetscCall(MatSetValue(A,ix-1,ix+jmax-1,2*pd,INSERT_VALUES));
 97:         else PetscCall(MatSetValue(A,ix-1,ix+jmax-1,pd,INSERT_VALUES));
 98:       }
 99:       /* south */
100:       pu = 0.5 - cst*(PetscReal)(i+j-3);
101:       if (j>1) PetscCall(MatSetValue(A,ix-1,ix-2,pu,INSERT_VALUES));
102:       /* west */
103:       if (i>1) PetscCall(MatSetValue(A,ix-1,ix-jmax-2,pu,INSERT_VALUES));
104:     }
105:   }
106:   PetscCall(MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY));
107:   PetscCall(MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY));
108:   PetscFunctionReturn(PETSC_SUCCESS);
109: }

111: /*TEST

113:    test:
114:       requires: !single

116: TEST*/