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[] = "Diagonal eigenproblem. Illustrates use of shell preconditioner.\n\n"
 12:   "The command line options are:\n"
 13:   "  -n <n>, where <n> = number of grid subdivisions = matrix dimension.\n"
 14:   "  -seed <s>, where <s> = seed for random number generation.\n\n";

 16: #include <slepceps.h>

 18: typedef struct {
 19:   PetscScalar target;
 20: } PCCtx;

 22: PetscErrorCode PCApply_User(PC pc,Vec x,Vec y)
 23: {
 24:   PetscInt    i,rstart,rend;
 25:   PetscScalar *yarray;
 26:   PCCtx       *ctx;

 28:   PetscFunctionBeginUser;
 29:   PetscCall(PCShellGetContext(pc,&ctx));
 30:   PetscCall(VecCopy(x,y));
 31:   PetscCall(VecGetOwnershipRange(y,&rstart,&rend));
 32:   PetscCall(VecGetArray(y,&yarray));
 33:   for (i=0;i<rend-rstart;i++) yarray[i] /= (i-rstart+1-ctx->target);
 34:   PetscCall(VecRestoreArray(y,&yarray));
 35:   PetscFunctionReturn(PETSC_SUCCESS);
 36: }

 38: int main(int argc,char **argv)
 39: {
 40:   Mat            A;           /* problem matrix */
 41:   EPS            eps;         /* eigenproblem solver context */
 42:   Vec            v0;          /* initial vector */
 43:   PetscRandom    rand;
 44:   PetscReal      tol=PETSC_SMALL;
 45:   PetscInt       n=30,i,Istart,Iend,seed=0x12345678;
 46:   ST             st;
 47:   KSP            ksp;
 48:   PC             pc;
 49:   PCCtx          ctx;

 51:   PetscFunctionBeginUser;
 52:   PetscCall(SlepcInitialize(&argc,&argv,NULL,help));

 54:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL));
 55:   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"\nDiagonal Eigenproblem, n=%" PetscInt_FMT "\n\n",n));

 57:   PetscCall(MatCreate(PETSC_COMM_WORLD,&A));
 58:   PetscCall(MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,n,n));
 59:   PetscCall(MatSetFromOptions(A));
 60:   PetscCall(MatGetOwnershipRange(A,&Istart,&Iend));
 61:   for (i=Istart;i<Iend;i++) PetscCall(MatSetValue(A,i,i,i+1,INSERT_VALUES));
 62:   PetscCall(MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY));
 63:   PetscCall(MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY));

 65:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 66:                       Solve the eigensystem
 67:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 68:   PetscCall(EPSCreate(PETSC_COMM_WORLD,&eps));
 69:   PetscCall(EPSSetOperators(eps,A,NULL));
 70:   PetscCall(EPSSetProblemType(eps,EPS_HEP));
 71:   PetscCall(EPSSetTolerances(eps,tol,PETSC_CURRENT));
 72:   PetscCall(EPSSetFromOptions(eps));
 73:   PetscCall(EPSGetST(eps,&st));
 74:   PetscCall(STGetKSP(st,&ksp));
 75:   PetscCall(KSPGetPC(ksp,&pc));
 76:   PetscCall(PCSetType(pc,PCSHELL));
 77:   PetscCall(PCShellSetApply(pc,PCApply_User));
 78:   PetscCall(EPSGetTarget(eps,&ctx.target));
 79:   PetscCall(PCShellSetContext(pc,&ctx));

 81:   /* set random initial vector */
 82:   PetscCall(MatCreateVecs(A,&v0,NULL));
 83:   PetscCall(PetscRandomCreate(PETSC_COMM_WORLD,&rand));
 84:   PetscCall(PetscRandomSetFromOptions(rand));
 85:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-seed",&seed,NULL));
 86:   PetscCall(PetscRandomSetSeed(rand,seed));
 87:   PetscCall(PetscRandomSeed(rand));
 88:   PetscCall(VecSetRandom(v0,rand));
 89:   PetscCall(EPSSetInitialSpace(eps,1,&v0));
 90:   /* call the solver */
 91:   PetscCall(EPSSolve(eps));

 93:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 94:                     Display solution and clean up
 95:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 96:   PetscCall(EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL));
 97:   PetscCall(EPSDestroy(&eps));
 98:   PetscCall(MatDestroy(&A));
 99:   PetscCall(VecDestroy(&v0));
100:   PetscCall(PetscRandomDestroy(&rand));
101:   PetscCall(SlepcFinalize());
102:   return 0;
103: }

105: /*TEST

107:    testset:
108:       args: -eps_nev 4 -eps_target 31
109:       requires: !single
110:       output_file: output/test12_1.out
111:       test:
112:          suffix: 1
113:          args: -eps_type {{krylovschur subspace arnoldi power}} -st_type sinvert
114:       test:
115:          suffix: 1_gd
116:          args: -eps_type {{gd jd}}
117:       test:
118:          suffix: 1_gd2
119:          args: -eps_type gd -eps_gd_double_expansion

121: TEST*/