Date: 2021-09-20T09:43:48+00:00

Actual source code: test6.c
slepc-3.15.2 2021-09-20
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      1: /*
      2:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      3:    SLEPc - Scalable Library for Eigenvalue Problem Computations
      4:    Copyright (c) 2002-2021, 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 STPRECOND operations.\n\n";

     13: #include <slepcst.h>

     15: int main(int argc,char **argv)
     16: {
     17:   Mat            A,P,mat[1];
     18:   ST             st;
     19:   KSP            ksp;
     20:   Vec            v,w;
     21:   PetscScalar    sigma;
     22:   PetscInt       n=10,i,Istart,Iend;

     25:   SlepcInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;
     26:   PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);
     27:   PetscPrintf(PETSC_COMM_WORLD,"\nPreconditioner for 1-D Laplacian, n=%D\n\n",n);

     29:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     30:              Compute the operator matrix for the 1-D Laplacian
     31:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     33:   MatCreate(PETSC_COMM_WORLD,&A);
     34:   MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,n,n);
     35:   MatSetFromOptions(A);
     36:   MatSetUp(A);

     38:   MatGetOwnershipRange(A,&Istart,&Iend);
     39:   for (i=Istart;i<Iend;i++) {
     40:     if (i>0) { MatSetValue(A,i,i-1,-1.0,INSERT_VALUES); }
     41:     if (i<n-1) { MatSetValue(A,i,i+1,-1.0,INSERT_VALUES); }
     42:     MatSetValue(A,i,i,2.0,INSERT_VALUES);
     43:   }
     44:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
     45:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
     46:   MatCreateVecs(A,&v,&w);
     47:   VecSet(v,1.0);

     49:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     50:                 Create the spectral transformation object
     51:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     53:   STCreate(PETSC_COMM_WORLD,&st);
     54:   mat[0] = A;
     55:   STSetMatrices(st,1,mat);
     56:   STSetType(st,STPRECOND);
     57:   STGetKSP(st,&ksp);
     58:   KSPSetType(ksp,KSPPREONLY);
     59:   STSetFromOptions(st);

     61:   /* set up */
     62:   /* - the transform flag is necessary so that A-sigma*I is built explicitly */
     63:   STSetTransform(st,PETSC_TRUE);
     64:   /* - the ksphasmat flag is necessary when using STApply(), otherwise can only use PCApply() */
     65:   STPrecondSetKSPHasMat(st,PETSC_TRUE);
     66:   /* no need to call STSetUp() explicitly */
     67:   STSetUp(st);

     69:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     70:                        Apply the preconditioner
     71:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     73:   /* default shift */
     74:   PetscPrintf(PETSC_COMM_WORLD,"With default shift\n");
     75:   STApply(st,v,w);
     76:   VecView(w,NULL);

     78:   /* change shift */
     79:   sigma = 0.1;
     80:   STSetShift(st,sigma);
     81:   STGetShift(st,&sigma);
     82:   PetscPrintf(PETSC_COMM_WORLD,"With shift=%g\n",(double)PetscRealPart(sigma));
     83:   STApply(st,v,w);
     84:   VecView(w,NULL);
     85:   STPostSolve(st);   /* undo changes if inplace */

     87:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     88:                  Test a user-provided preconditioner matrix
     89:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     91:   MatCreate(PETSC_COMM_WORLD,&P);
     92:   MatSetSizes(P,PETSC_DECIDE,PETSC_DECIDE,n,n);
     93:   MatSetFromOptions(P);
     94:   MatSetUp(P);

     96:   MatGetOwnershipRange(P,&Istart,&Iend);
     97:   for (i=Istart;i<Iend;i++) {
     98:     MatSetValue(P,i,i,2.0,INSERT_VALUES);
     99:   }
    100:   if (Istart==0) {
    101:     MatSetValue(P,1,0,-1.0,INSERT_VALUES);
    102:     MatSetValue(P,0,1,-1.0,INSERT_VALUES);
    103:   }
    104:   MatAssemblyBegin(P,MAT_FINAL_ASSEMBLY);
    105:   MatAssemblyEnd(P,MAT_FINAL_ASSEMBLY);

    107:   /* apply new preconditioner */
    108:   STSetPreconditionerMat(st,P);
    109:   PetscPrintf(PETSC_COMM_WORLD,"With user-provided matrix\n");
    110:   STApply(st,v,w);
    111:   VecView(w,NULL);

    113:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    114:                              Clean up
    115:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
    116:   STDestroy(&st);
    117:   MatDestroy(&A);
    118:   MatDestroy(&P);
    119:   VecDestroy(&v);
    120:   VecDestroy(&w);
    121:   SlepcFinalize();
    122:   return ierr;
    123: }

    125: /*TEST

    127:    test:
    128:       suffix: 1
    129:       args: -st_matmode {{copy inplace}}
    130:       requires: !single

    132:    test:
    133:       suffix: 2
    134:       args: -st_matmode shell

    136: TEST*/