Date: 2026-03-09T09:12:16+00:00

Actual source code: test8.c

      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 ST with two matrices and split preconditioner.\n\n";

     13: #include <slepcst.h>

     15: int main(int argc,char **argv)
     16: {
     17:   Mat            A,B,Pa,Pb,Pmat,mat[2];
     18:   ST             st;
     19:   KSP            ksp;
     20:   PC             pc;
     21:   Vec            v,w;
     22:   STType         type;
     23:   PetscScalar    sigma;
     24:   PetscInt       n=10,i,Istart,Iend;

     26:   PetscFunctionBeginUser;
     27:   PetscCall(SlepcInitialize(&argc,&argv,NULL,help));
     28:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL));
     29:   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"\n1-D Laplacian plus diagonal, n=%" PetscInt_FMT "\n\n",n));

     31:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     32:      Compute the operator matrices (1-D Laplacian and diagonal)
     33:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     35:   PetscCall(MatCreate(PETSC_COMM_WORLD,&A));
     36:   PetscCall(MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,n,n));
     37:   PetscCall(MatSetFromOptions(A));

     39:   PetscCall(MatCreate(PETSC_COMM_WORLD,&B));
     40:   PetscCall(MatSetSizes(B,PETSC_DECIDE,PETSC_DECIDE,n,n));
     41:   PetscCall(MatSetFromOptions(B));

     43:   PetscCall(MatGetOwnershipRange(A,&Istart,&Iend));
     44:   for (i=Istart;i<Iend;i++) {
     45:     PetscCall(MatSetValue(A,i,i,2.0,INSERT_VALUES));
     46:     if (i>0) {
     47:       PetscCall(MatSetValue(A,i,i-1,-1.0,INSERT_VALUES));
     48:       PetscCall(MatSetValue(B,i,i,(PetscScalar)i,INSERT_VALUES));
     49:     } else PetscCall(MatSetValue(B,i,i,-1.0,INSERT_VALUES));
     50:     if (i<n-1) PetscCall(MatSetValue(A,i,i+1,-1.0,INSERT_VALUES));
     51:   }
     52:   PetscCall(MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY));
     53:   PetscCall(MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY));
     54:   PetscCall(MatAssemblyBegin(B,MAT_FINAL_ASSEMBLY));
     55:   PetscCall(MatAssemblyEnd(B,MAT_FINAL_ASSEMBLY));
     56:   PetscCall(MatCreateVecs(A,&v,&w));
     57:   PetscCall(VecSet(v,1.0));

     59:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     60:      Compute the split preconditioner matrices (two diagonals)
     61:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     63:   PetscCall(MatCreate(PETSC_COMM_WORLD,&Pa));
     64:   PetscCall(MatSetSizes(Pa,PETSC_DECIDE,PETSC_DECIDE,n,n));
     65:   PetscCall(MatSetFromOptions(Pa));

     67:   PetscCall(MatCreate(PETSC_COMM_WORLD,&Pb));
     68:   PetscCall(MatSetSizes(Pb,PETSC_DECIDE,PETSC_DECIDE,n,n));
     69:   PetscCall(MatSetFromOptions(Pb));

     71:   PetscCall(MatGetOwnershipRange(Pa,&Istart,&Iend));
     72:   for (i=Istart;i<Iend;i++) {
     73:     PetscCall(MatSetValue(Pa,i,i,2.0,INSERT_VALUES));
     74:     if (i>0) PetscCall(MatSetValue(Pb,i,i,(PetscScalar)i,INSERT_VALUES));
     75:     else PetscCall(MatSetValue(Pb,i,i,-1.0,INSERT_VALUES));
     76:   }
     77:   PetscCall(MatAssemblyBegin(Pa,MAT_FINAL_ASSEMBLY));
     78:   PetscCall(MatAssemblyEnd(Pa,MAT_FINAL_ASSEMBLY));
     79:   PetscCall(MatAssemblyBegin(Pb,MAT_FINAL_ASSEMBLY));
     80:   PetscCall(MatAssemblyEnd(Pb,MAT_FINAL_ASSEMBLY));

     82:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     83:                 Create the spectral transformation object
     84:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     86:   PetscCall(STCreate(PETSC_COMM_WORLD,&st));
     87:   mat[0] = A;
     88:   mat[1] = B;
     89:   PetscCall(STSetMatrices(st,2,mat));
     90:   mat[0] = Pa;
     91:   mat[1] = Pb;
     92:   PetscCall(STSetSplitPreconditioner(st,2,mat,SAME_NONZERO_PATTERN));
     93:   PetscCall(STSetTransform(st,PETSC_TRUE));
     94:   PetscCall(STSetFromOptions(st));
     95:   PetscCall(STCayleySetAntishift(st,-0.2));   /* only relevant for cayley */

     97:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     98:                Form the preconditioner matrix and print it
     99:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    101:   PetscCall(STGetKSP(st,&ksp));
    102:   PetscCall(KSPGetPC(ksp,&pc));
    103:   PetscCall(STGetOperator(st,NULL));
    104:   PetscCall(PCGetOperators(pc,NULL,&Pmat));
    105:   PetscCall(MatView(Pmat,NULL));

    107:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    108:                    Apply the operator
    109:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    111:   /* sigma=0.0 */
    112:   PetscCall(STSetUp(st));
    113:   PetscCall(STGetType(st,&type));
    114:   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"ST type %s\n",type));
    115:   PetscCall(STApply(st,v,w));
    116:   PetscCall(VecView(w,NULL));

    118:   /* sigma=0.1 */
    119:   sigma = 0.1;
    120:   PetscCall(STSetShift(st,sigma));
    121:   PetscCall(STGetShift(st,&sigma));
    122:   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"With shift=%g\n",(double)PetscRealPart(sigma)));
    123:   PetscCall(STGetOperator(st,NULL));
    124:   PetscCall(PCGetOperators(pc,NULL,&Pmat));
    125:   PetscCall(MatView(Pmat,NULL));
    126:   PetscCall(STApply(st,v,w));
    127:   PetscCall(VecView(w,NULL));

    129:   PetscCall(STDestroy(&st));
    130:   PetscCall(MatDestroy(&A));
    131:   PetscCall(MatDestroy(&B));
    132:   PetscCall(MatDestroy(&Pa));
    133:   PetscCall(MatDestroy(&Pb));
    134:   PetscCall(VecDestroy(&v));
    135:   PetscCall(VecDestroy(&w));
    136:   PetscCall(SlepcFinalize());
    137:   return 0;
    138: }

    140: /*TEST

    142:    test:
    143:       suffix: 1
    144:       args: -st_type {{cayley shift sinvert}separate output}
    145:       requires: !single

    147: TEST*/