int main(int argc,char *argv[])
{
PetscErrorCode ierr;
Mat A,S = NULL,Sexplicit = NULL;
IS is0,is1;
ierr = PetscInitialize(&argc,&argv,0,help);if (ierr) return ierr;
/* Test the Schur complement one way */
ierr = Create(PETSC_COMM_WORLD,&A,&is0,&is1);CHKERRQ(ierr);
ierr = MatView(A,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);
ierr = ISView(is0,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);
ierr = ISView(is1,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);
ierr = MatGetSchurComplement(A,is0,is0,is1,is1,MAT_INITIAL_MATRIX,&S,MAT_SCHUR_COMPLEMENT_AINV_DIAG,MAT_IGNORE_MATRIX,NULL);CHKERRQ(ierr);
ierr = MatComputeExplicitOperator(S,&Sexplicit);CHKERRQ(ierr);
ierr = PetscPrintf(PETSC_COMM_WORLD,"\nExplicit Schur complement of (0,0) in (1,1)\n");CHKERRQ(ierr);
ierr = MatView(Sexplicit,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);
ierr = Destroy(&A,&is0,&is1);CHKERRQ(ierr);
ierr = MatDestroy(&S);CHKERRQ(ierr);
ierr = MatDestroy(&Sexplicit);CHKERRQ(ierr);
/* And the other */
ierr = Create(PETSC_COMM_WORLD,&A,&is0,&is1);CHKERRQ(ierr);
ierr = MatGetSchurComplement(A,is1,is1,is0,is0,MAT_INITIAL_MATRIX,&S,MAT_SCHUR_COMPLEMENT_AINV_DIAG,MAT_IGNORE_MATRIX,NULL);CHKERRQ(ierr);
ierr = MatComputeExplicitOperator(S,&Sexplicit);CHKERRQ(ierr);
ierr = PetscPrintf(PETSC_COMM_WORLD,"\nExplicit Schur complement of (1,1) in (0,0)\n");CHKERRQ(ierr);
ierr = MatView(Sexplicit,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);
ierr = Destroy(&A,&is0,&is1);CHKERRQ(ierr);
ierr = MatDestroy(&S);CHKERRQ(ierr);
ierr = MatDestroy(&Sexplicit);CHKERRQ(ierr);
/* This time just the preconditioning matrix. */
ierr = Create(PETSC_COMM_WORLD,&A,&is0,&is1);CHKERRQ(ierr);
ierr = MatGetSchurComplement(A,is0,is0,is1,is1,MAT_IGNORE_MATRIX,NULL,MAT_SCHUR_COMPLEMENT_AINV_DIAG,MAT_INITIAL_MATRIX,&S);CHKERRQ(ierr);
ierr = PetscPrintf(PETSC_COMM_WORLD,"\nPreconditioning Schur complement of (0,0) in (1,1)\n");CHKERRQ(ierr);
ierr = MatView(S,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);
/* Modify and refresh */
ierr = MatShift(A,1.);CHKERRQ(ierr);
ierr = MatGetSchurComplement(A,is0,is0,is1,is1,MAT_IGNORE_MATRIX,NULL,MAT_SCHUR_COMPLEMENT_AINV_DIAG,MAT_REUSE_MATRIX,&S);CHKERRQ(ierr);
ierr = PetscPrintf(PETSC_COMM_WORLD,"\nAfter update\n");CHKERRQ(ierr);
ierr = MatView(S,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);
ierr = Destroy(&A,&is0,&is1);CHKERRQ(ierr);
ierr = MatDestroy(&S);CHKERRQ(ierr);
ierr = PetscFinalize();
return ierr;
}
int main(int argc,char *argv[])
{
PetscErrorCode ierr;
Mat A,S,Sexplicit;
IS is0,is1;
ierr = PetscInitialize(&argc,&argv,0,help);CHKERRQ(ierr);
/* Test the Schur complement one way */
ierr = Create(PETSC_COMM_WORLD,&A,&is0,&is1);CHKERRQ(ierr);
ierr = MatView(A,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);
ierr = ISView(is0,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);
ierr = ISView(is1,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);
ierr = MatGetSchurComplement(A,is0,is0,is1,is1,MAT_INITIAL_MATRIX,&S,MAT_IGNORE_MATRIX,PETSC_NULL);CHKERRQ(ierr);
ierr = MatComputeExplicitOperator(S,&Sexplicit);CHKERRQ(ierr);
ierr = PetscPrintf(PETSC_COMM_WORLD,"\nExplicit Schur complement of (0,0) in (1,1)\n");CHKERRQ(ierr);
ierr = MatView(Sexplicit,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);
ierr = Destroy(A,is0,is1);CHKERRQ(ierr);
ierr = MatDestroy(S);CHKERRQ(ierr);
ierr = MatDestroy(Sexplicit);CHKERRQ(ierr);
/* And the other */
ierr = Create(PETSC_COMM_WORLD,&A,&is0,&is1);CHKERRQ(ierr);
ierr = MatGetSchurComplement(A,is1,is1,is0,is0,MAT_INITIAL_MATRIX,&S,MAT_IGNORE_MATRIX,PETSC_NULL);CHKERRQ(ierr);
ierr = MatComputeExplicitOperator(S,&Sexplicit);CHKERRQ(ierr);
ierr = PetscPrintf(PETSC_COMM_WORLD,"\nExplicit Schur complement of (1,1) in (0,0)\n");CHKERRQ(ierr);
ierr = MatView(Sexplicit,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);
ierr = Destroy(A,is0,is1);CHKERRQ(ierr);
ierr = MatDestroy(S);CHKERRQ(ierr);
ierr = MatDestroy(Sexplicit);CHKERRQ(ierr);
/* This time just the preconditioner */
ierr = Create(PETSC_COMM_WORLD,&A,&is0,&is1);CHKERRQ(ierr);
ierr = MatGetSchurComplement(A,is0,is0,is1,is1,MAT_IGNORE_MATRIX,PETSC_NULL,MAT_INITIAL_MATRIX,&S);CHKERRQ(ierr);
ierr = PetscPrintf(PETSC_COMM_WORLD,"\nPreconditioning Schur complement of (0,0) in (1,1)\n");CHKERRQ(ierr);
ierr = MatView(S,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);
ierr = Destroy(A,is0,is1);CHKERRQ(ierr);
ierr = MatDestroy(S);CHKERRQ(ierr);
ierr = PetscFinalize();CHKERRQ(ierr);
return 0;
}