int main(int argc,char **args)
{
KSP ksp;
PC pc;
Mat A;
Vec u, x, b;
PetscReal error;
PetscMPIInt rank, size, sized;
PetscInt M = 8, N = 8, m, n, rstart, rend, r;
PetscBool userSubdomains = PETSC_FALSE;
PetscErrorCode ierr;
ierr = PetscInitialize(&argc, &args, NULL,help);if (ierr) return ierr;
ierr = PetscOptionsGetInt(NULL,NULL, "-M", &M, NULL);CHKERRQ(ierr);
ierr = PetscOptionsGetInt(NULL,NULL, "-N", &N, NULL);CHKERRQ(ierr);
ierr = PetscOptionsGetBool(NULL,NULL, "-user_subdomains", &userSubdomains, NULL);CHKERRQ(ierr);
/* Do parallel decomposition */
ierr = MPI_Comm_rank(PETSC_COMM_WORLD, &rank);CHKERRQ(ierr);
ierr = MPI_Comm_size(PETSC_COMM_WORLD, &size);CHKERRQ(ierr);
sized = (PetscMPIInt) PetscSqrtReal((PetscReal) size);
if (PetscSqr(sized) != size) SETERRQ1(PETSC_COMM_WORLD, PETSC_ERR_ARG_WRONG, "This test may only be run on a nubmer of processes which is a perfect square, not %d", (int) size);
if (M % sized) SETERRQ2(PETSC_COMM_WORLD, PETSC_ERR_ARG_WRONG, "The number of x-vertices %D does not divide the number of x-processes %d", M, (int) sized);
if (N % sized) SETERRQ2(PETSC_COMM_WORLD, PETSC_ERR_ARG_WRONG, "The number of y-vertices %D does not divide the number of y-processes %d", N, (int) sized);
/* Assemble the matrix for the five point stencil, YET AGAIN
Every other process will be empty */
ierr = MatCreate(PETSC_COMM_WORLD, &A);CHKERRQ(ierr);
m = (sized > 1) ? (rank % 2) ? 0 : 2*M/sized : M;
n = N/sized;
ierr = MatSetSizes(A, m*n, m*n, M*N, M*N);CHKERRQ(ierr);
ierr = MatSetFromOptions(A);CHKERRQ(ierr);
ierr = MatSetUp(A);CHKERRQ(ierr);
ierr = MatGetOwnershipRange(A, &rstart, &rend);CHKERRQ(ierr);
for (r = rstart; r < rend; ++r) {
const PetscScalar diag = 4.0, offdiag = -1.0;
const PetscInt i = r/N;
const PetscInt j = r - i*N;
PetscInt c;
if (i > 0) {c = r - n; ierr = MatSetValues(A, 1, &r, 1, &c, &offdiag, INSERT_VALUES);CHKERRQ(ierr);}
if (i < M-1) {c = r + n; ierr = MatSetValues(A, 1, &r, 1, &c, &offdiag, INSERT_VALUES);CHKERRQ(ierr);}
if (j > 0) {c = r - 1; ierr = MatSetValues(A, 1, &r, 1, &c, &offdiag, INSERT_VALUES);CHKERRQ(ierr);}
if (j < N-1) {c = r + 1; ierr = MatSetValues(A, 1, &r, 1, &c, &offdiag, INSERT_VALUES);CHKERRQ(ierr);}
ierr = MatSetValues(A, 1, &r, 1, &r, &diag, INSERT_VALUES);CHKERRQ(ierr);
}
ierr = MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
ierr = MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
/* Setup Solve */
ierr = VecCreate(PETSC_COMM_WORLD, &b);CHKERRQ(ierr);
ierr = VecSetSizes(b, m*n, PETSC_DETERMINE);CHKERRQ(ierr);
ierr = VecSetFromOptions(b);CHKERRQ(ierr);
ierr = VecDuplicate(b, &u);CHKERRQ(ierr);
ierr = VecDuplicate(b, &x);CHKERRQ(ierr);
ierr = VecSet(u, 1.0);CHKERRQ(ierr);
ierr = MatMult(A, u, b);CHKERRQ(ierr);
ierr = KSPCreate(PETSC_COMM_WORLD, &ksp);CHKERRQ(ierr);
ierr = KSPSetOperators(ksp, A, A);CHKERRQ(ierr);
ierr = KSPGetPC(ksp, &pc);CHKERRQ(ierr);
ierr = PCSetType(pc, PCASM);CHKERRQ(ierr);
/* Setup ASM by hand */
if (userSubdomains) {
IS is;
PetscInt *rows;
/* Use no overlap for now */
ierr = PetscMalloc1(rend-rstart, &rows);CHKERRQ(ierr);
for (r = rstart; r < rend; ++r) rows[r-rstart] = r;
ierr = ISCreateGeneral(PETSC_COMM_SELF, rend-rstart, rows, PETSC_OWN_POINTER, &is);CHKERRQ(ierr);
ierr = PCASMSetLocalSubdomains(pc, 1, &is, &is);CHKERRQ(ierr);
ierr = ISDestroy(&is);CHKERRQ(ierr);
}
ierr = KSPSetFromOptions(ksp);CHKERRQ(ierr);
/* Solve and Compare */
ierr = KSPSolve(ksp, b, x);CHKERRQ(ierr);
ierr = VecAXPY(x, -1.0, u);CHKERRQ(ierr);
ierr = VecNorm(x, NORM_INFINITY, &error);CHKERRQ(ierr);
ierr = PetscPrintf(PETSC_COMM_WORLD, "Infinity norm of the error: %g\n", (double) error);CHKERRQ(ierr);
/* Cleanup */
ierr = KSPDestroy(&ksp);CHKERRQ(ierr);
ierr = MatDestroy(&A);CHKERRQ(ierr);
ierr = VecDestroy(&u);CHKERRQ(ierr);
ierr = VecDestroy(&x);CHKERRQ(ierr);
ierr = VecDestroy(&b);CHKERRQ(ierr);
ierr = PetscFinalize();
return ierr;
}
void PETSC_STDCALL pcasmsetlocalsubdomains_(PC *pc,PetscInt *n,IS *is,IS *is_local, PetscErrorCode *ierr)
{
CHKFORTRANNULLOBJECT(is);
CHKFORTRANNULLOBJECT(is_local);
*ierr = PCASMSetLocalSubdomains(*pc,*n,is,is_local);
}
