You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
96 lines
2.8 KiB
C
96 lines
2.8 KiB
C
static char help[] = "Solves a tridiagonal linear system.\n\n";
|
|
|
|
#include <petscksp.h>
|
|
|
|
int main(int argc, char **args)
|
|
{
|
|
Vec x, b, u; /* approx solution, RHS, exact solution */
|
|
Mat A; /* linear system matrix */
|
|
KSP ksp; /* linear solver context */
|
|
PC pc; /* preconditioner context */
|
|
PetscReal norm, tol = 1000. * PETSC_MACHINE_EPSILON; /* norm of solution error */
|
|
PetscInt i, n = 10, col[3], its, rstart, rend, nlocal;
|
|
PetscScalar one = 1.0, value[3];
|
|
|
|
PetscFunctionBeginUser;
|
|
PetscCall(PetscInitialize(&argc, &args, (char *)0, help));
|
|
PetscCall(PetscOptionsGetInt(NULL, NULL, "-n", &n, NULL));
|
|
|
|
PetscCall(VecCreate(PETSC_COMM_WORLD, &x));
|
|
PetscCall(VecSetSizes(x, PETSC_DECIDE, n));
|
|
PetscCall(VecSetFromOptions(x));
|
|
PetscCall(VecDuplicate(x, &b));
|
|
PetscCall(VecDuplicate(x, &u));
|
|
|
|
PetscCall(VecGetOwnershipRange(x, &rstart, &rend));
|
|
PetscCall(VecGetLocalSize(x, &nlocal));
|
|
|
|
PetscCall(MatCreate(PETSC_COMM_WORLD, &A));
|
|
PetscCall(MatSetSizes(A, nlocal, nlocal, n, n));
|
|
PetscCall(MatSetFromOptions(A));
|
|
PetscCall(MatSetUp(A));
|
|
|
|
if (!rstart) {
|
|
rstart = 1;
|
|
i = 0;
|
|
col[0] = 0;
|
|
col[1] = 1;
|
|
value[0] = 2.0;
|
|
value[1] = -1.0;
|
|
PetscCall(MatSetValues(A, 1, &i, 2, col, value, INSERT_VALUES));
|
|
}
|
|
if (rend == n) {
|
|
rend = n - 1;
|
|
i = n - 1;
|
|
col[0] = n - 2;
|
|
col[1] = n - 1;
|
|
value[0] = -1.0;
|
|
value[1] = 2.0;
|
|
PetscCall(MatSetValues(A, 1, &i, 2, col, value, INSERT_VALUES));
|
|
}
|
|
|
|
value[0] = -1.0;
|
|
value[1] = 2.0;
|
|
value[2] = -1.0;
|
|
for (i = rstart; i < rend; i++) {
|
|
col[0] = i - 1;
|
|
col[1] = i;
|
|
col[2] = i + 1;
|
|
PetscCall(MatSetValues(A, 1, &i, 3, col, value, INSERT_VALUES));
|
|
}
|
|
|
|
PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
|
|
PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
|
|
|
|
PetscCall(VecSet(u, one));
|
|
PetscCall(MatMult(A, u, b));
|
|
|
|
PetscCall(KSPCreate(PETSC_COMM_WORLD, &ksp));
|
|
|
|
PetscCall(KSPSetOperators(ksp, A, A));
|
|
|
|
PetscCall(KSPGetPC(ksp, &pc));
|
|
PetscCall(PCSetType(pc, PCJACOBI));
|
|
PetscCall(KSPSetTolerances(ksp, 1.e-7, PETSC_DEFAULT, PETSC_DEFAULT, PETSC_DEFAULT));
|
|
|
|
PetscCall(KSPSetFromOptions(ksp));
|
|
|
|
PetscCall(KSPSolve(ksp, b, x));
|
|
|
|
PetscCall(KSPView(ksp, PETSC_VIEWER_STDOUT_WORLD));
|
|
|
|
PetscCall(VecAXPY(x, -1.0, u));
|
|
PetscCall(VecNorm(x, NORM_2, &norm));
|
|
PetscCall(KSPGetIterationNumber(ksp, &its));
|
|
if (norm > tol) PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Norm of error %g, Iterations %" PetscInt_FMT "\n", (double)norm, its));
|
|
|
|
PetscCall(VecDestroy(&x));
|
|
PetscCall(VecDestroy(&u));
|
|
PetscCall(VecDestroy(&b));
|
|
PetscCall(MatDestroy(&A));
|
|
PetscCall(KSPDestroy(&ksp));
|
|
|
|
PetscCall(PetscFinalize());
|
|
return 0;
|
|
}
|