Actual source code: ex4.c

  1: static char help[] = "Demonstrates the use of fast Richardson for SOR. And tests\n\
  2: the MatSOR() routines.\n\n";

  4: #include <petscpc.h>

  6: int main(int argc, char **args)
  7: {
  8:   Mat         mat;
  9:   Vec         b, u;
 10:   PC          pc;
 11:   PetscInt    n = 5, i, col[3];
 12:   PetscScalar value[3];

 14:   PetscFunctionBeginUser;
 15:   PetscCall(PetscInitialize(&argc, &args, (char *)0, help));
 16:   /* Create vectors */
 17:   PetscCall(VecCreateSeq(PETSC_COMM_SELF, n, &b));
 18:   PetscCall(VecCreateSeq(PETSC_COMM_SELF, n, &u));

 20:   /* Create and assemble matrix */
 21:   PetscCall(MatCreateSeqDense(PETSC_COMM_SELF, n, n, NULL, &mat));
 22:   value[0] = -1.0;
 23:   value[1] = 2.0;
 24:   value[2] = -1.0;
 25:   for (i = 1; i < n - 1; i++) {
 26:     col[0] = i - 1;
 27:     col[1] = i;
 28:     col[2] = i + 1;
 29:     PetscCall(MatSetValues(mat, 1, &i, 3, col, value, INSERT_VALUES));
 30:   }
 31:   i      = n - 1;
 32:   col[0] = n - 2;
 33:   col[1] = n - 1;
 34:   PetscCall(MatSetValues(mat, 1, &i, 2, col, value, INSERT_VALUES));
 35:   i        = 0;
 36:   col[0]   = 0;
 37:   col[1]   = 1;
 38:   value[0] = 2.0;
 39:   value[1] = -1.0;
 40:   PetscCall(MatSetValues(mat, 1, &i, 2, col, value, INSERT_VALUES));
 41:   PetscCall(MatAssemblyBegin(mat, MAT_FINAL_ASSEMBLY));
 42:   PetscCall(MatAssemblyEnd(mat, MAT_FINAL_ASSEMBLY));

 44:   /* Create PC context and set up data structures */
 45:   PetscCall(PCCreate(PETSC_COMM_WORLD, &pc));
 46:   PetscCall(PCSetType(pc, PCSOR));
 47:   PetscCall(PCSetFromOptions(pc));
 48:   PetscCall(PCSetOperators(pc, mat, mat));
 49:   PetscCall(PCSetUp(pc));

 51:   value[0] = 1.0;
 52:   for (i = 0; i < n; i++) {
 53:     PetscCall(VecSet(u, 0.0));
 54:     PetscCall(VecSetValues(u, 1, &i, value, INSERT_VALUES));
 55:     PetscCall(VecAssemblyBegin(u));
 56:     PetscCall(VecAssemblyEnd(u));
 57:     PetscCall(PCApply(pc, u, b));
 58:     PetscCall(VecView(b, PETSC_VIEWER_STDOUT_SELF));
 59:   }

 61:   /* Free data structures */
 62:   PetscCall(MatDestroy(&mat));
 63:   PetscCall(PCDestroy(&pc));
 64:   PetscCall(VecDestroy(&u));
 65:   PetscCall(VecDestroy(&b));
 66:   PetscCall(PetscFinalize());
 67:   return 0;
 68: }

 70: /*TEST

 72:    test:

 74: TEST*/