Actual source code: ex4.c


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

  5: #include <petscpc.h>

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

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

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

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

 52:   value[0] = 1.0;
 53:   for (i = 0; i < n; i++) {
 54:     PetscCall(VecSet(u, 0.0));
 55:     PetscCall(VecSetValues(u, 1, &i, value, INSERT_VALUES));
 56:     PetscCall(VecAssemblyBegin(u));
 57:     PetscCall(VecAssemblyEnd(u));
 58:     PetscCall(PCApply(pc, u, b));
 59:     PetscCall(VecView(b, PETSC_VIEWER_STDOUT_SELF));
 60:   }

 62:   /* Free data structures */
 63:   PetscCall(MatDestroy(&mat));
 64:   PetscCall(PCDestroy(&pc));
 65:   PetscCall(VecDestroy(&u));
 66:   PetscCall(VecDestroy(&b));
 67:   PetscCall(PetscFinalize());
 68:   return 0;
 69: }

 71: /*TEST

 73:    test:

 75: TEST*/