Actual source code: ex17.c

  1: static char help[] = "Tests the use of MatSolveTranspose().\n\n";

  3: #include <petscmat.h>

  5: int main(int argc, char **args)
  6: {
  7:   Mat           C, A;
  8:   PetscInt      i, j, m = 5, n = 5, Ii, J;
  9:   PetscScalar   v, five = 5.0, one = 1.0;
 10:   IS            isrow, row, col;
 11:   Vec           x, u, b;
 12:   PetscReal     norm;
 13:   MatFactorInfo info;

 15:   PetscFunctionBeginUser;
 16:   PetscCall(PetscInitialize(&argc, &args, NULL, help));
 17:   PetscCall(PetscOptionsGetInt(NULL, NULL, "-m", &m, NULL));
 18:   PetscCall(PetscOptionsGetInt(NULL, NULL, "-n", &n, NULL));

 20:   PetscCall(MatCreateSeqAIJ(PETSC_COMM_SELF, m * n, m * n, 5, NULL, &C));
 21:   PetscCall(MatSetUp(C));

 23:   /* create the matrix for the five point stencil, YET AGAIN*/
 24:   for (i = 0; i < m; i++) {
 25:     for (j = 0; j < n; j++) {
 26:       v  = -1.0;
 27:       Ii = j + n * i;
 28:       if (i > 0) {
 29:         J = Ii - n;
 30:         PetscCall(MatSetValues(C, 1, &Ii, 1, &J, &v, INSERT_VALUES));
 31:       }
 32:       if (i < m - 1) {
 33:         J = Ii + n;
 34:         PetscCall(MatSetValues(C, 1, &Ii, 1, &J, &v, INSERT_VALUES));
 35:       }
 36:       if (j > 0) {
 37:         J = Ii - 1;
 38:         PetscCall(MatSetValues(C, 1, &Ii, 1, &J, &v, INSERT_VALUES));
 39:       }
 40:       if (j < n - 1) {
 41:         J = Ii + 1;
 42:         PetscCall(MatSetValues(C, 1, &Ii, 1, &J, &v, INSERT_VALUES));
 43:       }
 44:       v = 4.0;
 45:       PetscCall(MatSetValues(C, 1, &Ii, 1, &Ii, &v, INSERT_VALUES));
 46:     }
 47:   }
 48:   PetscCall(MatAssemblyBegin(C, MAT_FINAL_ASSEMBLY));
 49:   PetscCall(MatAssemblyEnd(C, MAT_FINAL_ASSEMBLY));

 51:   PetscCall(ISCreateStride(PETSC_COMM_SELF, (m * n) / 2, 0, 2, &isrow));
 52:   PetscCall(MatZeroRowsIS(C, isrow, five, 0, 0));

 54:   PetscCall(VecCreateSeq(PETSC_COMM_SELF, m * n, &u));
 55:   PetscCall(VecDuplicate(u, &x));
 56:   PetscCall(VecDuplicate(u, &b));
 57:   PetscCall(VecSet(u, one));

 59:   PetscCall(MatMultTranspose(C, u, b));

 61:   /* Set default ordering to be Quotient Minimum Degree; also read
 62:      orderings from the options database */
 63:   PetscCall(MatGetOrdering(C, MATORDERINGQMD, &row, &col));

 65:   PetscCall(MatFactorInfoInitialize(&info));
 66:   PetscCall(MatGetFactor(C, MATSOLVERPETSC, MAT_FACTOR_LU, &A));
 67:   PetscCall(MatLUFactorSymbolic(A, C, row, col, &info));
 68:   PetscCall(MatLUFactorNumeric(A, C, &info));
 69:   PetscCall(MatSolveTranspose(A, b, x));

 71:   PetscCall(ISView(row, PETSC_VIEWER_STDOUT_SELF));
 72:   PetscCall(VecAXPY(x, -1.0, u));
 73:   PetscCall(VecNorm(x, NORM_2, &norm));
 74:   PetscCall(PetscPrintf(PETSC_COMM_SELF, "Norm of error %g\n", (double)norm));

 76:   PetscCall(ISDestroy(&row));
 77:   PetscCall(ISDestroy(&col));
 78:   PetscCall(ISDestroy(&isrow));
 79:   PetscCall(VecDestroy(&u));
 80:   PetscCall(VecDestroy(&x));
 81:   PetscCall(VecDestroy(&b));
 82:   PetscCall(MatDestroy(&C));
 83:   PetscCall(MatDestroy(&A));
 84:   PetscCall(PetscFinalize());
 85:   return 0;
 86: }

 88: /*TEST

 90:    test:

 92: TEST*/