Actual source code: ex7.c

  1: static char help[] = "Tests matrix factorization.  Note that most users should\n\
  2: employ the KSP  interface to the linear solvers instead of using the factorization\n\
  3: routines directly.\n\n";

  5: #include <petscmat.h>

  7: int main(int argc, char **args)
  8: {
  9:   Mat           C, LU;
 10:   MatInfo       info;
 11:   PetscInt      i, j, m, n, Ii, J;
 12:   PetscScalar   v, one = 1.0;
 13:   IS            perm, iperm;
 14:   Vec           x, u, b;
 15:   PetscReal     norm, fill;
 16:   MatFactorInfo luinfo;

 18:   PetscFunctionBeginUser;
 19:   PetscCall(PetscInitialize(&argc, &args, NULL, help));

 21:   PetscOptionsBegin(PETSC_COMM_WORLD, NULL, "Mat test ex7 options", "Mat");
 22:   m    = 3;
 23:   n    = 3;
 24:   fill = 2.0;
 25:   PetscCall(PetscOptionsInt("-m", "Number of rows in grid", NULL, m, &m, NULL));
 26:   PetscCall(PetscOptionsInt("-n", "Number of columns in grid", NULL, n, &n, NULL));
 27:   PetscCall(PetscOptionsReal("-fill", "Expected fill ratio for factorization", NULL, fill, &fill, NULL));

 29:   PetscOptionsEnd();

 31:   /* Create the matrix for the five point stencil, YET AGAIN */
 32:   PetscCall(MatCreate(PETSC_COMM_SELF, &C));
 33:   PetscCall(MatSetSizes(C, PETSC_DECIDE, PETSC_DECIDE, m * n, m * n));
 34:   PetscCall(MatSetFromOptions(C));
 35:   PetscCall(MatSetUp(C));
 36:   for (i = 0; i < m; i++) {
 37:     for (j = 0; j < n; j++) {
 38:       v  = -1.0;
 39:       Ii = j + n * i;
 40:       if (i > 0) {
 41:         J = Ii - n;
 42:         PetscCall(MatSetValues(C, 1, &Ii, 1, &J, &v, INSERT_VALUES));
 43:       }
 44:       if (i < m - 1) {
 45:         J = Ii + n;
 46:         PetscCall(MatSetValues(C, 1, &Ii, 1, &J, &v, INSERT_VALUES));
 47:       }
 48:       if (j > 0) {
 49:         J = Ii - 1;
 50:         PetscCall(MatSetValues(C, 1, &Ii, 1, &J, &v, INSERT_VALUES));
 51:       }
 52:       if (j < n - 1) {
 53:         J = Ii + 1;
 54:         PetscCall(MatSetValues(C, 1, &Ii, 1, &J, &v, INSERT_VALUES));
 55:       }
 56:       v = 4.0;
 57:       PetscCall(MatSetValues(C, 1, &Ii, 1, &Ii, &v, INSERT_VALUES));
 58:     }
 59:   }
 60:   PetscCall(MatAssemblyBegin(C, MAT_FINAL_ASSEMBLY));
 61:   PetscCall(MatAssemblyEnd(C, MAT_FINAL_ASSEMBLY));
 62:   PetscCall(MatGetOrdering(C, MATORDERINGRCM, &perm, &iperm));
 63:   PetscCall(MatView(C, PETSC_VIEWER_STDOUT_WORLD));
 64:   PetscCall(ISView(perm, PETSC_VIEWER_STDOUT_SELF));

 66:   PetscCall(MatFactorInfoInitialize(&luinfo));

 68:   luinfo.fill          = fill;
 69:   luinfo.dtcol         = 0.0;
 70:   luinfo.zeropivot     = 1.e-14;
 71:   luinfo.pivotinblocks = 1.0;

 73:   PetscCall(MatGetFactor(C, MATSOLVERPETSC, MAT_FACTOR_LU, &LU));
 74:   PetscCall(MatLUFactorSymbolic(LU, C, perm, iperm, &luinfo));
 75:   PetscCall(MatLUFactorNumeric(LU, C, &luinfo));

 77:   PetscCall(VecCreateSeq(PETSC_COMM_SELF, m * n, &u));
 78:   PetscCall(VecSet(u, one));
 79:   PetscCall(VecDuplicate(u, &x));
 80:   PetscCall(VecDuplicate(u, &b));

 82:   PetscCall(MatMult(C, u, b));
 83:   PetscCall(MatSolve(LU, b, x));

 85:   PetscCall(VecView(b, PETSC_VIEWER_STDOUT_SELF));
 86:   PetscCall(VecView(x, PETSC_VIEWER_STDOUT_SELF));

 88:   PetscCall(VecAXPY(x, -1.0, u));
 89:   PetscCall(VecNorm(x, NORM_2, &norm));
 90:   PetscCall(PetscPrintf(PETSC_COMM_SELF, "Norm of error %g\n", (double)norm));

 92:   PetscCall(MatGetInfo(C, MAT_LOCAL, &info));
 93:   PetscCall(PetscPrintf(PETSC_COMM_SELF, "original matrix nonzeros = %" PetscInt_FMT "\n", (PetscInt)info.nz_used));
 94:   PetscCall(MatGetInfo(LU, MAT_LOCAL, &info));
 95:   PetscCall(PetscPrintf(PETSC_COMM_SELF, "factored matrix nonzeros = %" PetscInt_FMT "\n", (PetscInt)info.nz_used));

 97:   PetscCall(VecDestroy(&u));
 98:   PetscCall(VecDestroy(&b));
 99:   PetscCall(VecDestroy(&x));
100:   PetscCall(ISDestroy(&perm));
101:   PetscCall(ISDestroy(&iperm));
102:   PetscCall(MatDestroy(&C));
103:   PetscCall(MatDestroy(&LU));

105:   PetscCall(PetscFinalize());
106:   return 0;
107: }

109: /*TEST

111:    test:
112:       suffix: 1
113:       filter: grep -v " MPI process"

115:    test:
116:       suffix: 2
117:       args: -m 1 -n 1 -fill 0.49
118:       filter: grep -v " MPI process"

120: TEST*/