Actual source code: ex7.c


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

  6: #include <petscmat.h>

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

 20:   PetscInitialize(&argc, &args, (char *)0, help);

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

 30:   PetscOptionsEnd();

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

 67:   MatFactorInfoInitialize(&luinfo);

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

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

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

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

 86:   VecView(b, PETSC_VIEWER_STDOUT_SELF);
 87:   VecView(x, PETSC_VIEWER_STDOUT_SELF);

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

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

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

106:   PetscFinalize();
107:   return 0;
108: }

110: /*TEST

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

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

121: TEST*/