Actual source code: ex247.c
2: static char help[] = "Tests MATCENTERING matrix type.\n\n";
4: #include <petscmat.h>
6: int main(int argc, char **argv)
7: {
8: PetscInt n;
9: Mat C;
10: Vec x, y;
11: PetscReal norm;
12: PetscMPIInt size;
14: PetscFunctionBeginUser;
15: PetscCall(PetscInitialize(&argc, &argv, (char *)0, help));
16: PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
18: /* Create a parallel vector with 10*size total entries, and fill it with 1s. */
19: n = 10 * size;
20: PetscCall(VecCreate(PETSC_COMM_WORLD, &x));
21: PetscCall(VecSetSizes(x, PETSC_DECIDE, n));
22: PetscCall(VecSetFromOptions(x));
23: PetscCall(VecSet(x, 1.0));
25: /* Create a corresponding n x n centering matrix and use it to create a mean-centered y = C * x. */
26: PetscCall(VecDuplicate(x, &y));
27: PetscCall(MatCreateCentering(PETSC_COMM_WORLD, PETSC_DECIDE, n, &C));
28: PetscCall(MatMult(C, x, y));
30: /* Verify that the centered vector y has norm 0. */
31: PetscCall(VecNorm(y, NORM_2, &norm));
32: PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Vector norm after MatMult() with centering matrix applied to vector of ones is %f.\n", (double)norm));
34: /* Now repeat, but using MatMultTranspose(). */
35: PetscCall(MatMultTranspose(C, x, y));
36: PetscCall(VecNorm(y, NORM_2, &norm));
37: PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Vector norm after MatMultTranspose() with centering matrix applied to vector of ones is %f.\n", (double)norm));
39: /* Clean up. */
40: PetscCall(VecDestroy(&x));
41: PetscCall(VecDestroy(&y));
42: PetscCall(MatDestroy(&C));
43: PetscCall(PetscFinalize());
44: return 0;
45: }
47: /*TEST
49: test:
50: suffix: 1
51: nsize: 1
52: output_file: output/ex247.out
54: test:
55: suffix: 2
56: nsize: 2
57: output_file: output/ex247.out
59: TEST*/