1 /*
2 Contributed by: Fande Kong
3 */
4
5 static char help[] = "Illustrate the use of MatResetPreallocation.\n";
6
7 #include <petscmat.h>
8
main(int argc,char ** argv)9 int main(int argc, char **argv)
10 {
11 Mat A;
12 MPI_Comm comm;
13 PetscInt n = 5, m = 5, *dnnz, *onnz, i, rstart, rend, M, N;
14
15 PetscFunctionBeginUser;
16 PetscCall(PetscInitialize(&argc, &argv, 0, help));
17 comm = MPI_COMM_WORLD;
18 PetscCall(PetscMalloc2(m, &dnnz, m, &onnz));
19 for (i = 0; i < m; i++) {
20 dnnz[i] = 1;
21 onnz[i] = 1;
22 }
23 PetscCall(MatCreateAIJ(comm, m, n, PETSC_DETERMINE, PETSC_DETERMINE, PETSC_DECIDE, dnnz, PETSC_DECIDE, onnz, &A));
24 PetscCall(MatSetFromOptions(A));
25 PetscCall(MatSetUp(A));
26 PetscCall(PetscFree2(dnnz, onnz));
27
28 /* since the matrix has never been assembled this reset should do nothing */
29 PetscCall(MatResetPreallocation(A));
30
31 /* This assembly shrinks memory because we do not insert enough number of values */
32 PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
33 PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
34
35 /* MatResetPreallocation() restores the memory required by users */
36 PetscCall(MatResetPreallocation(A));
37 PetscCall(MatSetOption(A, MAT_NEW_NONZERO_ALLOCATION_ERR, PETSC_TRUE));
38 PetscCall(MatGetOwnershipRange(A, &rstart, &rend));
39 PetscCall(MatGetSize(A, &M, &N));
40 for (i = rstart; i < rend; i++) {
41 PetscCall(MatSetValue(A, i, i, 2.0, INSERT_VALUES));
42 if (rend < N) PetscCall(MatSetValue(A, i, rend, 1.0, INSERT_VALUES));
43 }
44 PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
45 PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
46 PetscCall(MatView(A, PETSC_VIEWER_STDOUT_WORLD));
47 PetscCall(MatDestroy(&A));
48 PetscCall(PetscFinalize());
49 return 0;
50 }
51
52 /*TEST
53
54 test:
55 suffix: 1
56
57 test:
58 suffix: 2
59 nsize: 2
60
61 TEST*/
62