Actual source code: ex4.c
1: /*
2: *
3: * Created on: Sep 25, 2017
4: * Author: Fande Kong
5: */
7: static char help[] = "Illustrate the use of MatResetPreallocation.\n";
9: #include "petscmat.h"
11: int main(int argc, char **argv)
12: {
13: Mat A;
14: MPI_Comm comm;
15: PetscInt n = 5, m = 5, *dnnz, *onnz, i, rstart, rend, M, N;
18: PetscInitialize(&argc, &argv, 0, help);
19: comm = MPI_COMM_WORLD;
20: PetscMalloc2(m, &dnnz, m, &onnz);
21: for (i = 0; i < m; i++) {
22: dnnz[i] = 1;
23: onnz[i] = 1;
24: }
25: MatCreateAIJ(comm, m, n, PETSC_DETERMINE, PETSC_DETERMINE, PETSC_DECIDE, dnnz, PETSC_DECIDE, onnz, &A);
26: MatSetFromOptions(A);
27: MatSetUp(A);
28: PetscFree2(dnnz, onnz);
30: /* This assembly shrinks memory because we do not insert enough number of values */
31: MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY);
32: MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY);
34: /* MatResetPreallocation restores the memory required by users */
35: MatResetPreallocation(A);
36: MatSetOption(A, MAT_NEW_NONZERO_ALLOCATION_ERR, PETSC_TRUE);
37: MatGetOwnershipRange(A, &rstart, &rend);
38: MatGetSize(A, &M, &N);
39: for (i = rstart; i < rend; i++) {
40: MatSetValue(A, i, i, 2.0, INSERT_VALUES);
41: if (rend < N) MatSetValue(A, i, rend, 1.0, INSERT_VALUES);
42: }
43: MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY);
44: MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY);
45: MatView(A, PETSC_VIEWER_STDOUT_WORLD);
46: MatDestroy(&A);
47: PetscFinalize();
48: return 0;
49: }
51: /*TEST
53: test:
54: suffix: 1
56: test:
57: suffix: 2
58: nsize: 2
60: TEST*/