Actual source code: ex4.c
petsc-3.10.5 2019-03-28
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;
16: PetscErrorCode ierr;
18: PetscInitialize(&argc,&argv,0,help);if (ierr) return ierr;
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) {
42: MatSetValue(A,i,rend,1.0,INSERT_VALUES);
43: }
44: }
45: MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
46: MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
47: MatView(A,PETSC_VIEWER_STDOUT_WORLD);
48: MatDestroy(&A);
49: PetscFinalize();
50: return ierr;
51: }
53: /*TEST
55: test:
56: suffix: 1
58: test:
59: suffix: 2
60: nsize: 2
62: TEST*/