1 /* 2 Contributed by: Fande Kong 3 */ 4 5 static char help[] = "Illustrate the use of MatResetPreallocation.\n"; 6 7 #include <petscmat.h> 8 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