1 /* 2 * 3 * Created on: Sep 25, 2017 4 * Author: Fande Kong 5 */ 6 7 static char help[] = "Illustrate the use of MatResetPreallocation.\n"; 8 9 #include "petscmat.h" 10 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; 17 18 ierr = PetscInitialize(&argc,&argv,0,help);if (ierr) return ierr; 19 comm = MPI_COMM_WORLD; 20 ierr = PetscMalloc2(m,&dnnz,m,&onnz);CHKERRQ(ierr); 21 for (i=0; i<m; i++) { 22 dnnz[i] = 1; 23 onnz[i] = 1; 24 } 25 ierr = MatCreateAIJ(comm,m,n,PETSC_DETERMINE,PETSC_DETERMINE,PETSC_DECIDE,dnnz,PETSC_DECIDE,onnz,&A);CHKERRQ(ierr); 26 ierr = MatSetFromOptions(A);CHKERRQ(ierr); 27 ierr = MatSetUp(A);CHKERRQ(ierr); 28 ierr = PetscFree2(dnnz,onnz);CHKERRQ(ierr); 29 30 /* This assembly shrinks memory because we do not insert enough number of values */ 31 ierr = MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr); 32 ierr = MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr); 33 34 /* MatResetPreallocation restores the memory required by users */ 35 ierr = MatResetPreallocation(A);CHKERRQ(ierr); 36 ierr = MatSetOption(A,MAT_NEW_NONZERO_ALLOCATION_ERR,PETSC_TRUE);CHKERRQ(ierr); 37 ierr = MatGetOwnershipRange(A,&rstart,&rend);CHKERRQ(ierr); 38 ierr = MatGetSize(A,&M,&N);CHKERRQ(ierr); 39 for (i=rstart; i<rend; i++) { 40 ierr = MatSetValue(A,i,i,2.0,INSERT_VALUES);CHKERRQ(ierr); 41 if (rend<N) { 42 ierr = MatSetValue(A,i,rend,1.0,INSERT_VALUES);CHKERRQ(ierr); 43 } 44 } 45 ierr = MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr); 46 ierr = MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr); 47 ierr = MatView(A,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr); 48 ierr = MatDestroy(&A);CHKERRQ(ierr); 49 ierr = PetscFinalize(); 50 return ierr; 51 } 52 53 /*TEST 54 55 test: 56 suffix: 1 57 58 test: 59 suffix: 2 60 nsize: 2 61 62 TEST*/ 63