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;

 17:   PetscInitialize(&argc,&argv,0,help);
 18:   comm = MPI_COMM_WORLD;
 19:   PetscMalloc2(m,&dnnz,m,&onnz);
 20:   for (i=0; i<m; i++) {
 21:     dnnz[i] = 1;
 22:     onnz[i] = 1;
 23:   }
 24:   MatCreateAIJ(comm,m,n,PETSC_DETERMINE,PETSC_DETERMINE,PETSC_DECIDE,dnnz,PETSC_DECIDE,onnz,&A);
 25:   MatSetFromOptions(A);
 26:   MatSetUp(A);
 27:   PetscFree2(dnnz,onnz);

 29:   /* This assembly shrinks memory because we do not insert enough number of values */
 30:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
 31:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);

 33:   /* MatResetPreallocation restores the memory required by users */
 34:   MatResetPreallocation(A);
 35:   MatSetOption(A,MAT_NEW_NONZERO_ALLOCATION_ERR,PETSC_TRUE);
 36:   MatGetOwnershipRange(A,&rstart,&rend);
 37:   MatGetSize(A,&M,&N);
 38:   for (i=rstart; i<rend; i++) {
 39:     MatSetValue(A,i,i,2.0,INSERT_VALUES);
 40:     if (rend<N) {
 41:       MatSetValue(A,i,rend,1.0,INSERT_VALUES);
 42:     }
 43:   }
 44:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
 45:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
 46:   MatView(A,PETSC_VIEWER_STDOUT_WORLD);
 47:   MatDestroy(&A);
 48:   PetscFinalize();
 49:   return 0;
 50: }

 52: /*TEST

 54:    test:
 55:       suffix: 1

 57:    test:
 58:       suffix: 2
 59:       nsize: 2

 61: TEST*/