2: static char help[] = "Tests copying an AIJ matrix.\n\n";

  4: #include <petscmat.h>

  8: int main(int argc,char **args)
  9: {
 10:   Mat            C,A;
 11:   PetscInt       i,j,m = 5,n = 5,Ii,J;
 13:   PetscScalar    v;

 15:   PetscInitialize(&argc,&args,(char*)0,help);

 17:   /* create the matrix for the five point stencil, YET AGAIN*/
 18:   MatCreateSeqAIJ(PETSC_COMM_SELF,m*n,m*n,5,NULL,&C);
 19:   MatSetUp(C);
 20:   for (i=0; i<m; i++) {
 21:     for (j=0; j<n; j++) {
 22:       v = -1.0;  Ii = j + n*i;
 23:       if (i>0)   {J = Ii - n; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 24:       if (i<m-1) {J = Ii + n; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 25:       if (j>0)   {J = Ii - 1; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 26:       if (j<n-1) {J = Ii + 1; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 27:       v = 4.0; MatSetValues(C,1,&Ii,1,&Ii,&v,INSERT_VALUES);
 28:     }
 29:   }
 30:   MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
 31:   MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);

 33:   MatConvert(C,MATSAME,MAT_INITIAL_MATRIX,&A);

 35:   for (i=0; i<m; i++) {
 36:     for (j=0; j<n; j++) {
 37:       v = -1.0;  Ii = j + n*i;
 38:       if (i>0)   {J = Ii - n; MatSetValues(A,1,&Ii,1,&J,&v,ADD_VALUES);}
 39:       if (i<m-1) {J = Ii + n; MatSetValues(A,1,&Ii,1,&J,&v,ADD_VALUES);}
 40:       if (j>0)   {J = Ii - 1; MatSetValues(A,1,&Ii,1,&J,&v,ADD_VALUES);}
 41:       if (j<n-1) {J = Ii + 1; MatSetValues(A,1,&Ii,1,&J,&v,ADD_VALUES);}
 42:       v = 4.0; MatSetValues(A,1,&Ii,1,&Ii,&v,ADD_VALUES);
 43:     }
 44:   }
 45:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
 46:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);

 48:   MatView(A,PETSC_VIEWER_STDOUT_SELF);

 50:   MatDestroy(&C);
 51:   MatDestroy(&A);
 52:   PetscFinalize();
 53:   return 0;
 54: }