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

  4:  #include <petscmat.h>

  6: int main(int argc,char **args)
  7: {
  8:   Mat            C,A;
  9:   PetscInt       i,j,m = 5,n = 5,Ii,J;
 11:   PetscScalar    v;

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

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

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

 45:   MatView(A,PETSC_VIEWER_STDOUT_SELF);

 47:   MatDestroy(&C);
 48:   MatDestroy(&A);
 49:   PetscFinalize();
 50:   return ierr;
 51: }