2: static char help[] = "Tests repeated use of assembly for matrices.\n\n";

  4:  #include <petscmat.h>

  6: int main(int argc,char **args)
  7: {
  8:   Mat            C;
  9:   PetscInt       i,j,m = 5,n = 2,Ii,J;
 11:   PetscMPIInt    rank,size;
 12:   PetscScalar    v;

 14:   PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr;
 15:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
 16:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 17:   n    = 2*size;

 19:   /* create the matrix for the five point stencil, YET AGAIN*/
 20:   MatCreate(PETSC_COMM_WORLD,&C);
 21:   MatSetSizes(C,PETSC_DECIDE,PETSC_DECIDE,m*n,m*n);
 22:   MatSetFromOptions(C);
 23:   MatSetUp(C);
 24:   for (i=0; i<m; i++) {
 25:     for (j=2*rank; j<2*rank+2; j++) {
 26:       v = -1.0;  Ii = j + n*i;
 27:       if (i>0)   {J = Ii - n; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 28:       if (i<m-1) {J = Ii + n; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 29:       if (j>0)   {J = Ii - 1; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 30:       if (j<n-1) {J = Ii + 1; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 31:       v = 4.0; MatSetValues(C,1,&Ii,1,&Ii,&v,INSERT_VALUES);
 32:     }
 33:   }
 34:   MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
 35:   MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);
 36:   for (i=0; i<m; i++) {
 37:     for (j=2*rank; j<2*rank+2; j++) {
 38:       v = 1.0;  Ii = j + n*i;
 39:       if (i>0)   {J = Ii - n; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 40:       if (i<m-1) {J = Ii + n; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 41:       if (j>0)   {J = Ii - 1; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 42:       if (j<n-1) {J = Ii + 1; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 43:       v = -4.0; MatSetValues(C,1,&Ii,1,&Ii,&v,INSERT_VALUES);
 44:     }
 45:   }
 46:   MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
 47:   MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);

 49:   MatView(C,PETSC_VIEWER_STDOUT_WORLD);

 51:   MatDestroy(&C);
 52:   PetscFinalize();
 53:   return ierr;
 54: }