2: static char help[] = "Tests the use of MatZeroRows() for uniprocessor matrices.\n\n";

 4:  #include petscmat.h

  8: int main(int argc,char **args)
  9: {
 10:   Mat            C;
 11:   PetscInt       i,j,m = 5,n = 5,Ii,J;
 13:   PetscScalar    v,five = 5.0;
 14:   IS             isrow;
 15:   PetscTruth     keepzeroedrows;

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

 19:   /* create the matrix for the five point stencil, YET AGAIN*/
 20:   MatCreate(PETSC_COMM_SELF,&C);
 21:   MatSetSizes(C,PETSC_DECIDE,PETSC_DECIDE,m*n,m*n);
 22:   MatSetFromOptions(C);
 23:   for (i=0; i<m; i++) {
 24:     for (j=0; j<n; j++) {
 25:       v = -1.0;  Ii = j + n*i;
 26:       if (i>0)   {J = Ii - n; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 27:       if (i<m-1) {J = Ii + n; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 28:       if (j>0)   {J = Ii - 1; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 29:       if (j<n-1) {J = Ii + 1; MatSetValues(C,1,&Ii,1,&J,&v,INSERT_VALUES);}
 30:       v = 4.0; MatSetValues(C,1,&Ii,1,&Ii,&v,INSERT_VALUES);
 31:     }
 32:   }
 33:   MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
 34:   MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);

 36:   ISCreateStride(PETSC_COMM_SELF,(m*n)/2,0,2,&isrow);

 38:   PetscOptionsHasName(PETSC_NULL,"-keep_zeroed_rows",&keepzeroedrows);
 39:   if (keepzeroedrows) {
 40:     MatSetOption(C,MAT_KEEP_ZEROED_ROWS);
 41:   }

 43:   MatZeroRowsIS(C,isrow,five);

 45:   MatView(C,PETSC_VIEWER_STDOUT_SELF);

 47:   ISDestroy(isrow);
 48:   MatDestroy(C);
 49:   PetscFinalize();
 50:   return 0;
 51: }