
static char help[] = "Tests the parallel case for MatIncreaseOverlap(). Input arguments are:\n\
  -f <input_file> : file to load.  For example see $PETSC_DIR/share/petsc/datafiles/matrices\n\
  -nd <size>      : > 0  number of domains per processor \n\
  -ov <overlap>   : >=0  amount of overlap between domains\n\n";

#include <petscmat.h>

#undef __FUNCT__
#define __FUNCT__ "main"
int main(int argc,char **args)
{
  PetscErrorCode ierr;
  PetscInt       nd = 2,ov=1,i,start,m,n,end,lsize;
  PetscMPIInt    rank;
  PetscBool      flg;
  Mat            A,B;
  char           file[PETSC_MAX_PATH_LEN];
  PetscViewer    fd;
  IS             *is1,*is2;
  PetscRandom    r;
  PetscScalar    rand;

  PetscInitialize(&argc,&args,(char*)0,help);
#if defined(PETSC_USE_COMPLEX)
  SETERRQ(PETSC_COMM_WORLD,1,"This example does not work with complex numbers");
#else

  ierr = MPI_Comm_rank(PETSC_COMM_WORLD,&rank);CHKERRQ(ierr);
  ierr = PetscOptionsGetString(NULL,"-f",file,PETSC_MAX_PATH_LEN,&flg);CHKERRQ(ierr);
  if (!flg) SETERRQ(PETSC_COMM_WORLD,1,"Must use -f filename to indicate a file containing a PETSc binary matrix");
  ierr = PetscOptionsGetInt(NULL,"-nd",&nd,NULL);CHKERRQ(ierr);
  ierr = PetscOptionsGetInt(NULL,"-ov",&ov,NULL);CHKERRQ(ierr);

  /* Read matrix and RHS */
  ierr = PetscViewerBinaryOpen(PETSC_COMM_WORLD,file,FILE_MODE_READ,&fd);CHKERRQ(ierr);
  ierr = MatCreate(PETSC_COMM_WORLD,&A);CHKERRQ(ierr);
  ierr = MatSetType(A,MATMPIAIJ);CHKERRQ(ierr);
  ierr = MatLoad(A,fd);CHKERRQ(ierr);
  ierr = PetscViewerDestroy(&fd);CHKERRQ(ierr);

  /* Read the matrix again as a sequential matrix */
  ierr = PetscViewerBinaryOpen(PETSC_COMM_SELF,file,FILE_MODE_READ,&fd);CHKERRQ(ierr);
  ierr = MatCreate(PETSC_COMM_SELF,&B);CHKERRQ(ierr);
  ierr = MatSetType(B,MATSEQAIJ);CHKERRQ(ierr);
  ierr = MatLoad(B,fd);CHKERRQ(ierr);
  ierr = PetscViewerDestroy(&fd);CHKERRQ(ierr);

  /* Create the IS corresponding to subdomains */
  ierr = PetscMalloc(nd*sizeof(IS **),&is1);CHKERRQ(ierr);
  ierr = PetscMalloc(nd*sizeof(IS **),&is2);CHKERRQ(ierr);

  /* Create the random Index Sets */
  ierr = MatGetSize(A,&m,&n);CHKERRQ(ierr);
  ierr = PetscRandomCreate(PETSC_COMM_SELF,&r);CHKERRQ(ierr);
  ierr = PetscRandomSetFromOptions(r);CHKERRQ(ierr);
  for (i=0; i<nd; i++) {
    ierr  = PetscRandomGetValue(r,&rand);CHKERRQ(ierr);
    start = (PetscInt)(rand*m);
    ierr  = PetscRandomGetValue(r,&rand);CHKERRQ(ierr);
    end   = (PetscInt)(rand*m);
    lsize =  end - start;
    if (start > end) { start = end; lsize = -lsize;}
    ierr = ISCreateStride(PETSC_COMM_SELF,lsize,start,1,is1+i);CHKERRQ(ierr);
    ierr = ISCreateStride(PETSC_COMM_SELF,lsize,start,1,is2+i);CHKERRQ(ierr);
  }
  ierr = MatIncreaseOverlap(A,nd,is1,ov);CHKERRQ(ierr);
  ierr = MatIncreaseOverlap(B,nd,is2,ov);CHKERRQ(ierr);



  /* Now see if the serial and parallel case have the same answers */
  for (i=0; i<nd; ++i) {
    ierr = ISEqual(is1[i],is2[i],&flg);CHKERRQ(ierr);
    ierr = PetscPrintf(PETSC_COMM_SELF,"proc:[%d], i=%D, flg =%d\n",rank,i,(int)flg);CHKERRQ(ierr);
  }

  /* Free allocated memory */
  for (i=0; i<nd; ++i) {
    ierr = ISDestroy(&is1[i]);CHKERRQ(ierr);
    ierr = ISDestroy(&is2[i]);CHKERRQ(ierr);
  }
  ierr = PetscFree(is1);CHKERRQ(ierr);
  ierr = PetscFree(is2);CHKERRQ(ierr);
  ierr = PetscRandomDestroy(&r);CHKERRQ(ierr);
  ierr = MatDestroy(&A);CHKERRQ(ierr);
  ierr = MatDestroy(&B);CHKERRQ(ierr);

  ierr = PetscFinalize();
#endif
  return 0;
}

