Beispiel #1
0
Datei: grow.c Projekt: 8l/insieme
hypre_BoxArrayArray *
hypre_GrowBoxArrayByStencil( hypre_BoxArray      *box_array,
                             hypre_StructStencil *stencil,
                             int                  transpose )
{
   hypre_BoxArrayArray     *grow_box_array_array;

   int                      i;

   grow_box_array_array =
      hypre_BoxArrayArrayCreate(hypre_BoxArraySize(box_array));

   hypre_ForBoxI(i, box_array)
      {
         hypre_BoxArrayDestroy(
            hypre_BoxArrayArrayBoxArray(grow_box_array_array, i));
         hypre_BoxArrayArrayBoxArray(grow_box_array_array, i) =
            hypre_GrowBoxByStencil(hypre_BoxArrayBox(box_array, i),
                                   stencil, transpose);
      }
Beispiel #2
0
int
hypre_CreateComputeInfo( hypre_StructGrid      *grid,
                         hypre_StructStencil   *stencil,
                         hypre_ComputeInfo    **compute_info_ptr )
{
   int                      ierr = 0;

   hypre_CommInfo          *comm_info;
   hypre_BoxArrayArray     *indt_boxes;
   hypre_BoxArrayArray     *dept_boxes;

   hypre_BoxArray          *boxes;

   hypre_BoxArray          *cbox_array;
   hypre_Box               *cbox;

   int                      i;

#ifdef HYPRE_OVERLAP_COMM_COMP
   hypre_Box               *rembox;
   hypre_Index             *stencil_shape;
   int                      border[3][2] = {{0, 0}, {0, 0}, {0, 0}};
   int                      cbox_array_size;
   int                      s, d;
#endif

   /*------------------------------------------------------
    * Extract needed grid info
    *------------------------------------------------------*/

   boxes = hypre_StructGridBoxes(grid);

   /*------------------------------------------------------
    * Get communication info
    *------------------------------------------------------*/

   hypre_CreateCommInfoFromStencil(grid, stencil, &comm_info);

#ifdef HYPRE_OVERLAP_COMM_COMP

   /*------------------------------------------------------
    * Compute border info
    *------------------------------------------------------*/

   stencil_shape = hypre_StructStencilShape(stencil);
   for (s = 0; s < hypre_StructStencilSize(stencil); s++)
   {
      for (d = 0; d < 3; d++)
      {
         i = hypre_IndexD(stencil_shape[s], d);
         if (i < 0)
         {
            border[d][0] = hypre_max(border[d][0], -i);
         }
         else if (i > 0)
         {
            border[d][1] = hypre_max(border[d][1], i);
         }
      }
   }

   /*------------------------------------------------------
    * Set up the dependent boxes
    *------------------------------------------------------*/

   dept_boxes = hypre_BoxArrayArrayCreate(hypre_BoxArraySize(boxes));

   rembox = hypre_BoxCreate();
   hypre_ForBoxI(i, boxes)
      {
         cbox_array = hypre_BoxArrayArrayBoxArray(dept_boxes, i);
         hypre_BoxArraySetSize(cbox_array, 6);

         hypre_CopyBox(hypre_BoxArrayBox(boxes, i), rembox);
         cbox_array_size = 0;
         for (d = 0; d < 3; d++)
         {
            if ( (hypre_BoxVolume(rembox)) && (border[d][0]) )
            {
               cbox = hypre_BoxArrayBox(cbox_array, cbox_array_size);
               hypre_CopyBox(rembox, cbox);
               hypre_BoxIMaxD(cbox, d) =
                  hypre_BoxIMinD(cbox, d) + border[d][0] - 1;
               hypre_BoxIMinD(rembox, d) =
                  hypre_BoxIMinD(cbox, d) + border[d][0];
               cbox_array_size++;
            }
            if ( (hypre_BoxVolume(rembox)) && (border[d][1]) )
            {
               cbox = hypre_BoxArrayBox(cbox_array, cbox_array_size);
               hypre_CopyBox(rembox, cbox);
               hypre_BoxIMinD(cbox, d) =
                  hypre_BoxIMaxD(cbox, d) - border[d][1] + 1;
               hypre_BoxIMaxD(rembox, d) =
                  hypre_BoxIMaxD(cbox, d) - border[d][1];
               cbox_array_size++;
            }
         }
         hypre_BoxArraySetSize(cbox_array, cbox_array_size);
      }
Beispiel #3
0
               hypre_BoxIMinD(cbox, d) =
                  hypre_BoxIMaxD(cbox, d) - border[d][1] + 1;
               hypre_BoxIMaxD(rembox, d) =
                  hypre_BoxIMaxD(cbox, d) - border[d][1];
               cbox_array_size++;
            }
         }
         hypre_BoxArraySetSize(cbox_array, cbox_array_size);
      }
   hypre_BoxDestroy(rembox);

   /*------------------------------------------------------
    * Set up the independent boxes
    *------------------------------------------------------*/

   indt_boxes = hypre_BoxArrayArrayCreate(hypre_BoxArraySize(boxes));

   hypre_ForBoxI(i, boxes)
      {
         cbox_array = hypre_BoxArrayArrayBoxArray(indt_boxes, i);
         hypre_BoxArraySetSize(cbox_array, 1);
         cbox = hypre_BoxArrayBox(cbox_array, 0);
         hypre_CopyBox(hypre_BoxArrayBox(boxes, i), cbox);

         for (d = 0; d < 3; d++)
         {
            if ( (border[d][0]) )
            {
               hypre_BoxIMinD(cbox, d) += border[d][0];
            }
            if ( (border[d][1]) )
hypre_SStructSendInfoData *
hypre_SStructSendInfo( hypre_StructGrid      *fgrid,
                       hypre_BoxManager      *cboxman,
                       hypre_Index            rfactor )
{
   hypre_SStructSendInfoData *sendinfo_data;

   MPI_Comm                   comm= hypre_SStructVectorComm(fgrid);

   hypre_BoxArray            *grid_boxes;
   hypre_Box                 *grid_box, cbox;
   hypre_Box                 *intersect_box, boxman_entry_box;

   hypre_BoxManEntry        **boxman_entries;
   HYPRE_Int                  nboxman_entries;

   hypre_BoxArrayArray       *send_boxes;
   HYPRE_Int                **send_processes;
   HYPRE_Int                **send_remote_boxnums;

   hypre_Index                ilower, iupper, index;

   HYPRE_Int                  myproc, proc;

   HYPRE_Int                  cnt;
   HYPRE_Int                  i, j;

   hypre_ClearIndex(index); 
   hypre_MPI_Comm_rank(comm, &myproc);

   sendinfo_data= hypre_CTAlloc(hypre_SStructSendInfoData, 1);

   /*------------------------------------------------------------------------
    * Create the structured sendbox patterns. 
    *
    *   send_boxes are obtained by intersecting this proc's fgrid boxes
    *   with cgrid's box_man. Intersecting BoxManEntries not on this proc
    *   will give boxes that we will need to send data to- i.e., we scan
    *   through the boxes of grid and find the processors that own a chunk
    *   of it.
    *------------------------------------------------------------------------*/
   intersect_box = hypre_CTAlloc(hypre_Box, 1);
   grid_boxes   = hypre_StructGridBoxes(fgrid);

   send_boxes= hypre_BoxArrayArrayCreate(hypre_BoxArraySize(grid_boxes));
   send_processes= hypre_CTAlloc(HYPRE_Int *, hypre_BoxArraySize(grid_boxes));
   send_remote_boxnums= hypre_CTAlloc(HYPRE_Int *, hypre_BoxArraySize(grid_boxes));

   hypre_ForBoxI(i, grid_boxes)
   {
       grid_box= hypre_BoxArrayBox(grid_boxes, i);

       /*---------------------------------------------------------------------
        * Find the boxarray that must be sent. BoxManIntersect returns
        * the full extents of the boxes that intersect with the given box.
        * We further need to intersect each box in the list with the given
        * box to determine the actual box that needs to be sent.
        *---------------------------------------------------------------------*/
       hypre_SStructIndexScaleF_C(hypre_BoxIMin(grid_box), index,
                                  rfactor, hypre_BoxIMin(&cbox));
       hypre_SStructIndexScaleF_C(hypre_BoxIMax(grid_box), index,
                                  rfactor, hypre_BoxIMax(&cbox));

       hypre_BoxManIntersect(cboxman, hypre_BoxIMin(&cbox), hypre_BoxIMax(&cbox),
                            &boxman_entries, &nboxman_entries);

       cnt= 0;
       for (j= 0; j< nboxman_entries; j++)
       {
          hypre_SStructBoxManEntryGetProcess(boxman_entries[j], &proc);
          if (proc != myproc)
          {
             cnt++;
          }
       }
       send_processes[i]     = hypre_CTAlloc(HYPRE_Int, cnt);
       send_remote_boxnums[i]= hypre_CTAlloc(HYPRE_Int, cnt);

       cnt= 0;
       for (j= 0; j< nboxman_entries; j++)
       {
          hypre_SStructBoxManEntryGetProcess(boxman_entries[j], &proc);

          /* determine the chunk of the boxman_entries[j] box that is needed */
          hypre_BoxManEntryGetExtents(boxman_entries[j], ilower, iupper);
          hypre_BoxSetExtents(&boxman_entry_box, ilower, iupper);
          hypre_IntersectBoxes(&boxman_entry_box, &cbox, &boxman_entry_box);

          if (proc != myproc)
          {
             send_processes[i][cnt]     = proc;
             hypre_SStructBoxManEntryGetBoxnum(boxman_entries[j], 
                                            &send_remote_boxnums[i][cnt]);
             hypre_AppendBox(&boxman_entry_box, 
                              hypre_BoxArrayArrayBoxArray(send_boxes, i));
             cnt++;
          }
      } 
      hypre_TFree(boxman_entries);
   }  /* hypre_ForBoxI(i, grid_boxes) */ 
Beispiel #5
0
HYPRE_Int
hypre_AMR_CFCoarsen( hypre_SStructMatrix  *   A,
                     hypre_SStructMatrix  *   fac_A,
                     hypre_Index              refine_factors,
                     HYPRE_Int                level ) 

{
   MPI_Comm                comm       = hypre_SStructMatrixComm(A);
   hypre_SStructGraph     *graph      = hypre_SStructMatrixGraph(A);
   HYPRE_Int               graph_type = hypre_SStructGraphObjectType(graph);
   hypre_SStructGrid      *grid       = hypre_SStructGraphGrid(graph);
   HYPRE_Int               nUventries = hypre_SStructGraphNUVEntries(graph);
   HYPRE_IJMatrix          ij_A       = hypre_SStructMatrixIJMatrix(A);
   HYPRE_Int               matrix_type= hypre_SStructMatrixObjectType(A);
   HYPRE_Int               ndim       = hypre_SStructMatrixNDim(A);

   hypre_SStructPMatrix   *A_pmatrix;
   hypre_StructMatrix     *smatrix_var;
   hypre_StructStencil    *stencils;
   HYPRE_Int               stencil_size;
   hypre_Index             stencil_shape_i;
   hypre_Index             loop_size;
   hypre_Box               refined_box;
   double                **a_ptrs;
   hypre_Box              *A_dbox;

   HYPRE_Int               part_crse= level-1;
   HYPRE_Int               part_fine= level;
 
   hypre_BoxManager       *fboxman;
   hypre_BoxManEntry     **boxman_entries, *boxman_entry;
   HYPRE_Int               nboxman_entries;
   hypre_Box               boxman_entry_box;

   hypre_BoxArrayArray  ***fgrid_cinterface_extents;

   hypre_StructGrid       *cgrid;
   hypre_BoxArray         *cgrid_boxes;
   hypre_Box              *cgrid_box;
   hypre_Index             node_extents;
   hypre_Index             stridec, stridef;

   hypre_BoxArrayArray    *cinterface_arrays;
   hypre_BoxArray         *cinterface_array;
   hypre_Box              *fgrid_cinterface;

   HYPRE_Int               centre;

   HYPRE_Int               ci, fi, boxi;
   HYPRE_Int               max_stencil_size= 27;
   HYPRE_Int               false= 0;
   HYPRE_Int               true = 1;
   HYPRE_Int               found;
   HYPRE_Int              *stencil_ranks, *rank_stencils;
   HYPRE_Int               rank, startrank;
   double                 *vals;

   HYPRE_Int               i, j, iA;
   HYPRE_Int               nvars, var1; 

   hypre_Index             lindex, zero_index;
   hypre_Index             index1, index2;
   hypre_Index             index_temp;

   hypre_SStructUVEntry   *Uventry;
   HYPRE_Int               nUentries, cnt1;
   HYPRE_Int               box_array_size;

   HYPRE_Int              *ncols, *rows, *cols;
   
   HYPRE_Int              *temp1, *temp2;

   HYPRE_Int               myid;

   hypre_MPI_Comm_rank(comm, &myid);
   hypre_SetIndex(zero_index, 0, 0, 0);
   
   /*--------------------------------------------------------------------------
    *  Task: Coarsen the CF interface connections of A into fac_A so that 
    *  fac_A will have the stencil coefficients extending into a coarsened
    *  fbox. The centre coefficient is constructed to preserve the row sum.
    *--------------------------------------------------------------------------*/

   if (graph_type == HYPRE_SSTRUCT)
   {
      startrank   = hypre_SStructGridGhstartRank(grid);
   }
   if (graph_type == HYPRE_PARCSR)
   {
      startrank   = hypre_SStructGridStartRank(grid);
   }

   /*--------------------------------------------------------------------------
    * Fine grid strides by the refinement factors.
    *--------------------------------------------------------------------------*/
   hypre_SetIndex(stridec, 1, 1, 1);
   for (i= 0; i< ndim; i++)
   {
      stridef[i]= refine_factors[i];
   }
   for (i= ndim; i< 3; i++)
   {
      stridef[i]= 1;
   }

   /*--------------------------------------------------------------------------
    *  Determine the c/f interface index boxes: fgrid_cinterface_extents.
    *  These are between fpart= level and cpart= (level-1). The 
    *  fgrid_cinterface_extents are indexed by cboxes, but fboxes that
    *  abutt a given cbox must be considered. Moreover, for each fbox,
    *  we can have a c/f interface from a number of different stencil
    *  directions- i.e., we have a boxarrayarray for each cbox, each
    *  fbox leading to a boxarray.
    *
    *  Algo.: For each cbox:
    *    1) refine & stretch by a unit in each dimension.
    *    2) boxman_intersect with the fgrid boxman to get all fboxes contained
    *       or abutting this cbox.
    *    3) get the fgrid_cinterface_extents for each of these fboxes.
    *
    *  fgrid_cinterface_extents[var1][ci]
    *--------------------------------------------------------------------------*/
   A_pmatrix=  hypre_SStructMatrixPMatrix(fac_A, part_crse);
   nvars    =  hypre_SStructPMatrixNVars(A_pmatrix);

   fgrid_cinterface_extents= hypre_TAlloc(hypre_BoxArrayArray **, nvars);
   for (var1= 0; var1< nvars; var1++)
   {
      fboxman= hypre_SStructGridBoxManager(grid, part_fine, var1);
      stencils= hypre_SStructPMatrixSStencil(A_pmatrix, var1, var1);

      cgrid= hypre_SStructPGridSGrid(hypre_SStructPMatrixPGrid(A_pmatrix), var1);
      cgrid_boxes= hypre_StructGridBoxes(cgrid); 
      fgrid_cinterface_extents[var1]= hypre_TAlloc(hypre_BoxArrayArray *, 
                                                   hypre_BoxArraySize(cgrid_boxes));

      hypre_ForBoxI(ci, cgrid_boxes)
      {
         cgrid_box= hypre_BoxArrayBox(cgrid_boxes, ci);

         hypre_StructMapCoarseToFine(hypre_BoxIMin(cgrid_box), zero_index,
                                     refine_factors, hypre_BoxIMin(&refined_box));
         hypre_SetIndex(index1, refine_factors[0]-1, refine_factors[1]-1,
                        refine_factors[2]-1);
         hypre_StructMapCoarseToFine(hypre_BoxIMax(cgrid_box), index1,
                                     refine_factors, hypre_BoxIMax(&refined_box));

         /*------------------------------------------------------------------------
          * Stretch the refined_box so that a BoxManIntersect will get abutting
          * fboxes.
          *------------------------------------------------------------------------*/
         for (i= 0; i< ndim; i++)
         {
            hypre_BoxIMin(&refined_box)[i]-= 1;
            hypre_BoxIMax(&refined_box)[i]+= 1;
         }

         hypre_BoxManIntersect(fboxman, hypre_BoxIMin(&refined_box),
                               hypre_BoxIMax(&refined_box), &boxman_entries,
                               &nboxman_entries);

         fgrid_cinterface_extents[var1][ci]= hypre_BoxArrayArrayCreate(nboxman_entries);

         /*------------------------------------------------------------------------
          * Get the  fgrid_cinterface_extents using var1-var1 stencil (only like-
          * variables couple).
          *------------------------------------------------------------------------*/
         if (stencils != NULL)
         {
            for (i= 0; i< nboxman_entries; i++)
            {
               hypre_BoxManEntryGetExtents(boxman_entries[i],
                                           hypre_BoxIMin(&boxman_entry_box),
                                           hypre_BoxIMax(&boxman_entry_box));
               hypre_CFInterfaceExtents2(&boxman_entry_box, cgrid_box, stencils, refine_factors,
                                         hypre_BoxArrayArrayBoxArray(fgrid_cinterface_extents[var1][ci], i) );
            }
         }
         hypre_TFree(boxman_entries);

      }  /* hypre_ForBoxI(ci, cgrid_boxes) */
   }     /* for (var1= 0; var1< nvars; var1++) */
int
hypre_PointRelaxSetup( void               *relax_vdata,
                       hypre_StructMatrix *A,
                       hypre_StructVector *b,
                       hypre_StructVector *x           )
{
   hypre_PointRelaxData *relax_data = (hypre_PointRelaxData *)relax_vdata;

   int                    num_pointsets    = (relax_data -> num_pointsets);
   int                   *pointset_sizes   = (relax_data -> pointset_sizes);
   hypre_Index           *pointset_strides = (relax_data -> pointset_strides);
   hypre_Index          **pointset_indices = (relax_data -> pointset_indices);
   hypre_StructVector    *t;
   int                    diag_rank;
   hypre_ComputePkg     **compute_pkgs;

   hypre_Index            unit_stride;
   hypre_Index            diag_index;
   hypre_IndexRef         stride;
   hypre_IndexRef         index;
                       
   hypre_StructGrid      *grid;
   hypre_StructStencil   *stencil;
                       
   hypre_BoxArrayArray   *send_boxes;
   hypre_BoxArrayArray   *recv_boxes;
   int                  **send_processes;
   int                  **recv_processes;
   hypre_BoxArrayArray   *indt_boxes;
   hypre_BoxArrayArray   *dept_boxes;

   hypre_BoxArrayArray   *orig_indt_boxes;
   hypre_BoxArrayArray   *orig_dept_boxes;
   hypre_BoxArrayArray   *box_aa;
   hypre_BoxArray        *box_a;
   hypre_Box             *box;
   int                    box_aa_size;
   int                    box_a_size;
   hypre_BoxArrayArray   *new_box_aa;
   hypre_BoxArray        *new_box_a;
   hypre_Box             *new_box;

   double                 scale;
   int                    frac;

   int                    i, j, k, p, m, compute_i;
   int                    ierr = 0;
                       
   /*----------------------------------------------------------
    * Set up the temp vector
    *----------------------------------------------------------*/

   if ((relax_data -> t) == NULL)
   {
      t = hypre_StructVectorCreate(hypre_StructVectorComm(b),
                                   hypre_StructVectorGrid(b));
      hypre_StructVectorSetNumGhost(t, hypre_StructVectorNumGhost(b));
      hypre_StructVectorInitialize(t);
      hypre_StructVectorAssemble(t);
      (relax_data -> t) = t;
   }

   /*----------------------------------------------------------
    * Find the matrix diagonal
    *----------------------------------------------------------*/

   grid    = hypre_StructMatrixGrid(A);
   stencil = hypre_StructMatrixStencil(A);

   hypre_SetIndex(diag_index, 0, 0, 0);
   diag_rank = hypre_StructStencilElementRank(stencil, diag_index);

   /*----------------------------------------------------------
    * Set up the compute packages
    *----------------------------------------------------------*/

   hypre_SetIndex(unit_stride, 1, 1, 1);

   compute_pkgs = hypre_CTAlloc(hypre_ComputePkg *, num_pointsets);

   for (p = 0; p < num_pointsets; p++)
   {
      hypre_CreateComputeInfo(grid, stencil,
                           &send_boxes, &recv_boxes,
                           &send_processes, &recv_processes,
                           &orig_indt_boxes, &orig_dept_boxes);

      stride = pointset_strides[p];

      for (compute_i = 0; compute_i < 2; compute_i++)
      {
         switch(compute_i)
         {
            case 0:
            box_aa = orig_indt_boxes;
            break;

            case 1:
            box_aa = orig_dept_boxes;
            break;
         }
         box_aa_size = hypre_BoxArrayArraySize(box_aa);
         new_box_aa = hypre_BoxArrayArrayCreate(box_aa_size);

         for (i = 0; i < box_aa_size; i++)
         {
            box_a = hypre_BoxArrayArrayBoxArray(box_aa, i);
            box_a_size = hypre_BoxArraySize(box_a);
            new_box_a = hypre_BoxArrayArrayBoxArray(new_box_aa, i);
            hypre_BoxArraySetSize(new_box_a, box_a_size * pointset_sizes[p]);

            k = 0;
            for (m = 0; m < pointset_sizes[p]; m++)
            {
               index  = pointset_indices[p][m];

               for (j = 0; j < box_a_size; j++)
               {
                  box = hypre_BoxArrayBox(box_a, j);
                  new_box = hypre_BoxArrayBox(new_box_a, k);
                  
                  hypre_CopyBox(box, new_box);
                  hypre_ProjectBox(new_box, index, stride);
                  
                  k++;
               }
            }
         }

         switch(compute_i)
         {
            case 0:
            indt_boxes = new_box_aa;
            break;

            case 1:
            dept_boxes = new_box_aa;
            break;
         }
      }

      hypre_ComputePkgCreate(send_boxes, recv_boxes,
                             unit_stride, unit_stride,
                             send_processes, recv_processes,
                             indt_boxes, dept_boxes,
                             stride, grid,
                             hypre_StructVectorDataSpace(x), 1,
                             &compute_pkgs[p]);

      hypre_BoxArrayArrayDestroy(orig_indt_boxes);
      hypre_BoxArrayArrayDestroy(orig_dept_boxes);
   }

   /*----------------------------------------------------------
    * Set up the relax data structure
    *----------------------------------------------------------*/

   (relax_data -> A) = hypre_StructMatrixRef(A);
   (relax_data -> x) = hypre_StructVectorRef(x);
   (relax_data -> b) = hypre_StructVectorRef(b);
   (relax_data -> diag_rank)    = diag_rank;
   (relax_data -> compute_pkgs) = compute_pkgs;

   /*-----------------------------------------------------
    * Compute flops
    *-----------------------------------------------------*/

   scale = 0.0;
   for (p = 0; p < num_pointsets; p++)
   {
      stride = pointset_strides[p];
      frac   = hypre_IndexX(stride);
      frac  *= hypre_IndexY(stride);
      frac  *= hypre_IndexZ(stride);
      scale += (pointset_sizes[p] / frac);
   }
   (relax_data -> flops) = scale * (hypre_StructMatrixGlobalSize(A) +
                                    hypre_StructVectorGlobalSize(x));

   return ierr;
}
Beispiel #7
0
HYPRE_Int
hypre_CreateCommInfoFromStencil( hypre_StructGrid      *grid,
                                 hypre_StructStencil   *stencil,
                                 hypre_CommInfo       **comm_info_ptr )
{
   HYPRE_Int              i,j,k, d, m, s;   

   hypre_BoxArrayArray   *send_boxes;
   hypre_BoxArrayArray   *recv_boxes;

   HYPRE_Int            **send_procs;
   HYPRE_Int            **recv_procs;
   HYPRE_Int            **send_rboxnums;
   HYPRE_Int            **recv_rboxnums;
   hypre_BoxArrayArray   *send_rboxes;
   hypre_BoxArrayArray   *recv_rboxes;

   hypre_BoxArray        *local_boxes;
   HYPRE_Int              num_boxes;

   HYPRE_Int             *local_ids;

   hypre_BoxManager      *boxman;
                       
   hypre_Index           *stencil_shape;
   hypre_IndexRef         stencil_offset;
   hypre_IndexRef         pshift;
                          
   hypre_Box             *box;
   hypre_Box             *hood_box;
   hypre_Box             *grow_box;
   hypre_Box             *extend_box;
   hypre_Box             *int_box;
   hypre_Box             *periodic_box;
   
   HYPRE_Int              stencil_grid[3][3][3];
   HYPRE_Int              grow[3][2];
                       
   hypre_BoxManEntry    **entries;
   hypre_BoxManEntry     *entry;
   
   HYPRE_Int              num_entries;
   hypre_BoxArray        *neighbor_boxes = NULL;
   HYPRE_Int             *neighbor_procs = NULL;
   HYPRE_Int             *neighbor_ids = NULL;
   HYPRE_Int             *neighbor_shifts = NULL;
   HYPRE_Int              neighbor_count;
   HYPRE_Int              neighbor_alloc;

   hypre_Index            ilower, iupper;

   hypre_BoxArray        *send_box_array;
   hypre_BoxArray        *recv_box_array;
   hypre_BoxArray        *send_rbox_array;
   hypre_BoxArray        *recv_rbox_array;
                       
   hypre_Box            **cboxes;
   hypre_Box             *cboxes_mem;
   HYPRE_Int             *cboxes_neighbor_location;
   HYPRE_Int              num_cboxes, cbox_alloc;
                       
   HYPRE_Int              istart[3], istop[3];
   HYPRE_Int              sgindex[3];               

   HYPRE_Int              num_periods, loc, box_id, id, proc_id;
   HYPRE_Int              myid;
   
   MPI_Comm               comm;

   /*------------------------------------------------------
    * Initializations
    *------------------------------------------------------*/

   local_boxes  = hypre_StructGridBoxes(grid);
   local_ids    = hypre_StructGridIDs(grid);
   num_boxes    = hypre_BoxArraySize(local_boxes);
   num_periods  = hypre_StructGridNumPeriods(grid);
   
   boxman    = hypre_StructGridBoxMan(grid);
   comm      =  hypre_StructGridComm(grid);
   
   hypre_MPI_Comm_rank(comm, &myid);
  
   for (k = 0; k < 3; k++)
   {
      for (j = 0; j < 3; j++)
      {
         for (i = 0; i < 3; i++)
         {
            stencil_grid[i][j][k] = 0;
         }
      }
   }

   /*------------------------------------------------------
    * Compute the "grow" information from the stencil
    *------------------------------------------------------*/

   stencil_shape = hypre_StructStencilShape(stencil);

   for (d = 0; d < 3; d++)
   {
      grow[d][0] = 0;
      grow[d][1] = 0;
   }

   for (s = 0; s < hypre_StructStencilSize(stencil); s++)
   {
      stencil_offset = stencil_shape[s];

      for (d = 0; d < 3; d++)
      {
         m = stencil_offset[d];

         istart[d] = 1;
         istop[d]  = 1;

         if (m < 0)
         {
            istart[d] = 0;
            grow[d][0] = hypre_max(grow[d][0], -m);
         }
         else if (m > 0)
         {
            istop[d] = 2;
            grow[d][1] = hypre_max(grow[d][1],  m);
         }
      }

      /* update stencil grid from the grow_stencil */
      for (k = istart[2]; k <= istop[2]; k++)
      {
         for (j = istart[1]; j <= istop[1]; j++)
         {
            for (i = istart[0]; i <= istop[0]; i++)
            {
               stencil_grid[i][j][k] = 1;
            }
         }
      }
   }

   /*------------------------------------------------------
    * Compute send/recv boxes and procs for each local box
    *------------------------------------------------------*/

   /* initialize: for each local box, we create an array of send/recv info */

   send_boxes = hypre_BoxArrayArrayCreate(num_boxes);
   recv_boxes = hypre_BoxArrayArrayCreate(num_boxes);
   send_procs = hypre_CTAlloc(HYPRE_Int *, num_boxes);
   recv_procs = hypre_CTAlloc(HYPRE_Int *, num_boxes);

   /* Remote boxnums and boxes describe data on the opposing processor, so some
      shifting of boxes is needed below for periodic neighbor boxes.  Remote box
      info is also needed for receives to allow for reverse communication. */
   send_rboxnums = hypre_CTAlloc(HYPRE_Int *, num_boxes);
   send_rboxes   = hypre_BoxArrayArrayCreate(num_boxes);
   recv_rboxnums = hypre_CTAlloc(HYPRE_Int *, num_boxes);
   recv_rboxes   = hypre_BoxArrayArrayCreate(num_boxes);

   grow_box = hypre_BoxCreate();
   extend_box = hypre_BoxCreate();
   int_box  = hypre_BoxCreate();
   periodic_box =  hypre_BoxCreate();
 
   /* storage we will use and keep track of the neighbors */
   neighbor_alloc = 30; /* initial guess at max size */
   neighbor_boxes = hypre_BoxArrayCreate(neighbor_alloc);
   neighbor_procs = hypre_CTAlloc(HYPRE_Int, neighbor_alloc);
   neighbor_ids = hypre_CTAlloc(HYPRE_Int, neighbor_alloc);
   neighbor_shifts = hypre_CTAlloc(HYPRE_Int, neighbor_alloc);

   /* storage we will use to collect all of the intersected boxes (the send and
      recv regions for box i (this may not be enough in the case of periodic
      boxes, so we will have to check) */
   cbox_alloc =  hypre_BoxManNEntries(boxman);

   cboxes_neighbor_location = hypre_CTAlloc(HYPRE_Int, cbox_alloc);
   cboxes = hypre_CTAlloc(hypre_Box *, cbox_alloc);
   cboxes_mem = hypre_CTAlloc(hypre_Box, cbox_alloc);

   /******* loop through each local box **************/

   for (i = 0; i < num_boxes; i++)
   {
      /* get the box */
      box = hypre_BoxArrayBox(local_boxes, i);
      /* box_id = local_ids[i]; the box id in the Box Manager is the box number,
       * and we use this to find out if a box has intersected with itself */
      box_id = i;
      
      /* grow box local i according to the stencil*/
      hypre_CopyBox(box, grow_box);
      for (d = 0; d < 3; d++)
      {
         hypre_BoxIMinD(grow_box, d) -= grow[d][0];
         hypre_BoxIMaxD(grow_box, d) += grow[d][1];
      }

      /* extend_box - to find the list of potential neighbors, we need to grow
         the local box a bit differently in case, for example, the stencil grows
         in one dimension [0] and not the other [1] */
      hypre_CopyBox(box, extend_box);
      for (d = 0; d < 3; d++)
      { 
         hypre_BoxIMinD(extend_box, d) -= hypre_max(grow[d][0],grow[d][1]);
         hypre_BoxIMaxD(extend_box, d) += hypre_max(grow[d][0],grow[d][1]);
      }

      /*------------------------------------------------
       * Determine the neighbors of box i
       *------------------------------------------------*/
     
      /* Do this by intersecting the extend box with the BoxManager. 
         We must also check for periodic neighbors. */

      neighbor_count = 0;
      hypre_BoxArraySetSize(neighbor_boxes, 0);
      /* shift the box by each period (k=0 is original box) */
      for (k = 0; k < num_periods; k++)
      {
         hypre_CopyBox(extend_box, periodic_box);
         pshift = hypre_StructGridPShift(grid, k);
         hypre_BoxShiftPos(periodic_box, pshift);
         
         /* get the intersections */
         hypre_BoxManIntersect(boxman, hypre_BoxIMin(periodic_box) , 
                               hypre_BoxIMax(periodic_box) , 
                               &entries , &num_entries);
      
         /* note: do we need to remove the intersection with our original box?
            no if periodic, yes if non-periodic (k=0) */ 

         /* unpack entries (first check storage) */
         if (neighbor_count + num_entries > neighbor_alloc)
         {
            neighbor_alloc = neighbor_count + num_entries + 5;
            neighbor_procs = hypre_TReAlloc(neighbor_procs, HYPRE_Int,
                                            neighbor_alloc);
            neighbor_ids = hypre_TReAlloc(neighbor_ids, HYPRE_Int, neighbor_alloc);
            neighbor_shifts = hypre_TReAlloc(neighbor_shifts, HYPRE_Int,
                                             neighbor_alloc);
         }
         /* check storage for the array */
         hypre_BoxArraySetSize(neighbor_boxes, neighbor_count + num_entries);
         /* now unpack */
         for (j = 0; j < num_entries; j++)
         {
            entry = entries[j];
            proc_id = hypre_BoxManEntryProc(entry);        
            id = hypre_BoxManEntryId(entry); 
            /* don't keep box i in the non-periodic case*/  
            if (!k)
            {
               if((myid == proc_id) && (box_id == id))
               {
                  continue;
               }
            }

            hypre_BoxManEntryGetExtents(entry, ilower, iupper);        
            hypre_BoxSetExtents(hypre_BoxArrayBox(neighbor_boxes, neighbor_count),
                                ilower, iupper);
            /* shift the periodic boxes (needs to be the opposite of above) */
            if (k)
            {
               hypre_BoxShiftNeg(
                  hypre_BoxArrayBox(neighbor_boxes, neighbor_count), pshift);
            }
            
            neighbor_procs[neighbor_count] = proc_id;
            neighbor_ids[neighbor_count] = id;
            neighbor_shifts[neighbor_count] = k;
            neighbor_count++;
         }
         hypre_BoxArraySetSize(neighbor_boxes, neighbor_count);

         hypre_TFree(entries);
  
      } /* end of loop through periods k */

      /* Now we have a list of all of the neighbors for box i! */

      /* note: we don't want/need to remove duplicates - they should have
         different intersections (TO DO: put more thought into if there are ever
         any exceptions to this? - the intersection routine already eliminates
         duplicates - so what i mean is eliminating duplicates from multiple
         intersection calls in periodic case)  */  
    
      /*------------------------------------------------
       * Compute recv_box_array for box i
       *------------------------------------------------*/

      /* check size of storage for cboxes */
      /* let's make sure that we have enough storage in case each neighbor
         produces a send/recv region */
      if (neighbor_count > cbox_alloc)
      {
         cbox_alloc = neighbor_count;
         cboxes_neighbor_location = hypre_TReAlloc(cboxes_neighbor_location, 
                                                   HYPRE_Int, cbox_alloc);
         cboxes = hypre_TReAlloc(cboxes, hypre_Box *, cbox_alloc);
         cboxes_mem = hypre_TReAlloc(cboxes_mem, hypre_Box, cbox_alloc);
      }

      /* Loop through each neighbor box.  If the neighbor box intersects the
         grown box i (grown according to our stencil), then the intersection is
         a recv region.  If the neighbor box was shifted to handle periodicity,
         we need to (positive) shift it back. */

      num_cboxes = 0;
      
      for (k = 0; k < neighbor_count; k++)
      {
         hood_box = hypre_BoxArrayBox(neighbor_boxes, k);
         /* check the stencil grid to see if it makes sense to intersect */
         for (d = 0; d < 3; d++)
         {
            sgindex[d] = 1;
               
            s = hypre_BoxIMinD(hood_box, d) - hypre_BoxIMaxD(box, d);
            if (s > 0)
            {
               sgindex[d] = 2;
            }
            s = hypre_BoxIMinD(box, d) - hypre_BoxIMaxD(hood_box, d);
            if (s > 0)
            {
               sgindex[d] = 0;
            }
         }
         /* it makes sense only if we have at least one non-zero entry */   
         if (stencil_grid[sgindex[0]][sgindex[1]][sgindex[2]])
         {
            /* intersect - result is int_box */
            hypre_IntersectBoxes(grow_box, hood_box, int_box);
            /* if we have a positive volume box, this is a recv region */
            if (hypre_BoxVolume(int_box))
            {
               /* keep track of which neighbor: k... */
               cboxes_neighbor_location[num_cboxes] = k;
               cboxes[num_cboxes] = &cboxes_mem[num_cboxes];
               /* keep the intersected box */
               hypre_CopyBox(int_box, cboxes[num_cboxes]);
               num_cboxes++;
            }
         }
      } /* end of loop through each neighbor */

      /* create recv_box_array and recv_procs for box i */
      recv_box_array = hypre_BoxArrayArrayBoxArray(recv_boxes, i);
      hypre_BoxArraySetSize(recv_box_array, num_cboxes);
      recv_procs[i] = hypre_CTAlloc(HYPRE_Int, num_cboxes);
      recv_rboxnums[i] = hypre_CTAlloc(HYPRE_Int, num_cboxes);
      recv_rbox_array = hypre_BoxArrayArrayBoxArray(recv_rboxes, i);
      hypre_BoxArraySetSize(recv_rbox_array, num_cboxes);

      for (m = 0; m < num_cboxes; m++)
      {
         loc = cboxes_neighbor_location[m];
         recv_procs[i][m] = neighbor_procs[loc];
         recv_rboxnums[i][m] = neighbor_ids[loc];
         hypre_CopyBox(cboxes[m], hypre_BoxArrayBox(recv_box_array, m));

         /* if periodic, positive shift before copying to the rbox_array */
         if (neighbor_shifts[loc]) /* periodic if shift != 0 */
         {
            pshift = hypre_StructGridPShift(grid, neighbor_shifts[loc]);
            hypre_BoxShiftPos(cboxes[m], pshift);
         }
         hypre_CopyBox(cboxes[m], hypre_BoxArrayBox(recv_rbox_array, m));

         cboxes[m] = NULL;
      }

      /*------------------------------------------------
       * Compute send_box_array for box i
       *------------------------------------------------*/

      /* Loop through each neighbor box.  If the grown neighbor box intersects
         box i, then the intersection is a send region.  If the neighbor box was
         shifted to handle periodicity, we need to (positive) shift it back. */

      num_cboxes = 0;

      for (k = 0; k < neighbor_count; k++)
      {
         hood_box = hypre_BoxArrayBox(neighbor_boxes, k);
         /* check the stencil grid to see if it makes sense to intersect */
         for (d = 0; d < 3; d++)
         {
            sgindex[d] = 1;
            
            s = hypre_BoxIMinD(box, d) - hypre_BoxIMaxD(hood_box, d);
            if (s > 0)
            {
               sgindex[d] = 2;
            }
            s = hypre_BoxIMinD(hood_box, d) - hypre_BoxIMaxD(box, d);
            if (s > 0)
            {
               sgindex[d] = 0;
            }
         }
         /* it makes sense only if we have at least one non-zero entry */   
         if (stencil_grid[sgindex[0]][sgindex[1]][sgindex[2]])
         {
            /* grow the neighbor box and intersect */
            hypre_CopyBox(hood_box, grow_box);
            for (d = 0; d < 3; d++)
            {
               hypre_BoxIMinD(grow_box, d) -= grow[d][0];
               hypre_BoxIMaxD(grow_box, d) += grow[d][1];
            }
            hypre_IntersectBoxes(box, grow_box, int_box);
            /* if we have a positive volume box, this is a send region */
            if (hypre_BoxVolume(int_box))
            {
               /* keep track of which neighbor: k... */
               cboxes_neighbor_location[num_cboxes] = k;
               cboxes[num_cboxes] = &cboxes_mem[num_cboxes];
               /* keep the intersected box */
               hypre_CopyBox(int_box, cboxes[num_cboxes]);
               num_cboxes++;
            }
         }
      }/* end of loop through neighbors */

      /* create send_box_array and send_procs for box i */
      send_box_array = hypre_BoxArrayArrayBoxArray(send_boxes, i);
      hypre_BoxArraySetSize(send_box_array, num_cboxes);
      send_procs[i] = hypre_CTAlloc(HYPRE_Int, num_cboxes);
      send_rboxnums[i] = hypre_CTAlloc(HYPRE_Int, num_cboxes);
      send_rbox_array = hypre_BoxArrayArrayBoxArray(send_rboxes, i);
      hypre_BoxArraySetSize(send_rbox_array, num_cboxes);

      for (m = 0; m < num_cboxes; m++)
      {
         loc = cboxes_neighbor_location[m];
         send_procs[i][m] = neighbor_procs[loc];
         send_rboxnums[i][m] = neighbor_ids[loc];
         hypre_CopyBox(cboxes[m], hypre_BoxArrayBox(send_box_array, m));

         /* if periodic, positive shift before copying to the rbox_array */
         if (neighbor_shifts[loc]) /* periodic if shift != 0 */
         {
            pshift = hypre_StructGridPShift(grid, neighbor_shifts[loc]);
            hypre_BoxShiftPos(cboxes[m], pshift);
         }
         hypre_CopyBox(cboxes[m], hypre_BoxArrayBox(send_rbox_array, m));

         cboxes[m] = NULL;
      }
   } /* end of loop through each local box */