/*BHEADER**********************************************************************
 * Copyright (c) 2006   The Regents of the University of California.
 * Produced at the Lawrence Livermore National Laboratory.
 * Written by the HYPRE team. UCRL-CODE-222953.
 * All rights reserved.
 *
 * This file is part of HYPRE (see http://www.llnl.gov/CASC/hypre/).
 * Please see the COPYRIGHT_and_LICENSE file for the copyright notice, 
 * disclaimer, contact information and the GNU Lesser General Public License.
 *
 * HYPRE is free software; you can redistribute it and/or modify it under the 
 * terms of the GNU General Public License (as published by the Free Software
 * Foundation) version 2.1 dated February 1999.
 *
 * HYPRE is distributed in the hope that it will be useful, but WITHOUT ANY 
 * WARRANTY; without even the IMPLIED WARRANTY OF MERCHANTABILITY or FITNESS 
 * FOR A PARTICULAR PURPOSE.  See the terms and conditions of the GNU General
 * Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 * $Revision: 2.8 $
 ***********************************************************************EHEADER*/


/******************************************************************************
 *
 * Relaxation scheme
 *
 *****************************************************************************/

#include "headers.h"
//#include "omp.h"

/*--------------------------------------------------------------------------
 * hypre_BoomerAMGSeqRelax
 *--------------------------------------------------------------------------*/

int  hypre_BoomerAMGSeqRelax( hypre_CSRMatrix *A,
                        hypre_Vector    *f,
                        hypre_Vector    *u)
{
   double         *A_diag_data  = hypre_CSRMatrixData(A);
   int            *A_diag_i     = hypre_CSRMatrixI(A);
   int            *A_diag_j     = hypre_CSRMatrixJ(A);

   int             n       = hypre_CSRMatrixNumRows(A);
   
   double         *u_data  = hypre_VectorData(u);

   double         *f_data  = hypre_VectorData(f);

   double         *tmp_data;
   
   double          res;

   
   int             i, j;
   int             ii, jj;
   int             ns, ne, size, rest;
   int             relax_error = 0;
   //   int		   index, start;
   int		   num_threads;

   num_threads = hypre_NumThreads();
   /*-----------------------------------------------------------------------
    * Switch statement to direct control based on relax_type:
    *     relax_type = 3 -> hybrid: SOR-J mix off-processor, SOR on-processor
    *     		    with outer relaxation parameters (forward solve)
    *-----------------------------------------------------------------------*/

        /*-----------------------------------------------------------------
         * Relax all points.
         *-----------------------------------------------------------------*/

        if (1)
          {
	   tmp_data = hypre_CTAlloc(double,n);
#pragma omp parallel private(num_threads)
 {
            num_threads = 1; /* omp_get_num_threads(); */

#pragma omp for private(i)
           for (i = 0; i < n; i++)
	      tmp_data[i] = u_data[i];

#pragma omp for  private(i,ii,j,jj,ns,ne,res,rest,size)
           for (j = 0; j < num_threads; j++)
	   {
	    size = n/num_threads;
	    rest = n - size*num_threads;
	    if (j < rest)
	    {
	       ns = j*size+j;
	       ne = (j+1)*size+j+1;
	    }
	    else
	    {
	       ns = j*size+rest;
	       ne = (j+1)*size+rest;
	    }
            for (i = ns; i < ne; i++)	/* interior points first */
            {

               /*-----------------------------------------------------------
                * If diagonal is nonzero, relax point i; otherwise, skip it.
                *-----------------------------------------------------------*/
             
               if ( A_diag_data[A_diag_i[i]] != 0.0)
               {
                  res = f_data[i];
                  for (jj = A_diag_i[i]+1; jj < A_diag_i[i+1]; jj++)
                  {
                     ii = A_diag_j[jj];
		     if (ii >= ns && ii < ne)
                        res -= A_diag_data[jj] * u_data[ii];
		     else
                        res -= A_diag_data[jj] * tmp_data[ii];
                  }
                  u_data[i] = res / A_diag_data[A_diag_i[i]];
               }
            }
           }
 }
           hypre_TFree(tmp_data);
          }
	  else
          {
            for (i = 0; i < n; i++)	/* interior points first */
            {

               /*-----------------------------------------------------------
                * If diagonal is nonzero, relax point i; otherwise, skip it.
                *-----------------------------------------------------------*/
             
               if ( A_diag_data[A_diag_i[i]] != 0.0)
               {
                  res = f_data[i];
                  for (jj = A_diag_i[i]+1; jj < A_diag_i[i+1]; jj++)
                  {
                     ii = A_diag_j[jj];
                     res -= A_diag_data[jj] * u_data[ii];
                  }
                  u_data[i] = res / A_diag_data[A_diag_i[i]];
               }
            }
          }

   return(relax_error); 
}