/* Implementation of the MATMUL intrinsic
   Copyright 2002 Free Software Foundation, Inc.
   Contributed by Paul Brook <paul@nowt.org>

This file is part of the GNU Fortran 95 runtime library (libgfortran).

Libgfortran is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

Libgfortran 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
GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with libgfor; see the file COPYING.LIB.  If not,
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

#include "config.h"
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include "libgfortran.h"

/* This is a C version of the following fortran pseudo-code. The key
   point is the loop order -- we access all arrays column-first, which
   improves the performance enough to boost galgel spec score by 50%.

   DIMENSION A(M,COUNT), B(COUNT,N), C(M,N)
   C = 0
   DO J=1,N
     DO K=1,COUNT
       DO I=1,M
         C(I,J) = C(I,J)+A(I,K)*B(K,J)
*/

extern void matmul_r4 (gfc_array_r4 * retarray, gfc_array_r4 * a, gfc_array_r4 * b);
export_proto(matmul_r4);

void
matmul_r4 (gfc_array_r4 * retarray, gfc_array_r4 * a, gfc_array_r4 * b)
{
  GFC_REAL_4 *abase;
  GFC_REAL_4 *bbase;
  GFC_REAL_4 *dest;

  index_type rxstride, rystride, axstride, aystride, bxstride, bystride;
  index_type x, y, n, count, xcount, ycount;

  assert (GFC_DESCRIPTOR_RANK (a) == 2
          || GFC_DESCRIPTOR_RANK (b) == 2);

/* C[xcount,ycount] = A[xcount, count] * B[count,ycount]

   Either A or B (but not both) can be rank 1:

   o One-dimensional argument A is implicitly treated as a row matrix
     dimensioned [1,count], so xcount=1.

   o One-dimensional argument B is implicitly treated as a column matrix
     dimensioned [count, 1], so ycount=1.
  */

  if (retarray->data == NULL)
    {
      if (GFC_DESCRIPTOR_RANK (a) == 1)
        {
          retarray->dim[0].lbound = 0;
          retarray->dim[0].ubound = b->dim[1].ubound - b->dim[1].lbound;
          retarray->dim[0].stride = 1;
        }
      else if (GFC_DESCRIPTOR_RANK (b) == 1)
        {
          retarray->dim[0].lbound = 0;
          retarray->dim[0].ubound = a->dim[0].ubound - a->dim[0].lbound;
          retarray->dim[0].stride = 1;
        }
      else
        {
          retarray->dim[0].lbound = 0;
          retarray->dim[0].ubound = a->dim[0].ubound - a->dim[0].lbound;
          retarray->dim[0].stride = 1;
          
          retarray->dim[1].lbound = 0;
          retarray->dim[1].ubound = b->dim[1].ubound - b->dim[1].lbound;
          retarray->dim[1].stride = retarray->dim[0].ubound+1;
        }
          
      retarray->data
	= internal_malloc_size (sizeof (GFC_REAL_4) * size0 (retarray));
      retarray->base = 0;
    }

  abase = a->data;
  bbase = b->data;
  dest = retarray->data;

  if (retarray->dim[0].stride == 0)
    retarray->dim[0].stride = 1;
  if (a->dim[0].stride == 0)
    a->dim[0].stride = 1;
  if (b->dim[0].stride == 0)
    b->dim[0].stride = 1;


  if (GFC_DESCRIPTOR_RANK (retarray) == 1)
    {
      /* One-dimensional result may be addressed in the code below
	 either as a row or a column matrix. We want both cases to
	 work. */
      rxstride = rystride = retarray->dim[0].stride;
    }
  else
    {
      rxstride = retarray->dim[0].stride;
      rystride = retarray->dim[1].stride;
    }


  if (GFC_DESCRIPTOR_RANK (a) == 1)
    {
      /* Treat it as a a row matrix A[1,count]. */
      axstride = a->dim[0].stride;
      aystride = 1;

      xcount = 1;
      count = a->dim[0].ubound + 1 - a->dim[0].lbound;
    }
  else
    {
      axstride = a->dim[0].stride;
      aystride = a->dim[1].stride;

      count = a->dim[1].ubound + 1 - a->dim[1].lbound;
      xcount = a->dim[0].ubound + 1 - a->dim[0].lbound;
    }

  assert(count == b->dim[0].ubound + 1 - b->dim[0].lbound);

  if (GFC_DESCRIPTOR_RANK (b) == 1)
    {
      /* Treat it as a column matrix B[count,1] */
      bxstride = b->dim[0].stride;

      /* bystride should never be used for 1-dimensional b.
	 in case it is we want it to cause a segfault, rather than
	 an incorrect result. */
      bystride = 0xDEADBEEF; 
      ycount = 1;
    }
  else
    {
      bxstride = b->dim[0].stride;
      bystride = b->dim[1].stride;
      ycount = b->dim[1].ubound + 1 - b->dim[1].lbound;
    }

  assert (a->base == 0);
  assert (b->base == 0);
  assert (retarray->base == 0);

  abase = a->data;
  bbase = b->data;
  dest = retarray->data;

  if (rxstride == 1 && axstride == 1 && bxstride == 1)
    {
      GFC_REAL_4 *bbase_y;
      GFC_REAL_4 *dest_y;
      GFC_REAL_4 *abase_n;
      GFC_REAL_4 bbase_yn;

      memset (dest, 0, (sizeof (GFC_REAL_4) * size0(retarray)));

      for (y = 0; y < ycount; y++)
	{
	  bbase_y = bbase + y*bystride;
	  dest_y = dest + y*rystride;
	  for (n = 0; n < count; n++)
	    {
	      abase_n = abase + n*aystride;
	      bbase_yn = bbase_y[n];
	      for (x = 0; x < xcount; x++)
		{
		  dest_y[x] += abase_n[x] * bbase_yn;
		}
	    }
	}
    }
  else
    {
      for (y = 0; y < ycount; y++)
	for (x = 0; x < xcount; x++)
	  dest[x*rxstride + y*rystride] = (GFC_REAL_4)0;

      for (y = 0; y < ycount; y++)
	for (n = 0; n < count; n++)
	  for (x = 0; x < xcount; x++)
	    /* dest[x,y] += a[x,n] * b[n,y] */
	    dest[x*rxstride + y*rystride] += abase[x*axstride + n*aystride] * bbase[n*bxstride + y*bystride];
    }
}