path: root/Eigen/src/Core/CacheFriendlyProduct.h

// This file is part of Eigen, a lightweight C++ template library
// for linear algebra. Eigen itself is part of the KDE project.
//
// Copyright (C) 2008 Gael Guennebaud <g.gael@free.fr>
//
// Eigen 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 3 of the License, or (at your option) any later version.
//
// Alternatively, you can redistribute it and/or
// modify it under the terms of the GNU General Public License as
// published by the Free Software Foundation; either version 2 of
// the License, or (at your option) any later version.
//
// Eigen 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 or the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License and a copy of the GNU General Public License along with
// Eigen. If not, see <http://www.gnu.org/licenses/>.

#ifndef EIGEN_CACHE_FRIENDLY_PRODUCT_H
#define EIGEN_CACHE_FRIENDLY_PRODUCT_H

template<typename Scalar>
static void ei_cache_friendly_product(
  int _rows, int _cols, int depth,
  bool _lhsRowMajor, const Scalar* _lhs, int _lhsStride,
  bool _rhsRowMajor, const Scalar* _rhs, int _rhsStride,
  bool resRowMajor, Scalar* res, int resStride)
{
  const Scalar* __restrict__ lhs;
  const Scalar* __restrict__ rhs;
  int lhsStride, rhsStride, rows, cols;
  bool lhsRowMajor;

  if (resRowMajor)
  {
    lhs = _rhs;
    rhs = _lhs;
    lhsStride = _rhsStride;
    rhsStride = _lhsStride;
    cols = _rows;
    rows = _cols;
    lhsRowMajor = !_rhsRowMajor;
    ei_assert(_lhsRowMajor);
  }
  else
  {
    lhs = _lhs;
    rhs = _rhs;
    lhsStride = _lhsStride;
    rhsStride = _rhsStride;
    rows = _rows;
    cols = _cols;
    lhsRowMajor = _lhsRowMajor;
    ei_assert(!_rhsRowMajor);
  }

  typedef typename ei_packet_traits<Scalar>::type PacketType;

  enum {
    PacketSize = sizeof(PacketType)/sizeof(Scalar),
    #if (defined __i386__)
    // i386 architecture provides only 8 xmm registers,
    // so let's reduce the max number of rows processed at once.
    MaxBlockRows = 4,
    MaxBlockRows_ClampingMask = 0xFFFFFC,
    #else
    MaxBlockRows = 8,
    MaxBlockRows_ClampingMask = 0xFFFFF8,
    #endif
    // maximal size of the blocks fitted in L2 cache
    MaxL2BlockSize = EIGEN_TUNE_FOR_L2_CACHE_SIZE / sizeof(Scalar)
  };


  //const bool rhsIsAligned = (PacketSize==1) || (((rhsStride%PacketSize) == 0) && (size_t(rhs)%16==0));
  const bool resIsAligned = (PacketSize==1) || (((resStride%PacketSize) == 0) && (size_t(res)%16==0));

  const int remainingSize = depth % PacketSize;
  const int size = depth - remainingSize; // third dimension of the product clamped to packet boundaries
  const int l2BlockRows = MaxL2BlockSize > rows ? rows : MaxL2BlockSize;
  const int l2BlockCols = MaxL2BlockSize > cols ? cols : MaxL2BlockSize;
  const int l2BlockSize = MaxL2BlockSize > size ? size : MaxL2BlockSize;
  Scalar* __restrict__ block = 0;
  const int allocBlockSize = sizeof(Scalar)*l2BlockRows*size;
  if (allocBlockSize>16000000)
    block = (Scalar*)malloc(allocBlockSize);
  else
    block = (Scalar*)alloca(allocBlockSize);
  Scalar* __restrict__ rhsCopy = (Scalar*)alloca(sizeof(Scalar)*l2BlockSize);

  // loops on each L2 cache friendly blocks of the result
  for(int l2i=0; l2i<rows; l2i+=l2BlockRows)
  {
    const int l2blockRowEnd = std::min(l2i+l2BlockRows, rows);
    const int l2blockRowEndBW = l2blockRowEnd & MaxBlockRows_ClampingMask;    // end of the rows aligned to bw
    const int l2blockRemainingRows = l2blockRowEnd - l2blockRowEndBW;         // number of remaining rows
    //const int l2blockRowEndBWPlusOne = l2blockRowEndBW + (l2blockRemainingRows?0:MaxBlockRows);

    // build a cache friendly blocky matrix
    int count = 0;

    // copy l2blocksize rows of m_lhs to blocks of ps x bw
    asm("#eigen begin buildblocks");
    for(int l2k=0; l2k<size; l2k+=l2BlockSize)
    {
      const int l2blockSizeEnd = std::min(l2k+l2BlockSize, size);

      for (int i = l2i; i<l2blockRowEndBW/*PlusOne*/; i+=MaxBlockRows)
      {
        // TODO merge the if l2blockRemainingRows
//         const int blockRows = std::min(i+MaxBlockRows, rows) - i;

        for (int k=l2k; k<l2blockSizeEnd; k+=PacketSize)
        {
          // TODO write these loops using meta unrolling
          // negligible for large matrices but useful for small ones
          if (lhsRowMajor)
          {
            for (int w=0; w<MaxBlockRows; ++w)
              for (int s=0; s<PacketSize; ++s)
                block[count++] = lhs[(i+w)*lhsStride + (k+s)];
          }
          else
          {
            for (int w=0; w<MaxBlockRows; ++w)
              for (int s=0; s<PacketSize; ++s)
                block[count++] = lhs[(i+w) + (k+s)*lhsStride];
          }
        }
      }
      if (l2blockRemainingRows>0)
      {
        for (int k=l2k; k<l2blockSizeEnd; k+=PacketSize)
        {
          if (lhsRowMajor)
          {
            for (int w=0; w<l2blockRemainingRows; ++w)
              for (int s=0; s<PacketSize; ++s)
                block[count++] = lhs[(l2blockRowEndBW+w)*lhsStride + (k+s)];
          }
          else
          {
            for (int w=0; w<l2blockRemainingRows; ++w)
              for (int s=0; s<PacketSize; ++s)
                block[count++] = lhs[(l2blockRowEndBW+w) + (k+s)*lhsStride];
          }
        }
      }
    }
    asm("#eigen end buildblocks");

    for(int l2j=0; l2j<cols; l2j+=l2BlockCols)
    {
      int l2blockColEnd = std::min(l2j+l2BlockCols, cols);

      for(int l2k=0; l2k<size; l2k+=l2BlockSize)
      {
        // acumulate bw rows of lhs time a single column of rhs to a bw x 1 block of res
        int l2blockSizeEnd = std::min(l2k+l2BlockSize, size);

        // for each bw x 1 result's block
        for(int l1i=l2i; l1i<l2blockRowEndBW; l1i+=MaxBlockRows)
        {
          for(int l1j=l2j; l1j<l2blockColEnd; l1j+=1)
          {
            int offsetblock = l2k * (l2blockRowEnd-l2i) + (l1i-l2i)*(l2blockSizeEnd-l2k) - l2k*MaxBlockRows;
            const Scalar* __restrict__ localB = &block[offsetblock];

            const Scalar* __restrict__ rhsColumn = &(rhs[l1j*rhsStride]);

            // copy unaligned rhs data
            // YES it seems to be faster to copy some part of rhs multiple times
            // to aligned memory rather than using unligned load.
            // Moreover this avoids a "if" in the most nested loop :)
            if (PacketSize>1 && size_t(rhsColumn)%16)
            {
              int count = 0;
              for (int k = l2k; k<l2blockSizeEnd; ++k)
              {
                rhsCopy[count++] = rhsColumn[k];
              }
              rhsColumn = &(rhsCopy[-l2k]);
            }

            PacketType dst[MaxBlockRows];
            dst[0] = ei_pset1(Scalar(0.));
            dst[1] = dst[0];
            dst[2] = dst[0];
            dst[3] = dst[0];
            if (MaxBlockRows==8)
            {
              dst[4] = dst[0];
              dst[5] = dst[0];
              dst[6] = dst[0];
              dst[7] = dst[0];
            }

            PacketType tmp;

            asm("#eigen begincore");
            for(int k=l2k; k<l2blockSizeEnd; k+=PacketSize)
            {
              tmp = ei_pload(&rhsColumn[k]);

              dst[0] = ei_pmadd(tmp, ei_pload(&(localB[k*MaxBlockRows             ])), dst[0]);
              dst[1] = ei_pmadd(tmp, ei_pload(&(localB[k*MaxBlockRows+  PacketSize])), dst[1]);
              dst[2] = ei_pmadd(tmp, ei_pload(&(localB[k*MaxBlockRows+2*PacketSize])), dst[2]);
              dst[3] = ei_pmadd(tmp, ei_pload(&(localB[k*MaxBlockRows+3*PacketSize])), dst[3]);
              if (MaxBlockRows==8)
              {
                dst[4] = ei_pmadd(tmp, ei_pload(&(localB[k*MaxBlockRows+4*PacketSize])), dst[4]);
                dst[5] = ei_pmadd(tmp, ei_pload(&(localB[k*MaxBlockRows+5*PacketSize])), dst[5]);
                dst[6] = ei_pmadd(tmp, ei_pload(&(localB[k*MaxBlockRows+6*PacketSize])), dst[6]);
                dst[7] = ei_pmadd(tmp, ei_pload(&(localB[k*MaxBlockRows+7*PacketSize])), dst[7]);
              }
            }

            Scalar* __restrict__ localRes = &(res[l1i + l1j*resStride]);

            if (PacketSize>1 && resIsAligned)
            {
              ei_pstore(&(localRes[0]), ei_padd(ei_pload(&(localRes[0])), ei_preduxp(dst)));
              if (PacketSize==2)
                ei_pstore(&(localRes[2]), ei_padd(ei_pload(&(localRes[2])), ei_preduxp(&(dst[2]))));
              if (MaxBlockRows==8)
              {
                ei_pstore(&(localRes[4]), ei_padd(ei_pload(&(localRes[4])), ei_preduxp(&(dst[4]))));
                if (PacketSize==2)
                  ei_pstore(&(localRes[6]), ei_padd(ei_pload(&(localRes[6])), ei_preduxp(&(dst[6]))));
              }
            }
            else
            {
              localRes[0] += ei_predux(dst[0]);
              localRes[1] += ei_predux(dst[1]);
              localRes[2] += ei_predux(dst[2]);
              localRes[3] += ei_predux(dst[3]);
              if (MaxBlockRows==8)
              {
                localRes[4] += ei_predux(dst[4]);
                localRes[5] += ei_predux(dst[5]);
                localRes[6] += ei_predux(dst[6]);
                localRes[7] += ei_predux(dst[7]);
              }
            }
            asm("#eigen endcore");
          }
        }
        if (l2blockRemainingRows>0)
        {
          int offsetblock = l2k * (l2blockRowEnd-l2i) + (l2blockRowEndBW-l2i)*(l2blockSizeEnd-l2k) - l2k*l2blockRemainingRows;
          const Scalar* localB = &block[offsetblock];

          asm("#eigen begin dynkernel");
          for(int l1j=l2j; l1j<l2blockColEnd; l1j+=1)
          {
            const Scalar* __restrict__ rhsColumn = &(rhs[l1j*rhsStride]);

            // copy unaligned rhs data
            if (PacketSize>1 && size_t(rhsColumn)%16)
            {
              int count = 0;
              for (int k = l2k; k<l2blockSizeEnd; ++k)
              {
                rhsCopy[count++] = rhsColumn[k];
              }
              rhsColumn = &(rhsCopy[-l2k]);
            }

            PacketType dst[MaxBlockRows];
            dst[0] = ei_pset1(Scalar(0.));
            dst[1] = dst[0];
            dst[2] = dst[0];
            dst[3] = dst[0];
            if (MaxBlockRows>4)
            {
              dst[4] = dst[0];
              dst[5] = dst[0];
              dst[6] = dst[0];
              dst[7] = dst[0];
            }

            // let's declare a few other temporary registers
            PacketType tmp;

            for(int k=l2k; k<l2blockSizeEnd; k+=PacketSize)
            {
              tmp = ei_pload(&rhsColumn[k]);

                                           dst[0] = ei_pmadd(tmp, ei_pload(&(localB[k*l2blockRemainingRows             ])), dst[0]);
              if (l2blockRemainingRows>=2) dst[1] = ei_pmadd(tmp, ei_pload(&(localB[k*l2blockRemainingRows+  PacketSize])), dst[1]);
              if (l2blockRemainingRows>=3) dst[2] = ei_pmadd(tmp, ei_pload(&(localB[k*l2blockRemainingRows+2*PacketSize])), dst[2]);
              if (l2blockRemainingRows>=4) dst[3] = ei_pmadd(tmp, ei_pload(&(localB[k*l2blockRemainingRows+3*PacketSize])), dst[3]);
              if (MaxBlockRows>4)
              {
                if (l2blockRemainingRows>=5) dst[4] = ei_pmadd(tmp, ei_pload(&(localB[k*l2blockRemainingRows+4*PacketSize])), dst[4]);
                if (l2blockRemainingRows>=6) dst[5] = ei_pmadd(tmp, ei_pload(&(localB[k*l2blockRemainingRows+5*PacketSize])), dst[5]);
                if (l2blockRemainingRows>=7) dst[6] = ei_pmadd(tmp, ei_pload(&(localB[k*l2blockRemainingRows+6*PacketSize])), dst[6]);
                if (l2blockRemainingRows>=8) dst[7] = ei_pmadd(tmp, ei_pload(&(localB[k*l2blockRemainingRows+7*PacketSize])), dst[7]);
              }
            }

            Scalar* __restrict__ localRes = &(res[l2blockRowEndBW + l1j*resStride]);

            // process the remaining rows once at a time
                                         localRes[0] += ei_predux(dst[0]);
            if (l2blockRemainingRows>=2) localRes[1] += ei_predux(dst[1]);
            if (l2blockRemainingRows>=3) localRes[2] += ei_predux(dst[2]);
            if (l2blockRemainingRows>=4) localRes[3] += ei_predux(dst[3]);
            if (MaxBlockRows>4)
            {
              if (l2blockRemainingRows>=5) localRes[4] += ei_predux(dst[4]);
              if (l2blockRemainingRows>=6) localRes[5] += ei_predux(dst[5]);
              if (l2blockRemainingRows>=7) localRes[6] += ei_predux(dst[6]);
              if (l2blockRemainingRows>=8) localRes[7] += ei_predux(dst[7]);
            }

            asm("#eigen end dynkernel");
          }
        }
      }
    }
  }
  if (PacketSize>1 && remainingSize)
  {
    if (lhsRowMajor)
    {
      for (int j=0; j<cols; ++j)
        for (int i=0; i<rows; ++i)
        {
          Scalar tmp = lhs[i*lhsStride+size] * rhs[j*rhsStride+size];
          for (int k=1; k<remainingSize; ++k)
            tmp += lhs[i*lhsStride+size+k] * rhs[j*rhsStride+size+k];
          res[i+j*resStride] += tmp;
        }
    }
    else
    {
      for (int j=0; j<cols; ++j)
        for (int i=0; i<rows; ++i)
        {
          Scalar tmp = lhs[i+size*lhsStride] * rhs[j*rhsStride+size];
          for (int k=1; k<remainingSize; ++k)
            tmp += lhs[i+(size+k)*lhsStride] * rhs[j*rhsStride+size+k];
          res[i+j*resStride] += tmp;
        }
    }
  }

  if (allocBlockSize>16000000)
    free(block);
}

#endif // EIGEN_CACHE_FRIENDLY_PRODUCT_H