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// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2010 Gael Guennebaud <gael.guennebaud@inria.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_PARALLELIZER_H
#define EIGEN_PARALLELIZER_H
namespace internal {
/** \internal */
inline void manage_multi_threading(Action action, int* v)
{
static EIGEN_UNUSED int m_maxThreads = -1;
if(action==SetAction)
{
eigen_internal_assert(v!=0);
m_maxThreads = *v;
}
else if(action==GetAction)
{
eigen_internal_assert(v!=0);
#ifdef EIGEN_HAS_OPENMP
if(m_maxThreads>0)
*v = m_maxThreads;
else
*v = omp_get_max_threads();
#else
*v = 1;
#endif
}
else
{
eigen_internal_assert(false);
}
}
/** \returns the max number of threads reserved for Eigen
* \sa setNbThreads */
inline int nbThreads()
{
int ret;
manage_multi_threading(GetAction, &ret);
return ret;
}
/** Sets the max number of threads reserved for Eigen
* \sa nbThreads */
inline void setNbThreads(int v)
{
manage_multi_threading(SetAction, &v);
}
template<typename Index> struct GemmParallelInfo
{
GemmParallelInfo() : sync(-1), users(0), rhs_start(0), rhs_length(0) {}
int volatile sync;
int volatile users;
Index rhs_start;
Index rhs_length;
};
template<bool Condition, typename Functor, typename Index>
void parallelize_gemm(const Functor& func, Index rows, Index cols, bool transpose)
{
#if !(defined (EIGEN_HAS_OPENMP)) || defined (EIGEN_MKL)
// FIXME the transpose variable is only needed to properly split
// the matrix product when multithreading is enabled. This is a temporary
// fix to support row-major destination matrices. This whole
// parallelizer mechanism has to be redisigned anyway.
EIGEN_UNUSED_VARIABLE(transpose);
func(0,rows, 0,cols);
#else
// Dynamically check whether we should enable or disable OpenMP.
// The conditions are:
// - the max number of threads we can create is greater than 1
// - we are not already in a parallel code
// - the sizes are large enough
// 1- are we already in a parallel session?
// FIXME omp_get_num_threads()>1 only works for openmp, what if the user does not use openmp?
if((!Condition) || (omp_get_num_threads()>1))
return func(0,rows, 0,cols);
Index size = transpose ? cols : rows;
// 2- compute the maximal number of threads from the size of the product:
// FIXME this has to be fine tuned
Index max_threads = std::max<Index>(1,size / 32);
// 3 - compute the number of threads we are going to use
Index threads = std::min<Index>(nbThreads(), max_threads);
if(threads==1)
return func(0,rows, 0,cols);
func.initParallelSession();
if(transpose)
std::swap(rows,cols);
Index blockCols = (cols / threads) & ~Index(0x3);
Index blockRows = (rows / threads) & ~Index(0x7);
GemmParallelInfo<Index>* info = new GemmParallelInfo<Index>[threads];
#pragma omp parallel for schedule(static,1) num_threads(threads)
for(Index i=0; i<threads; ++i)
{
Index r0 = i*blockRows;
Index actualBlockRows = (i+1==threads) ? rows-r0 : blockRows;
Index c0 = i*blockCols;
Index actualBlockCols = (i+1==threads) ? cols-c0 : blockCols;
info[i].rhs_start = c0;
info[i].rhs_length = actualBlockCols;
if(transpose)
func(0, cols, r0, actualBlockRows, info);
else
func(r0, actualBlockRows, 0,cols, info);
}
delete[] info;
#endif
}
} // end namespace internal
#endif // EIGEN_PARALLELIZER_H
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