| // This file is part of Eigen, a lightweight C++ template library |
| // for linear algebra. |
| // |
| // Copyright (C) 2010 Gael Guennebaud <gael.guennebaud@inria.fr> |
| // |
| // This Source Code Form is subject to the terms of the Mozilla |
| // Public License v. 2.0. If a copy of the MPL was not distributed |
| // with this file, You can obtain one at http://mozilla.org/MPL/2.0/. |
| |
| #ifndef EIGEN_PARALLELIZER_H |
| #define EIGEN_PARALLELIZER_H |
| |
| // IWYU pragma: private |
| #include "../InternalHeaderCheck.h" |
| |
| namespace Eigen { |
| |
| namespace internal { |
| |
| /** \internal */ |
| inline void manage_multi_threading(Action action, int* v) |
| { |
| static int m_maxThreads = -1; |
| EIGEN_UNUSED_VARIABLE(m_maxThreads) |
| |
| 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); |
| } |
| } |
| |
| } |
| |
| /** Must be call first when calling Eigen from multiple threads */ |
| inline void initParallel() |
| { |
| int nbt; |
| internal::manage_multi_threading(GetAction, &nbt); |
| std::ptrdiff_t l1, l2, l3; |
| internal::manage_caching_sizes(GetAction, &l1, &l2, &l3); |
| } |
| |
| /** \returns the max number of threads reserved for Eigen |
| * \sa setNbThreads */ |
| inline int nbThreads() |
| { |
| int ret; |
| internal::manage_multi_threading(GetAction, &ret); |
| return ret; |
| } |
| |
| /** Sets the max number of threads reserved for Eigen |
| * \sa nbThreads */ |
| inline void setNbThreads(int v) |
| { |
| internal::manage_multi_threading(SetAction, &v); |
| } |
| |
| namespace internal { |
| |
| template<typename Index> struct GemmParallelInfo |
| { |
| |
| #ifdef EIGEN_HAS_OPENMP |
| GemmParallelInfo() : sync(-1), users(0), lhs_start(0), lhs_length(0) {} |
| std::atomic<Index> sync; |
| std::atomic<int> users; |
| #else |
| GemmParallelInfo() : lhs_start(0), lhs_length(0) {} |
| #endif |
| |
| Index lhs_start; |
| Index lhs_length; |
| }; |
| |
| template<bool Condition, typename Functor, typename Index> |
| void parallelize_gemm(const Functor& func, Index rows, Index cols, Index depth, bool transpose) |
| { |
| // TODO when EIGEN_USE_BLAS is defined, |
| // we should still enable OMP for other scalar types |
| // Without C++11, we have to disable GEMM's parallelization on |
| // non x86 architectures because there volatile is not enough for our purpose. |
| // See bug 1572. |
| #if (! defined(EIGEN_HAS_OPENMP)) || defined(EIGEN_USE_BLAS) |
| // 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 redesigned anyway. |
| EIGEN_UNUSED_VARIABLE(depth); |
| 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 |
| |
| // compute the maximal number of threads from the size of the product: |
| // This first heuristic takes into account that the product kernel is fully optimized when working with nr columns at once. |
| Index size = transpose ? rows : cols; |
| Index pb_max_threads = std::max<Index>(1,size / Functor::Traits::nr); |
| |
| // compute the maximal number of threads from the total amount of work: |
| double work = static_cast<double>(rows) * static_cast<double>(cols) * |
| static_cast<double>(depth); |
| double kMinTaskSize = 50000; // FIXME improve this heuristic. |
| pb_max_threads = std::max<Index>(1, std::min<Index>(pb_max_threads, static_cast<Index>( work / kMinTaskSize ) )); |
| |
| // compute the number of threads we are going to use |
| Index threads = std::min<Index>(nbThreads(), pb_max_threads); |
| |
| // if multi-threading is explicitly disabled, not useful, or if we already are in a parallel session, |
| // then abort multi-threading |
| // FIXME omp_get_num_threads()>1 only works for openmp, what if the user does not use openmp? |
| if((!Condition) || (threads==1) || (omp_get_num_threads()>1)) |
| return func(0,rows, 0,cols); |
| |
| Eigen::initParallel(); |
| func.initParallelSession(threads); |
| |
| if(transpose) |
| std::swap(rows,cols); |
| |
| ei_declare_aligned_stack_constructed_variable(GemmParallelInfo<Index>,info,threads,0); |
| |
| #pragma omp parallel num_threads(threads) |
| { |
| Index i = omp_get_thread_num(); |
| // Note that the actual number of threads might be lower than the number of request ones. |
| Index actual_threads = omp_get_num_threads(); |
| |
| Index blockCols = (cols / actual_threads) & ~Index(0x3); |
| Index blockRows = (rows / actual_threads); |
| blockRows = (blockRows/Functor::Traits::mr)*Functor::Traits::mr; |
| |
| Index r0 = i*blockRows; |
| Index actualBlockRows = (i+1==actual_threads) ? rows-r0 : blockRows; |
| |
| Index c0 = i*blockCols; |
| Index actualBlockCols = (i+1==actual_threads) ? cols-c0 : blockCols; |
| |
| info[i].lhs_start = r0; |
| info[i].lhs_length = actualBlockRows; |
| |
| if(transpose) func(c0, actualBlockCols, 0, rows, info); |
| else func(0, rows, c0, actualBlockCols, info); |
| } |
| #endif |
| } |
| |
| } // end namespace internal |
| |
| } // end namespace Eigen |
| |
| #endif // EIGEN_PARALLELIZER_H |