1 // This file is part of Eigen, a lightweight C++ template library 2 // for linear algebra. 3 // 4 // Copyright (C) 2010 Gael Guennebaud <gael.guennebaud (at) inria.fr> 5 // 6 // This Source Code Form is subject to the terms of the Mozilla 7 // Public License v. 2.0. If a copy of the MPL was not distributed 8 // with this file, You can obtain one at http://mozilla.org/MPL/2.0/. 9 10 #ifndef EIGEN_PARALLELIZER_H 11 #define EIGEN_PARALLELIZER_H 12 13 namespace Eigen { 14 15 namespace internal { 16 17 /** \internal */ 18 inline void manage_multi_threading(Action action, int* v) 19 { 20 static EIGEN_UNUSED int m_maxThreads = -1; 21 22 if(action==SetAction) 23 { 24 eigen_internal_assert(v!=0); 25 m_maxThreads = *v; 26 } 27 else if(action==GetAction) 28 { 29 eigen_internal_assert(v!=0); 30 #ifdef EIGEN_HAS_OPENMP 31 if(m_maxThreads>0) 32 *v = m_maxThreads; 33 else 34 *v = omp_get_max_threads(); 35 #else 36 *v = 1; 37 #endif 38 } 39 else 40 { 41 eigen_internal_assert(false); 42 } 43 } 44 45 } 46 47 /** Must be call first when calling Eigen from multiple threads */ 48 inline void initParallel() 49 { 50 int nbt; 51 internal::manage_multi_threading(GetAction, &nbt); 52 std::ptrdiff_t l1, l2, l3; 53 internal::manage_caching_sizes(GetAction, &l1, &l2, &l3); 54 } 55 56 /** \returns the max number of threads reserved for Eigen 57 * \sa setNbThreads */ 58 inline int nbThreads() 59 { 60 int ret; 61 internal::manage_multi_threading(GetAction, &ret); 62 return ret; 63 } 64 65 /** Sets the max number of threads reserved for Eigen 66 * \sa nbThreads */ 67 inline void setNbThreads(int v) 68 { 69 internal::manage_multi_threading(SetAction, &v); 70 } 71 72 namespace internal { 73 74 template<typename Index> struct GemmParallelInfo 75 { 76 GemmParallelInfo() : sync(-1), users(0), lhs_start(0), lhs_length(0) {} 77 78 Index volatile sync; 79 int volatile users; 80 81 Index lhs_start; 82 Index lhs_length; 83 }; 84 85 template<bool Condition, typename Functor, typename Index> 86 void parallelize_gemm(const Functor& func, Index rows, Index cols, Index depth, bool transpose) 87 { 88 // TODO when EIGEN_USE_BLAS is defined, 89 // we should still enable OMP for other scalar types 90 #if !(defined (EIGEN_HAS_OPENMP)) || defined (EIGEN_USE_BLAS) 91 // FIXME the transpose variable is only needed to properly split 92 // the matrix product when multithreading is enabled. This is a temporary 93 // fix to support row-major destination matrices. This whole 94 // parallelizer mechanism has to be redisigned anyway. 95 EIGEN_UNUSED_VARIABLE(depth); 96 EIGEN_UNUSED_VARIABLE(transpose); 97 func(0,rows, 0,cols); 98 #else 99 100 // Dynamically check whether we should enable or disable OpenMP. 101 // The conditions are: 102 // - the max number of threads we can create is greater than 1 103 // - we are not already in a parallel code 104 // - the sizes are large enough 105 106 // compute the maximal number of threads from the size of the product: 107 // This first heuristic takes into account that the product kernel is fully optimized when working with nr columns at once. 108 Index size = transpose ? rows : cols; 109 Index pb_max_threads = std::max<Index>(1,size / Functor::Traits::nr); 110 111 // compute the maximal number of threads from the total amount of work: 112 double work = static_cast<double>(rows) * static_cast<double>(cols) * 113 static_cast<double>(depth); 114 double kMinTaskSize = 50000; // FIXME improve this heuristic. 115 pb_max_threads = std::max<Index>(1, std::min<Index>(pb_max_threads, work / kMinTaskSize)); 116 117 // compute the number of threads we are going to use 118 Index threads = std::min<Index>(nbThreads(), pb_max_threads); 119 120 // if multi-threading is explicitely disabled, not useful, or if we already are in a parallel session, 121 // then abort multi-threading 122 // FIXME omp_get_num_threads()>1 only works for openmp, what if the user does not use openmp? 123 if((!Condition) || (threads==1) || (omp_get_num_threads()>1)) 124 return func(0,rows, 0,cols); 125 126 Eigen::initParallel(); 127 func.initParallelSession(threads); 128 129 if(transpose) 130 std::swap(rows,cols); 131 132 ei_declare_aligned_stack_constructed_variable(GemmParallelInfo<Index>,info,threads,0); 133 134 #pragma omp parallel num_threads(threads) 135 { 136 Index i = omp_get_thread_num(); 137 // Note that the actual number of threads might be lower than the number of request ones. 138 Index actual_threads = omp_get_num_threads(); 139 140 Index blockCols = (cols / actual_threads) & ~Index(0x3); 141 Index blockRows = (rows / actual_threads); 142 blockRows = (blockRows/Functor::Traits::mr)*Functor::Traits::mr; 143 144 Index r0 = i*blockRows; 145 Index actualBlockRows = (i+1==actual_threads) ? rows-r0 : blockRows; 146 147 Index c0 = i*blockCols; 148 Index actualBlockCols = (i+1==actual_threads) ? cols-c0 : blockCols; 149 150 info[i].lhs_start = r0; 151 info[i].lhs_length = actualBlockRows; 152 153 if(transpose) func(c0, actualBlockCols, 0, rows, info); 154 else func(0, rows, c0, actualBlockCols, info); 155 } 156 #endif 157 } 158 159 } // end namespace internal 160 161 } // end namespace Eigen 162 163 #endif // EIGEN_PARALLELIZER_H 164
