1 /* +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 2 Copyright (c) 2014-2021 The plumed team 3 (see the PEOPLE file at the root of the distribution for a list of names) 4 5 See http://www.plumed.org for more information. 6 7 This file is part of plumed, version 2. 8 9 plumed is free software: you can redistribute it and/or modify 10 it under the terms of the GNU Lesser General Public License as published by 11 the Free Software Foundation, either version 3 of the License, or 12 (at your option) any later version. 13 14 plumed is distributed in the hope that it will be useful, 15 but WITHOUT ANY WARRANTY; without even the implied warranty of 16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 17 GNU Lesser General Public License for more details. 18 19 You should have received a copy of the GNU Lesser General Public License 20 along with plumed. If not, see <http://www.gnu.org/licenses/>. 21 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ */ 22 #ifndef __PLUMED_tools_OpenMP_h 23 #define __PLUMED_tools_OpenMP_h 24 25 #include <vector> 26 27 namespace PLMD { 28 29 class OpenMP { 30 31 public: 32 33 /// Set number of threads that can be used by openMP 34 static void setNumThreads(const unsigned nt); 35 36 /// Get number of threads that can be used by openMP 37 static unsigned getNumThreads(); 38 39 /// Returns a unique thread identification number within the current team 40 static unsigned getThreadNum(); 41 42 /// get cacheline size 43 static unsigned getCachelineSize(); 44 45 /// Get a reasonable number of threads so as to access to an array of size s located at x 46 template<typename T> 47 static unsigned getGoodNumThreads(const T*x,unsigned s); 48 49 /// Get a reasonable number of threads so as to access to vector v; 50 template<typename T> 51 static unsigned getGoodNumThreads(const std::vector<T> & v); 52 53 }; 54 55 template<typename T> getGoodNumThreads(const T * x,unsigned n)56unsigned OpenMP::getGoodNumThreads(const T*x,unsigned n) { 57 unsigned long p=(unsigned long) x; 58 (void) p; // this is not to have warnings. notice that the pointer location is not used actually. 59 // a factor two is necessary since there is no guarantee that x is aligned 60 // to cache line boundary 61 unsigned m=n*sizeof(T)/(2*getCachelineSize()); 62 unsigned numThreads=getNumThreads(); 63 if(m>=numThreads) m=numThreads; 64 else m=1; 65 return m; 66 } 67 68 69 template<typename T> getGoodNumThreads(const std::vector<T> & v)70unsigned OpenMP::getGoodNumThreads(const std::vector<T> & v) { 71 if(v.size()==0) return 1; 72 else return getGoodNumThreads(&v[0],v.size()); 73 } 74 75 76 } 77 78 #endif 79