Line data    Source code

       1             : /* +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
       2             :    Copyright (c) 2014-2023 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>
      56       87124 : unsigned OpenMP::getGoodNumThreads(const T*x,unsigned n) {
      57             :   unsigned long long p=(unsigned long 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       87124 :   unsigned m=n*sizeof(T)/(2*getCachelineSize());
      62       87124 :   unsigned numThreads=getNumThreads();
      63       87124 :   if(m>=numThreads) m=numThreads;
      64             :   else m=1;
      65       87124 :   return m;
      66             : }
      67             : 
      68             : 
      69             : template<typename T>
      70         450 : unsigned OpenMP::getGoodNumThreads(const std::vector<T> & v) {
      71         450 :   if(v.size()==0) return 1;
      72         438 :   else return getGoodNumThreads(&v[0],v.size());
      73             : }
      74             : 
      75             : 
      76             : }
      77             : 
      78             : #endif