Merge branch 'v2.4' into v2.5

CHANGES/v2.4.md

@@ -203,6 +203,9 @@ For users:
 
 ## Version 2.4.4 (to be released)
 
+For users:
+  - Fix some performances regression issue with OpenMP
+
 For developers:
   - Small fix in LDFLAGS when enabling coverage.
 

src/tools/OpenMP.cpp

@@ -29,16 +29,37 @@
 
 namespace PLMD {
 
+
+struct OpenMPVars {
+  unsigned cacheline_size=512;
+  bool cache_set=false;
+  unsigned num_threads=1;
+  bool nt_env_set=false;
+};
+
+static OpenMPVars & getOpenMPVars() {
+  static OpenMPVars vars;
+  return vars;
+}
+
+void OpenMP::setNumThreads(const unsigned nt) {
+  getOpenMPVars().num_threads=nt;
+}
+
 unsigned OpenMP::getCachelineSize() {
-  static unsigned cachelineSize=512;
-  if(std::getenv("PLUMED_CACHELINE_SIZE")) Tools::convert(std::getenv("PLUMED_CACHELINE_SIZE"),cachelineSize);
-  return cachelineSize;
+  if(!getOpenMPVars().cache_set) {
+    if(std::getenv("PLUMED_CACHELINE_SIZE")) Tools::convert(std::getenv("PLUMED_CACHELINE_SIZE"),getOpenMPVars().cacheline_size);
+    getOpenMPVars().cache_set = true;
+  }
+  return getOpenMPVars().cacheline_size;
 }
 
 unsigned OpenMP::getNumThreads() {
-  static unsigned numThreads=1;
-  if(std::getenv("PLUMED_NUM_THREADS")) Tools::convert(std::getenv("PLUMED_NUM_THREADS"),numThreads);
-  return numThreads;
+  if(!getOpenMPVars().nt_env_set) {
+    if(std::getenv("PLUMED_NUM_THREADS")) Tools::convert(std::getenv("PLUMED_NUM_THREADS"),getOpenMPVars().num_threads);
+    getOpenMPVars().nt_env_set = true;
+  }
+  return getOpenMPVars().num_threads;
 }
 
 unsigned OpenMP::getThreadNum() {

src/tools/OpenMP.h

@@ -30,6 +30,9 @@ class OpenMP {
 
 public:
 
+/// Set number of threads that can be used by openMP
+  static void setNumThreads(const unsigned nt);
+
 /// Get number of threads that can be used by openMP
   static unsigned getNumThreads();