Created attachment 333 [details]
source code & docs

The Modification of G4Allocators allowing the

fast garbage collection ( no reallocation of existing dat & preserving prellocated heap  below some threshold)

in 3 different modes:


1.   fully  automatic

2.   by demand  (e.g. in end of event)

3.   by demand mode allowing to clean up some G4Allocators by name assuming being empty eg at the end of event  /intrinsically unsafe/ 
 

To setup garbage collection the following function should be called at the beginning of user job 

G4Allocator::SetGarbageCollection(long long threshold_in_bytes,bool autogarbage);///< default values threshold_in_bytes=4000000 autogarbage=false

for mode 2. additional call is needed (eg in user end of event or directly in ./source/run/src/G4WorkerRunManager.cc
     G4AllocatorList *fa=G4AllocatorList::GetAllocatorListIfExist();
     if(fa)fa->CollectGarbage();
 
mode 3. requires G4Allocator::SetGarbageCollection(0) call at the beginning of user job

next at   end of event the " grbage collection"  can be invoked as shown below.  Note that this method can not be applied to original G4Allocators as they don;t contain an object name and  some objects (G4NavigationLevelRep, ..TouchableHistory..) persists between different events.   

// Unsafe Nethod if  no garbage collection done
 G4AllocatorList *fa=G4AllocatorList::GetAllocatorListIfExist();
double G4AllocatorSize=some_threshold;
if(!G4AllocatorPool::GarbageCollectionOn()){
for(int k=0;k<fa->fList.size();k++){
  if(fa->fList[k]->GetAllocatedSize()>G4AllocatorSize &&strstr(fa->fList[k]->tn.c_str(),"G4Track")){
     fa->fList[k]->ResetStorage();
  }
  if(fa->fList[k]->GetAllocatedSize()>G4AllocatorSize &&strstr(fa->fList[k]->tn.c_str(),"G4DynamicParticle")){
     fa->fList[k]->ResetStorage();
  }
}
}
 
Modes 1. and 2. are fully implemented in the attached tar file.


Performance example base on electrons momentum (P) 1/P distribution [2,10000] GeV/c :

Dynamic allocation drawing g4a.eps

Mode         CPU overhead per event (%)       Average G4AllocatorSize per thread for last half of events, MBytes

Original             0                               500

Mode 3               0                               320        

Mode 2               4.5                             287

Mode 1               7.5                             285