Problem 2200

Summary:	G4VParticleChange::SetNumberOfSecondaries() Warning theListOfSecondaries is not empty
Product:	Geant4	Reporter:	Javier Muñoz <javier.munoz.vidal>
Component:	processes/optical	Assignee:	Daren Sawkey <daren.sawkey>
Status:	RESOLVED FIXED
Severity:	minor
Priority:	P4
Version:	10.5
Hardware:	Apple
OS:	Mac OS X

Description Javier Muñoz 2019-10-24 19:41:53 CEST

I'm running a simulation with just opticalPhotons. It always finishes OK, although many times I get the following warning (or warnings as it may appear more than once) when the simulation has finished:

G4VParticleChange::SetNumberOfSecondaries() Warning  theListOfSecondaries is not empty

I only get these warnings if I set a value for the property "WLSMEANNUMBERPHOTONS" in the G4MaterialPropertiesTable of one of the materials I use.
The larger the number I set for this property, the more times I get the Warning.
If I do not specify any specific value for this property, I get NO warnings.

Comment 1 Daren Sawkey 2019-10-28 16:43:12 CET

Thanks for reporting this. It is now fixed for the upcoming release.

Comment 2 Javier Muñoz 2019-10-28 18:40:51 CET

Does it have a significant impact on the results got with current version ??

Comment 3 Daren Sawkey 2019-10-29 02:06:16 CET

It can change the results, when the absorbed photon has an energy close to the low energy limit of the emission spectrum. (This might not be realistic.) For each emitted photon, the code will try to sample the energy from the spectrum, such that the emitted photon energy is less than the absorbed photon energy. If this can't be done, the number of secondaries is reduced by 1. This unintentionally deleted any photons that were previously generated this step.

The diff is below (changes to printouts suppressed). If you like, you can try it and report back.



diff --git a/source/processes/optical/src/G4OpWLS.cc b/source/processes/optical/src/G4OpWLS.cc
index 62469cdd82..639adfcc68 100644
--- a/source/processes/optical/src/G4OpWLS.cc
+++ b/source/processes/optical/src/G4OpWLS.cc
@@ -100,12 +100,13 @@ G4OpWLS::~G4OpWLS()
 G4VParticleChange*
 G4OpWLS::PostStepDoIt(const G4Track& aTrack, const G4Step& aStep)
 {
+  std::vector<G4Track*> proposedSecondaries;
   aParticleChange.Initialize(aTrack);
   
   aParticleChange.ProposeTrackStatus(fStopAndKill);

@@ -144,8 +145,6 @@ G4OpWLS::PostStepDoIt(const G4Track& aTrack, const G4Step& aStep)
 
   }
 
-  aParticleChange.SetNumberOfSecondaries(NumPhotons);
-
   G4double primaryEnergy = aTrack.GetDynamicParticle()->GetKineticEnergy();
 
   G4int materialIndex = aMaterial->GetIndex();

@@ -191,19 +190,26 @@ G4OpWLS::PostStepDoIt(const G4Track& aTrack, const G4Step& aStep)
     // If no such energy can be sampled, return one less secondary, or none
 
     if (sampledEnergy > primaryEnergy) {

        NumberOfPhotons--;
-       aParticleChange.SetNumberOfSecondaries(NumberOfPhotons);
        if (NumberOfPhotons == 0) {

           // return unchanged particle and no secondaries
+          aParticleChange.SetNumberOfSecondaries(0);
           return G4VDiscreteProcess::PostStepDoIt(aTrack, aStep);
        }
        continue;
     
@@ -268,10 +274,14 @@ G4OpWLS::PostStepDoIt(const G4Track& aTrack, const G4Step& aStep)
     // aSecondaryTrack->SetTouchableHandle((G4VTouchable*)0);
     
     aSecondaryTrack->SetParentID(aTrack.GetTrackID());
-    
-    aParticleChange.AddSecondary(aSecondaryTrack);
+
+    proposedSecondaries.push_back(aSecondaryTrack);
   }
 
+  aParticleChange.SetNumberOfSecondaries(proposedSecondaries.size());
+  for (auto sec : proposedSecondaries) {
+    aParticleChange.AddSecondary(sec);
+  }
   if (verboseLevel>0) {
     G4cout << "\n Exiting from G4OpWLS::DoIt -- NumberOfSecondaries = " 
           << aParticleChange.GetNumberOfSecondaries() << G4endl;