Delete TH1 and TFile: memory consumption increases

[lizardo.valencia]

Dear experts

The following function inside an event loop is making the memory consumption to increase:

Double_t S0percentile(Int_t nCharged, Double_t S0)
{

  TFile *InputFile = new TFile("S0classes.root", "read");
  TH1D *h = (TH1D *)InputFile->Get(Form("hProjYMult%dnew",nCharged));
  Int_t S0bin = h->GetXaxis()->FindBin(S0);
  Double_t S0percent = h->GetBinContent(S0bin);
  delete h;
  InputFile->Close();
  delete InputFile;
  
  return S0percent;
  
}

Where S0classes.root is a root file that contains many TH1 objects. The idea is that this root file has to be read for each event, choose a particular TH1 and extract some information. I think Im correctly deleting the histogram and the file, but I dont know why this function creates a memory leak.

Thanks for your help!

Im using Root v6-14-02, Pythia v8.235 and Ubuntu 18.04.3 LTS

[pcanal]

There are no obvious leak in that code. Did you verify that it is ‘that’ routine that is introducing the leak? (how did you do this verification?)

[lizardo.valencia]

If I coment out the function everything works perfect. Indeed, the dummy function

Double_t S0percentile(Int_t nCharged, Double_t S0)
{

TFile* InputFile = nullptr;
TH1D* h = nullptr;

Double_t S0percent = 0.0;
delete h;
delete InputFile;

return S0percent;

}

Works OK, indicating that Tfile and the TH1 are being deleted correctly. Furthermore if I include, in the previous dummy function, the line

InputFile = TFile::Open(“S0classes.root”);

Then the memory consumption starts to increase, but I dont understand why. This line indicates that the root file is being opened and deleted for each event.

Regards,
Lizardo

PS. I dont know if it is related, but Im using this routine within a Pythia simulation.

[pcanal]

PS. I dont know if it is related, but Im using this routine within a Pythia simulation.

Can you try that function outside of the Pythia simulation?

[lizardo.valencia]

Exactly the same happens in CRMC that reads a simulation output from a .hepmc file
Should I test this function in an only-Root code? If so, can you point me to a example (inside $ROOTSYS?) where I can do it?

Regards,

[pcanal]

you could create a file runmany.C containing just:

Double_t S0percentile(Int_t nCharged, Double_t S0)
{

  TFile *InputFile = new TFile("S0classes.root", "read");
  TH1D *h = (TH1D *)InputFile->Get(Form("hProjYMult%dnew",nCharged));
  Int_t S0bin = h->GetXaxis()->FindBin(S0);
  Double_t S0percent = h->GetBinContent(S0bin);
  delete h;
  InputFile->Close();
  delete InputFile;
  
  return S0percent;
  
}
void runmany(size_t howmany = 100) {
   for(size_t i = 0; i < howmany; ++i) {
      S0percentile(1,1);
  } 
}

and do

root.exe -b -l -q 'runmanyC(10000000)'

and see if the memory grows …

[Wile_E_Coyote]

Try:

Double_t S0percentile(Int_t nCharged, Double_t S0) {
  Double_t v = 0.;
  TFile *f = TFile::Open("S0classes.root");
  if (!f || f->IsZombie()) { delete f; return v; } // just a precaution
  TH1D *h; f->GetObject(TString::Format("hProjYMult%dnew", nCharged), h);
  if (!h) { delete f; return v; } // just a precaution
  Int_t b = h->FindFixBin(S0); // may return under-/over-flow bins
  if (b >= 1 && b <= h->GetNbinsX()) v = h->GetBinContent(b);
  delete f; // automatically deletes "h", too
  return v;
}