Segmentation Falt: a variable taking random value somehow

ROOT
1

Hi all,

I made a function given below [1]. But at line 62 it takes random value for variable binFill. I am unable to understand why? This patch is very simple and I don’t see anything which can cause this. Please let me know if you find some issue.

I am pasting part of output here [2].

Thanks in advance for your help.

with regards,
Ram

[1]

  33 TH1F* ResetTo4bins(TH1F* wjet, int nbins, double xmin, double xmax){
  34 
  35    TH1F* hOut = new TH1F("hOut",";M_{WW} (Vjet Signal Region);",nbins, xmin, xmax);
  36 
  37    double binWidth = (xmax - xmin)/nbins;
  38 
  39    int binFill = 0;
  40 
  41    double hOutBinContent[4] = {0.0, 0.0, 0.0, 0.0};
  42 
  43    for (unsigned int ibin=1; ibin<wjet->GetNbinsX()+1; ++ibin){
  44      double xlow = wjet->GetBinLowEdge(ibin);
  45      double xhigh = wjet->GetBinLowEdge(ibin+1);
  46 
  47      double xlow_New = hOut->GetBinLowEdge(binFill);
  48      double xhigh_New = hOut->GetBinLowEdge(binFill+1);
  49 
  50      cout<< "binFill = " << binFill << endl;
  51      if (xlow < xlow_New){      cout<<" Don't fill lower bins..." << endl;cout<< "Debug 1: "<< binFill << endl; }
  52      else{
  53         if (xhigh <= xhigh_New)
  54         {
  55            hOutBinContent[binFill] += wjet->GetBinContent(ibin);
  56            cout<< "Debug 2: "<< binFill << endl;
  57         }
  58         else
  59         {
  60            binFill += 1;
  61            hOutBinContent[binFill] += wjet->GetBinContent(ibin);
  62            cout<< "Debug 3: "<< binFill << endl;
  63         }
  64      }
  65 
  66      cout<< "binFill = " << binFill << endl;
  67      cout<<ibin <<  "  xlow = " <<  xlow  <<  " xhigh = " << xhigh <<  "  xlow_New = " <<  xlow_New <<  "  xhigh_New = " <<  xhigh_New <<  "  hOutBinContent[" << binFill << "]      = " << hOutBinContent[binFill] <<endl;
  68 
  69 
  70    }
  71 
  72    return hOut;
  73 
  74 }

[2]

27  xlow = 1900 xhigh = 1950  xlow_New = 1550  xhigh_New = 2025  hOutBinContent[3] = 3.69794
binFill = 3
Debug 2: 3
binFill = 3
28  xlow = 1950 xhigh = 2000  xlow_New = 1550  xhigh_New = 2025  hOutBinContent[3] = 3.86957
binFill = 3
Debug 3: 1069678820
binFill = 1069678820

 *** Break *** bus error
29  xlow = 2000 xhigh = 2050  xlow_New = 1550  xhigh_New = 2025  hOutBinContent[1069678820] =

_ROOT Version: 6.08/05
_Platform: fnal lpc cluster
Compiler: Not Provided

2

Replace line 60 (i.e. binFill += 1;) with:

if (binFill < ((sizeof(hOutBinContent) / sizeof(double)) -1)) binFill++;
else { std::cout << "Ouch!" << std::endl; break; }
3

Dear Coyote,

Thanks for the reply.

Now, I got Ouch!.

28  xlow = 1950 xhigh = 2000  xlow_New = 1550  xhigh_New = 2025  hOutBinContent[3] = 4.15508
binFill = 3
Ouch!

But, even in next loop binFill value should be 3. If you would like to see my full code, please see the attachment. Alpha_calculation.C (60.3 KB)

with regards,
Ram

4

Try with:

TH1F *ResetTo4bins(TH1F *wjet, int nbins, double xmin, double xmax) {
  TH1F *h =
    new TH1F("hOut", ";M_{WW} (Vjet Signal Region);", nbins, xmin, xmax);
  if (wjet) for (Int_t i = 1; i <= wjet->GetNbinsX(); i++)
              h->Fill(wjet->GetBinCenter(i), wjet->GetBinContent(i));
  return h;
}
1 Like
5

Thank you very much Coyote.

It is working now. Earlier I did not realize that this can work.

But, just for information do you have an idea why I was getting the issue in my case?

6

It’s obvious that, when “binFill” is used as the “hOutBinContent” array index, you must make sure that it’s valid for that array.

The TH1::Fill method will automatically make sure that the appropriate bin is incremented (including the “0” underflow bin and the “nbins + 1” overflow bin, if needed).

7

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