Bug in TH1F when working with lots of events

Dear ROOT experts,

I have been working with ntuples with lots of events (>10^8) evts and doing a skimming over them. During the skimming I fill a cutflow histogram indicating how many events pass certain selections.

The problem is that when working with so many events, the cutflow histogram stops working after 16777216 events, meaning that the bins are not filled past that value.

I leave attached a minimal working example, in which I loop over 100000000 (1x10^7) events and check if the number is divisible by an integer. The result I got is the same one I got when working with the ntuple:

Processing test.cxx...
                    All events =  16777216
                Divisible by 2 =  16777216
          Divisible by 3 and 2 =  16666667
       Divisible by 4, 3 and 2 =  8333334

I repeated the test with less events 10000000 (10^6) and worked fine:

Processing test.cxx...
                    All events =  10000000
                Divisible by 2 =  5000000
          Divisible by 3 and 2 =  1666667
       Divisible by 4, 3 and 2 =  833334

It would be very much appreciated if you could tell me how to solve this issue.

Thanks in advance,


test.cxx (1.5 KB)
test.root (3.8 KB)

ROOT Version: 6.24/06
Platform: MacOS and lxplus

1 Like

Thank you very much!!.. and sorry for asking this naive question…

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