Histogram limitation?

ROOT
1

Dear All,

I got rid of my previous problem of PAR archive and custom library.
At this moment, I am really running PROOF to understand the idea of running parallel workers.
So this question is more theoretical.

I have a tree with 5 quantities:

  • a “run” number ( a running number currently I am between 250000 and 260000)
  • a “spill” number (from 1 to 200)
  • a “counter” (from 1 to … the infinite or whatever, it’s usually millions)
  • a “timeinspill” value (from 1 to 15 secondes)

I would like to plot run:spill for example. Nevertheless, I noticed that TSelector::Init() is called each time a new TTree is cached.

Basically you have :

Begin()
     BeginSlave()
           Init()
           Process()
           Init()
           Init()
      EndSlave()
      [.. repeat ..]
Terminate()
  • I create my histogram when I use BeginSlave();
  • Usually I set my tree pointer at the Init() function.

Here is the problem… If I want to draw “timeinspill:spill” that’s work because it’s a well known range.
But when I want to display “timeinspill:counter” or “run:spill”, I don’t know how to initialize my histogram !! Since I don’t know the upper limit of my histogram.

I am working with ROOT 5.34.36, I tried many things… But is there a easy solution to correctly draw this ?
I already tried to Input a value before using TChain::Process(), but that doesn’t make sense… because I have to read all my tree…

Any comment is very welcome :slight_smile:
Thank you

2

Dear meyerma,

If I have understood correctly your post, your problem may be solved by using automatic binning, whihc you enable by specify the number of bins and setting the lower bound greater or equal the upper one (see root.cern.ch/doc/master/classTH1.html). The boundaries are calculated automatically and communicated among workers.

G Ganis

3

Dear Ganis,

Thanks for the quick answer ! :slight_smile: Actually I read that point of the documentation. Then the problem would be to define correctly the number of bin… That’s just translate the problem I guess…

Edit: It would have been more convinient to be able to force the bin width. because if I don’t know the range, it can be quite complicate to set correctly the binning!