[ROOT] Multiple booking

From: Robert Zitoun (zitoun@fnal.gov)
Date: Wed Nov 28 2001 - 23:25:10 MET


  Hi Rooters

 I am trying to book 50,000 histograms in a macro doing

TH1F *h[50000];
char text[100];

  for( int chan=0 ; chan<50000 ; chan++ )
  {
    sprintf(text, "h%d", chan);
    h[chan] = new TH1F( text, "", 15, 0, 15);
  }

It take me 20 minutes to get histos booked. The booking time for one
histogram increased with its ordinal number (quite fast in the beginnig,
verrry slow for the last ones). I even used a compiled version to get it
done in 20'.

 There is certainly a more clever (faster) way to do it. Can you tell me ?
Also can you tell why what it did is so long.

                  Thank you

                                 Robert Zitoun, Stony Brook and Annecy



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