Re: [ROOT] drawing speed problem with release 3/05 of ROOT ?

From: Rene Brun (Rene.Brun@cern.ch)
Date: Sat Jul 12 2003 - 15:01:57 MEST


Hi Damir,

I have modified the clipping algorithm to be more efficient in case
of histograms with many bins as in your case.
Please try the CVS head version and let me know the result.
I would be very interested in getting a small script for the case
where you claim to lose a factor 4.

Rene Brun

Damir Buskulic wrote:
> 
> Hi,
> 
> There seems to be a drawing speed problem in the version 3/05.04 that
> we use for online display. The small macro attached gives the following
> results :
> 
> Under OSF1/v5 (alpha XP1000 667 MHz):
> root/v3/05.04:  Real Time = 12.25 seconds  Cpu Time = 6.40 seconds
> root/v3/03.08:  Real Time =  8.47 seconds  Cpu Time = 3.52 seconds
> 
> Under Linux/RedHat v7.1 (PC i686 1.8 GHz):
> root/v3/05.04:  Real Time = 14.40 seconds  Cpu Time = 5.06 seconds
> root/v3/03.08:  Real Time = 10.13 seconds  Cpu Time = 3.36 seconds
> 
> Does anyone see this ? Were there changes in the low level layers of
> ROOT or in TH painter that could explain this ? On some of our programs
> we saw a speed decrease of a factor 4 but this is much more difficult
> to characterize simply. So here is the program :
> 
> ______________________________________________________________
> #include "TPad.h"
> #include "TBenchmark.h"
> #include "TH1.h"
> 
> void test_speed()
> {
>    gBenchmark->Reset();
>    gBenchmark->Start("testspeed");
>    TH1F* h = new TH1F("h","test_speed",20000,0,1);
>    h->FillRandom("pol1",10000);
>    for (int i=0;i<100;i++) {
>       h->Draw();
>       gPad->Update();
>    }
>    gBenchmark->Show("testspeed");
> }
> ______________________________________________________________
> 
> By the way, the difference is seen in interpreted as well as compiled
> mode.
> 
> We would be grateful if anybody can help
> 
> Cheers
> 
> Damir
> 
> ====================================
> Damir Buskulic,  Universite de Savoie/LAPP
> Chemin de Bellevue, B.P. 110, F-74941 Annecy-le-Vieux Cedex, FRANCE
> Tel : +33 (0)450091600
> e-mail: buskulic@lapp.in2p3.fr
> ====================================



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