By the way,
It sounds you call your
p2DH->Draw("colz");
gPad->GetCanvas()->Update();
in loop. It is not necessary to call the method Draw in loop. It is
sufficient to call Draw at once, and then call Update only.
Cheers, Valeri
-----Original Message-----
From: owner-roottalk@pcroot.cern.ch
[mailto:owner-roottalk@pcroot.cern.ch] On Behalf Of Ed Oltman
Sent: Friday, August 30, 2002 5:35 PM
To: Roottalk@Pcroot. Cern. Ch
Subject: [ROOT] Performance question: Updating a colz histogram
Hello,
I have an online application which includes a 500x500 bin TH2F which I
display in response to a timer with
p2DH->Draw("colz");
gPad->GetCanvas()->Update();
(I've previously called gStyle->SetPalette(1,0)) Early on, when the
histogram is still young, the refresh is pretty quick - refreshing at 2
Hz
uses a small amount (<10%) of the cpu time. Gradually, as the histogram
fills, the refresh time increases - by the time the histogram has a few
hundred thousand entries, (maximum bin contents is in the 10s) the cpu
time
is 80% and climing.
Is there something I could do to speed things up, short of adjusting the
refresh rate? I am using version 3.03/08 on Win32. Thanks...
Ed Oltman
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