Hello Eddy, I am not sure you correct. It is true "TGraph::PaintGrapHist" does take in account the screen resolution but ExecuteEvent. see: http://root.cern.ch/root/htmldoc/src/TGraph.cxx.html#TGraph:ExecuteEvent When one tries to move the graph (may be accidently, just the wrong mouse button was pressed) this entails the graph of the all fNpoints to be redrawn at least twice: The first time to clear the old graph position and the second time to draw it at the new place. Each of 10^7 points is drawn with 6 calls to TVirtualX::DrawLine sending at list 4 coordinate numbers as an X11-message. This means just one touched (occasionally) the middle button of the mouse the (4*2) * 2 * 6 * 10^7 bytes will be sent out to X-terminal. I believe this may shock the networking. Assuming we have 10Mbit / sec network one can calculate that 10^10 / 10 ^7 = 1000 sec per single mouse step (this assumes the X-terminal response time is as fast as its networking connection) -----Original Message----- From: Eddy Offermann To: Tony.Colley@itt.com Cc: roottalk@pcroot.cern.ch Sent: 2/26/02 12:46 PM Subject: Re: [ROOT] Event handling or graphing huge datasets Hi Tony, Take a look at "void TGraph::PaintGrapHist" and scan for "lowRes". You will see around line 2350 that if you draw the graph with option L or P, The number of data points is checked versus your screen resolution. In case of many data points it will not draw every point but just calculate the average pixel position. 10^7 should not be a problem Eddy A.J.M. Offermann Renaissance Technologies Corp. Route 25A, East Setauket NY 11733 e-mail: eddy@rentec.com http://www.rentec.com
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