Hi, Fons Rademakers wrote: > Coming back to Damir's original remark on histogram drawing performance. > It was related to very large histograms (several thousands of bins). Indeed > the refresh of such histograms is relatively time consuming since the > histogram paint method clears the entire pad/canvas and redraws > the complete histogram, not just the changed bins, axis and stats. > However, even if a "fast" histogram redrawing would be implemented one > wants to use the double buffered method to avoid screen flicker and to > support efficient window refreshing. A "fast" histogram drawing method > would require something like a shadow bin array (or bin bitmap) needed > to know which bins have to be erased and redrawn. Extra complications > are that bin erasing can cause mutilation of grid lines, functions and > any other objects drawn in the pad. A "fast" histogram repaint method > would probably require that no other objects will be allowed in the pad. After some experimentation, it appears that I'm able to plot quite fast the time series I need. In fact, it took me a while to understand that there is an efficient plotting of large histograms but only for the line drawing option "L". And a small bug in the TGraph.cxx source as well ! Reducing the size of the pad a bit, removing stat box and using the strict minimum axis labels, I was able to get a speed which is roughly 1.5-2 slower than Paw in the same context. Not so bad ! Thanks to all of you, especially Fons and Eddy. Damir -- ===================================================================== | Damir Buskulic | Universite de Savoie/LAPP | | | Chemin de Bellevue, B.P. 110 | | Tel : +33 (0)450091600 | F-74941 Annecy-le-Vieux Cedex | | e-mail: buskulic@lapp.in2p3.fr | FRANCE | ===================================================================== mailto:buskulic@lapp.in2p3.fr
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