Dear Rooters,
after we have started using the multi-threaded version of ROOT for the online
monitoring in the PHENIX experiment, I came across a little problem drawing a
2-dim histogram with "LEGO2". It draws fine the first time you plot it. Then the
background threads keeps filling the histogram. When you redraw the updated
histogram, the updated bins stick out as black spikes, apparently because the
mapping of colors to the (now changed) min-max range isn't updated. I put two
pictures at
http://mlp.rhic.bnl.gov/lego2-root/index.html
to show the effect. It looks like the histogram doesn't realize that its
contents have been modified after the last draw. The same goes for
one-dimensional histos when plotted with "LEGO2".
This has nothing to do with the fact that we use multi-threading, by the way,
except that we redraw updated histos frequently in our online monitoring
application and the problem showed up here. If you just fill a histogram, draw
it with lego2, fill some more, redraw it, you will see it.
Thanks,
Martin
--
Martin L. Purschke ; purschke@bnl.gov
; http://www.phenix.bnl.gov/~purschke
;
Brookhaven National Laboratory ; phone: +1-516-344-5244
Physics Department Bldg 510 C ; fax: +1-516-344-3253
Upton, NY 11973-5000 ;
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