John, A Tree in a TMapFile works, but this is not a solution for large trees. You cannot make your Tree bigger than the shared memory segment. It is better to use a normal tree overflowing on disk. The Tree_Writer and the Tree_Reader being in separate processes/machines. To make sure that the reader has a coherent/safe view of the writer process see comments in TDirectory::SaveSelf Rene Brun > Frankland John wrote: > > Hi Rene, > > Well, that was a stupid mistake, proving that after a certain hour it is > better to go to bed > than to keep "working"! Thanks a lot. However, as regards my other questions, > have you > any advice ? Because in the various messages I read in the ROOTtalk digest, it > seemed > that a TTree could not exist in a TMapFile, or wouldn't work correctly, but I > don't know if > these messages were only pertinent to the older versions of ROOT ? > > Best regards > John > > Also, is it possible to share the TTree in this way and still write it to disk > ? > Because when I tried to open the TMapFile after stopping the scripts I was > informed > (quite logically) that said file is not a TFile... Is it just a buffer of > sorts ? > > What I actually want to be able to do is to store incoming data acquisition > events in a TTree > whilst an independent process triggered by a certain type of event would then > look back through > all the previously stored events for some correlation. Is this the best (only) > way to do it ? > > Rene Brun wrote: > > > Hi John, > > > > You have an error in treecons.C. > > When a Tree has N entries, the last entry number is N-1. > > Your program will work if you change treecons.C as shown below. > > > > Rene Brun > > > > > > > > -- > > John D. Franklandtel: +33 > Beam Coordinator (0)231454628 > GANIL fax: +33 > B.P. 55027 (0)231454665 > 14076 CAEN Cedex > 05
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