Re: [ROOT] Using a TMapFile to share a TTree

From: Frankland John (frankland@ganil.fr)
Date: Thu Oct 09 2003 - 14:57:26 MEST


Hi Rene,

thanks for the reply. I modified treeprod and treecons to share a normal 
TFile and
this seems to work OK. However, the "consumer" process gives a few error
messages:
Error in <TFile::ReadKeys>: reading illegal key, exiting after 67 keys
Error in <TFile::ReadKeys>: reading illegal key, exiting after 87 keys
Error in <TFile::ReadKeys>: reading illegal key, exiting after 114 keys
(respectively after 67, 87 and 114 events).
What does this mean (I suppose it probably means that my scripts are not 
correct) ?

John

PS. this is with 3.10/01 binary RH9.0 gcc3.2.2

Rene Brun wrote:

>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
>
>  
>


-- 

John D. Frankland <mailto:frankland@ganil.fr>
Beam Coordinator
GANIL
B.P. 55027
14076 CAEN Cedex 05

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