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Question Event size in storage with extended/persistency example 

Forum: Documentation and Examples
Date: 10 May, 2006
From: Emanuele Leonardi <Emanuele Leonardi>

I am using the G4PersEx01 example from examples/extended/persistency to add ROOT persistency to my simulation.

While running the example using G4 version 7.1.p01 I noticed that the file size does not grow linearly with the number of events written.

This is the file and event size I get when I run the example with different number of events:

     1 evt    6 KB -> 6.0 KB/evt
   100 evt  552 KB -> 5.5 KB/evt
  1000 evt  4.8 MB -> 4.8 KB/evt
  5000 evt   30 MB -> 6.0 KB/evt
 10000 evt   65 MB -> 6.5 KB/evt
 50000 evt  455 MB -> 9.1 KB/evt

In addition, as each hit consists of 4 float quantities, and as each event has 2 to 8 hits (I am using the default .mac file with 30 MeV positrons), I would expect an average events size of ~80 bytes (5x4x4), so I cannot understand where this 6KB+ per event comes from.

It is clear that I am missing some basic information here. Can anybody explain what I am seeing?

Thank you very much

                Emanuele Leonardi

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