Re: h2root and Auto append of .dll for a gSystem->Load

From: Rene Brun (Rene.Brun@cern.ch)
Date: Wed Oct 15 1997 - 08:46:05 MEST


Gordon Watts (Brown University) wrote:
> 
> 
> 3) Is it possible to unload a DLL? I have a large ntuple file (many
> columns) converted to a root file. It takes over a minute to open and load
> in the ntuple on my 133 MHz, 40 meg pc and I would like to just leave root
> up and going and then load and unload the DLL I'm testing (I can't run the
> DLL in the interpreter: there is a lot of FORTRAN source code involved...
> bummer.).
> 

Yes, you can unload a dll (see TSystem::Unload). 
Valery will probably comment on the problems with relative paths.
Some changes have been made in this area in the coming version 1.03/05.

Concerning your large ntuple file (well a small one 5 Mbytes), I believe
I understand your problem. Your ntuple has 262 columns.
In the conversion program h2root, I am allocating (by default) 32000
bytes
for the buffer of each branch. This means that you need about 8.4Mbytes
of memory to hold all the buffers + a similar amount to perform
the compression. In the new version, I have changed the default
buffer size from 32K to 8K. This should considerably improve the startup
time when you use the ntuple in a Root session. On my machine it takes
now about 2 seconds to read the necessary buffers in memory.
I should probably be more clever in trying to allocate the buffer size
as a function of the number of columns and ntuple size.

Rene Brun



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