[Gate-users] problem with gjm

[Peter Herrick]

Hi all,

 

Sadly I meant with respect to a block of crystals in my detector – the
#counts in the blockID  histogram (in root) seem to fluctuate by much
greater than the anticipated amount à (#counts) ^ 0.5. Changing from the
MersenneTwister Engine seemed to fix this problem  - examining an individual
rootfile before merging them all seemed to indicate a fluctuation much
closer to the anticipated amount, but the gjm gave the error.

Any other ideas?

 

Thanks,

Peter.

 

From: Simon Stute [mailto:gate.stute at gmail.com] 
Sent: 04 March 2010 15:29
To: Peter Herrick
Cc: gate-users at lists.opengatecollaboration.org
Subject: Re: [Gate-users] problem with gjm

 

Hi Peter,

When you talk about fluctuations in the number of singles for each "block",
do you mean split macros (in the meaning of a job) or do you physically mean
a block in your detector ?
In the first case, did you use the following command in your main macro

/gate/cluster/setTimeSplitHalflife

Because if you did not use it, each split is equally divided along the
simulation time, so depending on the half-life of your isotope each split
will contain a different number of singles.

Hope this helps !
Simon

On Thu, Mar 4, 2010 at 3:40 PM, Peter Herrick <pdeh2 at cam.ac.uk> wrote:

Dear GATE users,

I have been using version 4.0  with linux in a cluster arrangement to
simulate a PET scanner. I have found that the fluctuations in the number of
singles events for each block are MUCH greater than those expected from
poisson statistics - After looking at the seeds created when I employ gjs,
the same numbers are appearing in each 'seed.rndm' file in different orders.
To solve I have tried switching back to the HepJamesRandom engine, but as a
result the Job merger is no longer working - I wondered if anyone has any
ideas?

The change that I implemented was the one Simon suggests in the thread 'same
running on Gate' which can be found below.

http://lists.opengatecollaboration.org/mailman/private/gate-users/2009-April
/subject.html

but there is no mention of gjm not working. The error I recieve is:


 *** Break *** segmentation violation
(no debugging symbols found)
Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1".
Attaching to program: /proc/17367/exe, process 17367
done.
Failed to read a valid object file image from memory.
0xb7f95410 in ?? ()

which I have never seen before. Any help or suggestions would be much
appreciated.

Thanks,

Peter Herrick,
Wolfson Brain Imaging Centre
University of Cambridge

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