On Mon, Sep 8, 2008 at 1:50 PM, Dr A. Zaman
<[log in to unmask]> wrote:
Hi Darren,
Many thanks for the quick response.
I am at the model estimating stage using spm2,
even with 15 subjects (-albeit 444vols/subject),
Well, Windows does not win the prize for memory management.
I get the notorious memory error. Would a 64bit/8GB work for sure?
Possibly. I didn't ask how big your images are, but no matter. If you have access to a Linux machine you might try the analysis there. That would give you a better idea on the likelihood of working.
You can check the maxmem setting in spm_defaults. If it is more than 2^20 it is possible that lowering the value would load less data at a time and that might help. Using less than 2^20 is usually not helpful and will increase the run time enormously. (I've never found this makes much of a difference, but you can try it. Memory errors usually occur in relation to manipulating the large covariance matrices.) You can try turning off java in matlab - I think matlab -nojvm when you start matlab from a shortcut. You can check what other processes you have running and close all non-essential programs.
Also, if I
re-run the model estimation is SPM5, is it going
to be any easier (assuming I pre-process my data in SPM5)?
No. Won't make a difference regarding memory issues.
Darren
best wishes,
Arshad
On Mon, 8 Sep 2008, Darren Gitelman wrote:
Hi Arshad
I don't think you will be able to do this with less than a 64 bit machine
and 8 gb ram if you want to analyze them all together (i.e., a big fixed
effects analysis). However, with 30 subjects I would think you would have
sufficient numbers to perform a random effects analysis, in which case each
subject could be analyzed separately and that should certainly work.
regards,
darren
On Mon, Sep 8, 2008 at 11:43 AM, Dr A. Zaman <[log in to unmask]> wrote:
Dear SPM experts,
I was wondering if anyone can suggest approx. how much
RAM is needed in order to model fMRI data consisting
of 30 subjects, 8 conditions, 444 (3mm/isotropic) volumes?
I have used a pc with 4GB RAM with no joy, could not even run
half the number of subjects. Prior to getting hold of an 8GB
machine, can I cam sure that it will work? Any comments will be greatly
appreciated.
Many thanks,
Arshad
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Dr. A Zaman,
Clinical Sciences Centre,
University Hospital Aintree,
Lower Lane,
Liverpool, UK.
L9 7AL.
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Darren Gitelman
