[Mne_analysis] Size limit of data?

[Martin Luessi]

Hi Arnaud,

I think this is expected due to the limited memory of your computer.
After applying tfr, your data needs about 6.5GB of memory (3 *2 * 70 *
1000 * 129 * 128 bits) and before tfr half of that (3.2GB), so you are
exceeding the 8GB available on your computer. Some things that you could
do to save memory:

- Downsample the data to e.g. 500Hz. This would cut the memory needed by
half.

- Process one trial at a time, save the data to file and load it later
for analysis (like that you won't have the 3.2GB original data in memory).

HTH,

Martin

On 05/12/14 06:06, Arnaud Ferre wrote:
> Hi everyone,
> 
> I do some analysis in time-frequency, notably, I calculate PSD. I use
> functions of mne.time_frequency.tfr.
> I think that the common time of your trials is some seconds. But I think
> that there is a common limit to the data size.
> Maybe have I exceeded it?
> 
> My trials last 70sec and contain 700 000 values.
> When I test only 3 trials (epochs) on 2 channels (so only 6 data
> packages) with the function induced_power(), my computer struggles (so
> with a full test, my computer dies)!
> I don't use a raw object (because my ECG data are not compatible), but I
> don't think that it would be a problem for the time being.  
> I use Fs = 1000 and frequencies=np.arange(1, 130, 1). My computer has a
> 4 cores of 3.20GHz and 8.00Go of RAM, 64bits.
> 
> Is this normal due to the size of my data/my computer power?
> If yes, how can I improve it (change computer, cut my trials, force to
> free memory...)?
> If no, an idea of my possible problem?
> 
> Thank by advance,
> Best,
> Arnaud
> 
> 
> 
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-- 
Martin Luessi, Ph.D.

Research Fellow

Department of Radiology
Athinoula A. Martinos Center for Biomedical Imaging
Massachusetts General Hospital
Harvard Medical School
149 13th Street
Charlestown, MA 02129

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