[Numpy-discussion] Apparently non-deterministic behaviour of complex array multiplication

[kneil]

Hi Pierre, 
I was thinking about uploading some examples but strangely, when I store the
array using for example: np.save('Y',Y)
and then reload it in a new workspace, I find that the problem does not
reproduce.  It would seem somehow to be
associated with the 'overhead' of the workspace I am in...

The context here is that I read in 24 files, totaling about 7GB, and then
forming data matrices of size 24 x N, where N varies.  I tried for example
this morning to run the same code, but working with only 12 of the files -
just to see if NaNs appeared.  No NaN appeared however when the machine was
being less 'taxed'.

Strangely enough, I also seterr(all='raise') in the workspace before
executing this (in the case where I read all 24 files and do net NaN) and I
do not get any messages about the NaN while the calculation is taking place.  
 
If you want to play with this I would be willing to put the data on a file
sharing site (its around 7.1G of data) together with the code and you could
play with it from there.  The code is not too many lines - under 100 lines,
and I am sure I could trim it down from there.

Let me know if you are interested.
cheers, 
K


Pierre Haessig-2 wrote:
> 
> Le 01/12/2011 02:44, Karl Kappler a écrit :
>> Also note that I have had a similar problem with much smaller arrays, 
>> say 24 x 3076
> Hi Karl,
> Could you post a self-contained code with such a "small" array (or even 
> smaller. the smaller, the better...) so that we can run it and play with 
> it ?
> -- 
> Pierre
> 
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