[Numpy-discussion] advanced indexing bug with huge arrays?

David Warde-Farley wardefar@iro.umontreal...
Mon Jan 23 12:55:52 CST 2012


I've reproduced this (rather serious) bug myself and confirmed that it exists
in master, and as far back as 1.4.1.

I'd really appreciate if someone could reproduce and confirm on another
machine, as so far all my testing has been on our single high-memory machine.

Thanks,
David

On Mon, Jan 23, 2012 at 05:23:28AM -0500, David Warde-Farley wrote:
> A colleague has run into this weird behaviour with NumPy 1.6.1, EPD 7.1-2, on Linux (Fedora Core 14) 64-bit:
> 
> > a = numpy.array(numpy.random.randint(256,size=(5000000,972)),dtype='uint8')
> > b = numpy.random.randint(5000000,size=(4993210,))
> > c = a[b]
> 
> It seems c is not getting filled in full, namely:
> 
> > In [14]: c[1000000:].sum()
> > Out[14]: 0
> 
> I haven't been able to reproduce this quite yet, I'll try to find a machine with sufficient memory tomorrow. But does anyone have any insight in the mean time? It smells like some kind of integer overflow bug.
> 
> Thanks,
> 
> David
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