[Numpy-discussion] bug in numarray.maximum.reduce ?

Sebastian Haase haase at msg.ucsf.edu
Fri Jul 2 10:46:01 CDT 2004


On Friday 02 July 2004 09:02 am, Todd Miller wrote:
> On Fri, 2004-07-02 at 11:27, Sebastian Haase wrote:
> > On Tuesday 29 June 2004 05:05 pm, Sebastian Haase wrote:
> > > Hi,
> > >
> > > Is this a bug?:
> > > >>> # (import numarray as na ; 'd' is a 3 dimensional array)
> > > >>> d.type()
> > >
> > > Float32
> > >
> > > >>> d[80, 136, 122]
> > >
> > > 80.3997039795
> > >
> > > >>> na.maximum.reduce(d[:,136, 122])
> > >
> > > 85.8426361084
> > >
> > > >>> na.maximum.reduce(d) [136, 122]
> > >
> > > 37.3658103943
> > >
> > > >>> na.maximum.reduce(d,0)[136, 122]
> > >
> > > 37.3658103943
> > >
> > > >>> na.maximum.reduce(d,1)[136, 122]
> > >
> > > Traceback (most recent call last):
> > >   File "<input>", line 1, in ?
> > > IndexError: Index out of range
> > >
> > > I was using  na.maximum.reduce(d)  to get a "pixelwise" maximum along Z
> > > (axis 0). But as seen above it does not get it right.  I then tried to
> > > reproduce
> > >
> > > this with some simple arrays, but here it works just fine:
> > > >>> a = na.arange(4*4*4)
> > > >>> a.shape=(4,4,4)
> > > >>> na.maximum.reduce(a)
> > >
> > > [[48 49 50 51]
> > >  [52 53 54 55]
> > >  [56 57 58 59]
> > >  [60 61 62 63]]
> > >
> > > >>> a = na.arange(4*4*4).astype(na.Float32)
> > > >>> a.shape=(4,4,4)
> > > >>> na.maximum.reduce(a)
> > >
> > > [[ 48.  49.  50.  51.]
> > >  [ 52.  53.  54.  55.]
> > >  [ 56.  57.  58.  59.]
> > >  [ 60.  61.  62.  63.]]
> > >
> > >
> > > Any hint ?
> > >
> > > Regards,
> > > Sebastian Haase
> >
> > Hi again,
> > I think the reason that no one responded to this is that it just sounds
> > to unbelievable ...
>
> This just slipped through the cracks for me.
>
> > Sorry for the missing piece of information, but 'd' is actually a
> > memmapped array !
> >
> > >>> d.info()
> >
> > class: <class 'numarray.numarraycore.NumArray'>
> > shape: (80, 150, 150)
> > strides: (90000, 600, 4)
> > byteoffset: 0
> > bytestride: 4
> > itemsize: 4
> > aligned: 1
> > contiguous: 1
> > data: <MemmapSlice of length:7290000 readonly>
> > byteorder: big
> > byteswap: 1
> > type: Float32
> >
> > >>> dd = d.copy()
> > >>> na.maximum.reduce(dd[:,136, 122])
> >
> > 85.8426361084
> >
> > >>> na.maximum.reduce(dd)[136, 122]
> >
> > 85.8426361084
> >
> >
> > Apparently we are using memmap so frequently now that I didn't even think
> > about that - which is good news for everyone, because it means that it
> > works (mostly).
> >
> > I just see that 'byteorder' is 'big' - I'm running this on an Intel Linux
> > PC. Could this be the problem?
>
> I think byteorder is a good guess at this point.  What version of Python
> and numarray are you using?

Python 2.2.1 (#1, Feb 28 2004, 00:52:10)
[GCC 2.95.4 20011002 (Debian prerelease)] on linux2

numarray 0.9 - from CVS on 2004-05-13.

Regards,
Sebastian Haase




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