[off topic] Re: [Numpy-discussion] numarray speed - PySequence_GetItem

Todd Miller jmiller at stsci.edu
Mon Jun 28 12:04:01 CDT 2004

On Mon, 2004-06-28 at 13:59, Chris Barker wrote:
> Sebastian Haase wrote:
> > BTW, from the profiling/timing I did you can tell that wxPyPlot actually plots 
> > 25000 data points in 0.1 secs - so it's _really_ fast ...
> Actually, it's probably not that fast, if you are timing on 
> Linux/wxGTK/X-Windows. X is asyncronous, so what you are timing is how 
> long it takes your program to tell X what to draw, but it may take 
> longer than that to actually draw it. However, what you are timing is 
> all the stuff that is effected by numarray/Numeric.
> I worked on part of the wxPython DC.DrawXXXList stuff, and I really 
> wanted a Numeric native version, but Robin really didn't want an 
> additional dependency. We discussed on this list a while back whether 
> you could compile against Numeric, but let people run without it, and 
> have it all work unless Someone actually used it. What makes that tricky 
> is that the functions that test whether a PyObject is a Numeric array 
> are in Numeric... but it could probably be done if you tried hard enough 
> (maybe include just that function in wxPython...) 

numarray-1.0 has two macros for dealing with this:  PyArray_Present()
and PyArray_isArray(obj).  The former (safely) determines that numarray
is installed, while the latter determines that numarray is installed and
that obj is a NumArray.  Both macros serve to guard sections of code
which make more extensive use of the numarray C-API to keep them from
segfaulting when numarray is not installed.  I think this would be easy
to do for Numeric as well.

One problem is that compiling a "numarray improved" extension requires
some portion of the numarray headers.  I refactored the numarray
includes so that a relatively simple set of 3 files can be used to
support the Numeric compatible interface (for numarray).  These could
either be included in core Python (with a successful PEP) or included in
interested packages.  This approach adds a small source code burden
somewhere,  but eliminates the requirement for users to have numarray
installed either to run or compile from source.

I'll send out the draft PEP later today.


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