NumPy Slow ??

Travis Oliphant olipt at mayo.edu
Tue Sep 19 00:17:27 CEST 2000


> Why is it that this line take ~30 sec to execute on a 500 MHz pentium III
> 128Meg RAM ?
> 
> data1 = choose(greater(data,z2),(data,z2))
> 
> where data is a 2048x2080 array of float and z2 is a float.
> 
> I thought that NumPy functions where written in C for faster execution. Or
> maybe that I'm wrong and this is fast execution?

You are very likely creating a new 2048x2080 array of doubles (not floats) 
with the comparison to a float (a Python float object is interpreted by
NumPy as a double). Some of the time is spent copying creating that new
array.

Try setting the savespace property:

data.savespace(1)

before you run that command to prevent this.  

-Travis







More information about the Python-list mailing list