NumPy Slow ??

Travis Oliphant olipt at
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

Try setting the savespace property:


before you run that command to prevent this.  


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