[Numpy-discussion] numpy.vectorize performance

Travis Oliphant oliphant.travis at ieee.org
Sat Jul 15 23:01:36 CDT 2006

Nick Fotopoulos wrote:
> Dear all,
> I often make use of numpy.vectorize to make programs read more like  
> the physics equations I write on paper.  numpy.vectorize is basically  
> a wrapper for numpy.frompyfunc.  Reading Travis's Scipy Book (mine is  
> dated Jan 6 2005) kind of suggests to me that it returns a full- 
> fledged ufunc exactly like built-in ufuncs.
> First, is this true? 
Yes, it is true.   But, it is a ufunc on Python object data-types.  It 
is calling the underlying Python function at every point in the loop.

>  Second, how is the performance?  i.e., are my  
> functions performing approximately as fast as they could be or would  
> they still gain a great deal of speed by rewriting it in C or some  
> other compiled python accelerator?
Absolutely the functions could be made faster to avoid the call back 
into Python at each evaluation stage.    I don't think it would be too 
hard to replace the function-call with something else that could be 
evaluated more quickly.  

But, this has not been done yet.

> As an aside, I've found the following function decorator to be  
> helpful for readability, and perhaps others will enjoy it or improve  
> upon it:

Thanks for the decorator.  This should be put on the www.scipy.org wiki.


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