[Numpy-discussion] proposing a "beware of [as]matrix()" warning

Travis Oliphant oliphant@enthought....
Wed Apr 28 11:05:26 CDT 2010


On Apr 26, 2010, at 7:19 PM, David Warde-Farley wrote:

> Trying to debug code written by an undergrad working for a colleague  
> of
> mine who ported code over from MATLAB, I am seeing an ugly melange of
> matrix objects and ndarrays that are interacting poorly with each  
> other
> and various functions in SciPy/other libraries. In particular there  
> was
> a custom minimizer function that contained a line "a * b", that was
> receiving an Nx1 "matrix" and a N-length array and computing an outer
> product. Hence the unexpected 6 GB of memory usage and weird  
> results...

Overloading '*' and '**' while convenient does have consequences.   It  
would be nice if we could have a few more infix operators in Python to  
allow separation of  element-by-element calculations and "dot-product"  
calculations.

A proposal was made to allow "calling a NumPy array" to infer dot  
product:

a(b) is equivalent to dot(a,b)

a(b)(c) would be equivalent to dot(dot(a,b),c)

This seems rather reasonable.


While I don't have any spare cycles to push it forward and we are  
already far along on the NumPy to 3.0, I had wondered if we couldn't  
use the leverage of Python core developers wanting NumPy to be ported  
to Python 3 to actually add a few more infix operators to the language.

One of the problems of moving to Python 3.0 for many people is that  
there are not  "new features" to outweigh the hassle of moving.     
Having a few more infix operators would be a huge incentive to the  
NumPy community to move to Python 3.

Anybody willing to lead the charge with the Python developers?

-Travis





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