[Numpy-discussion] A few comments (MDP conversion)

Nils Wagner nwagner at iam.uni-stuttgart.de
Thu Jul 13 10:42:24 CDT 2006

Pietro Berkes wrote:
> Dear numpys,
> a couple of weeks ago Tiziano and I completed the conversion of our data
> processing library MDP to numpy. We collected a few ideas and
> questions:
> - we found the convertcode.py module quite useful to perform a first,
>   low-level conversion. We had some problem when 'typecode' was
>   used as a keyword argument because the parser only converts
>   'typecode=' to 'dtype=' and skips the cases where there is an
>   additional space character before the equal sign ('typecode =').
>   Other names that might be easily converted are 'ArrayType' and
>   'NewAxis'.
> - some functions changed the columns/rows conventions ('cov', for
>   example). It would be really helpful to explicitly write this in the
>   list of necessary changes in the documentation.  It could be nice
>   to have the file 'convertcode.py' to print a warning every time one 
>   of this functions is used in the code.
> - the linalg functions svd, eig, inv, pinv, diag, and possibly
>   others perform an upcast, e.g. from 'f' to 'd'. This is apparently
>   because the litelapack module only wraps double precision routines.
>   Wouldn't it be more consistent to cast the results back to the
>   numerical type of the input? Otherwise, the user always has to take
>   care of the casting, which makes the use of single precision
>   arrays quite cumbersome.
> - we found a bug in the 'eig' function in the case the solution
>   is complex: in (linalg.py, line 269) 'Complex' should be 'w.dtype'
Did you file a ticket ?

It seems to be line 281 instead of 269. I am using latest svn.
BTW, in linalg.py in

def pinv:

 there is another Complex with capital C.


> We wondered whether it would be possible to obtain SVN write access in 
> orderto be able to fix this kind of issues by ourselves in the future.  
> We could also contribute docstrings for some of the functions.
> In general, we found the conversion to numpy quite straightforward
> and would like to thank you all for the great work!
> Cheers,
> Pietro Berkes and Tiziano Zito
> http://mdp-toolkit.sourceforge.net/
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