[Numpy-discussion] ScientificPython with numarray support

konrad.hinsen at laposte.net konrad.hinsen at laposte.net
Sun Jan 16 03:29:20 CST 2005


On 15.01.2005, at 02:23, Sebastian Haase wrote:

> I thought it should be there.
> Is the code / algorithm about similar to what Konrad has in Scientific  
> ?
>
I don't know exactly what's in SciPy, but it's probably a variant of  
Levenberg-Marquart, just like in Scientific Python.

However, there is one peculiarity of my implementation which is  
probably not shared by the SciPy one, and which is the cause of the  
incompatibility with numarray: the use of automatic derivatives in the  
linearization of the model. Most implementations use numerical  
differentiation. Automatic derivatives have the advantage of removing  
one numerical issue and one critical parameter (the differentiation  
step size), at the cost of somewhat limiting the applicability (the  
model must be expressed as an analytical function of the parameters)  
and of requiring a NumPy feature that numarray doesn't have (yet?).

BTW, that feature was recenly discussed here: it is the possibility to  
apply the maths functions to objects of arbitrary type. This makes it  
possible to apply the same numerical code to numbers and arrays but  
also to the  number-like objects that are used for automatic  
derivatives.

Konrad.
--

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Konrad Hinsen
Laboratoire Leon Brillouin, CEA Saclay,
91191 Gif-sur-Yvette Cedex, France
Tel.: +33-1 69 08 79 25
Fax: +33-1 69 08 82 61
E-Mail: hinsen at llb.saclay.cea.fr
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