[SciPy-Dev] Find points in delaunay triangulation : scipy.spatial vs. scipy.interpolation

[josef.pktd at gmail.com]

On Sun, May 13, 2012 at 10:57 AM, Pablo Winant <pablo.winant at gmail.com> wrote:
> Le 13/05/2012 08:44, josef.pktd at gmail.com a écrit :
>> On Sat, May 12, 2012 at 8:13 PM, Pablo Winant<pablo.winant at gmail.com>  wrote:
>>> Hi,
>>>
>>> I tried to use interpolation routines in scipy recently and I have found
>>> two slight performance issues
>>>
>>>   - The LinearNDInterpolation object implemented in cython requires a
>>> list of points and a list of values to be created. But is is not
>>> documented how to change the values of the interpolator without doing
>>> the mesh again. This is useful when one is solving the values of a
>>> function at the vertices of the mesh : one doesn't want to do the
>>> triangulation again and again. Maybe there could be a simple specific
>>> method to set the values in this case. In that case it would consist in
>>> changing the value of a property but it would be consistent with more
>>> general interpolation schemes.
>>>
>>> - I tried to use the delaunay object from scipy and noticed a strange
>>> thing: for a given set of coordinates it takes longer to get the indices
>>> of the triangles containing the points than it takes to perform the
>>> interpolation using LinearND object. This is puzzling since apparently
>>> the implementation of LinearND performs many calls to the qhull library
>>> to get this indices. Attached is a simple exampe demonstrating this anomaly.
>>>
>>> One last thing: I have written an interpolation object on sparse grids,
>>> using smolyak product of chebychev polynomials. It is written in pure
>>> python (vectorized) and licensed under the bsd license. Currently it
>>> lives in another library but I guess it would make more sense to have
>>> something like that in a more general scientific lib. Let me know if you
>>> are interested. (it is available there anyway:
>>> https://github.com/albop/dynare-python/tree/master/dolo/src/dolo/numeric: chebychev.py
>>> and smolyak.py)
>> Pablo,
>>
>> what is actually your license for dolo?
>
> It used to be GPL, but I changed it to BSD a while ago, precisely in
> order to integrate better with the python community.
> As I was using google-code at that time I switched to the new-bsd
> license which was the only bsd option.
> If I understand well, it is refered to as BSD-3.
>
> Now I must say I am a bit lost in this jungle, so I guess I would follow
> your suggestion if you say BSD-n is better.

A while ago I got confused about all these qualifiers for BSD (for
statsmodels), BSD with number is less ambiguous or easier to remember.
I don't think which BSD or which MIT doesn't matter as long as it is
clearly stated.

>
> There several other parts of the library which would fit better outside
> (such as a nonlinear solver with complementarity constraints) so it is
> important to me that the license makes a sensible relocation of the code
> possible.
>
>>
>> your license file is GPL
> Thank you for spotting that. I will need to properly do all these legal
> stuff once I am sure about the good license.
>> https://github.com/albop/dynare-python/blob/master/dolo/LICENSE
>> but setup.py says BSD and and I found another package using some of
>> your code as BSD-2
> Can you tell me which one it is ?

https://github.com/christophe-gouel/RECS/blob/master/LICENSE.txt
I only looked briefly, he uses your code to parse the model definition
files, otherwise matlab.
see bottom of this page https://github.com/christophe-gouel/RECS

I was just browsing after your link. There is some interesting code
and it would be good if we can share some of it.
I also didn't know about a python - octave bridge.
and was trying to see how easily we could create qnwnorm with scipy.

Cheers,

Josef

>
> Best,
>
> Pablo
>
>>
>> Thanks,
>>
>> Josef
>>
>>> Best regards,
>>>
>>> Pablo
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