[SciPy-dev] Bessel functions from Boost

David Cournapeau david@ar.media.kyoto-u.ac...
Thu Feb 12 19:31:12 CST 2009


Pauli Virtanen wrote:
> Wed, 11 Feb 2009 03:31:30 +0900, David Cournapeau wrote:
>
> [clip]
>   
>> I started a branch, special_refactor. I added all the converted Boost
>> data set (the .ipp files to .csv), plus the small python script I used
>> to generate them. I started implementing the corresponding tests - but
>> this takes some time, because of all this template stuff which is
>> awkward to follow. The only thing to do is to find which function is
>> called for which test with which parameter - someone more familiar with
>> boost could to this much faster, I guess.
>>     
>
> I added a couple of more functions to the tests:
>
> They correctly point out that in 0.7.0:
>
> + The problems in Cephes's Iv (large argument), Yv (large order)
>   and Kn (large order)
>
> + Numpy's complex-valued `arcsinh` and `arctanh` can have large
>   relative errors (~1e-5) for small arguments (< eps)!
>
>   Loss of precision in the naive implementation, I'll bet.
>
> but they fail to spot the other known issues. But on the positive side,
> the `arcsinh` issue is the only new one that came up.
>
> One problem with these tests is that the data files are *huge*,
> they currently total ~ 7 Mb. Even compressed, or saved as .npy files,
> these would add ~ 2 Mb to the Scipy source tarball. So I'm not sure
> what to do with this...
>   

That's the reason why I started a branch - I did not know how it would
end up. I don't see an obvious answer to the problem: those are tests
for ~ 100 functions, so this means 20kb of compressed data/function on
average. Each test is two data points at least (x and f(x)), this means
around ~ 500 test points/function. That does not sound that big anymore.
Maybe we could have an option to split the dataset to make them separate
from the main tarball ?

I kept the data in .csv because I thought it would be nice to test for
double and float at least, and the gain using binary would not be that
huge anymore (it is also easier to use for tests outside the python
machinery),

cheers,

David


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