[SciPy-User] special.kv goes from 0 to nan for large numbers
Pauli Virtanen
pav at iki.fi
Mon Jan 23 19:59:51 EST 2012
Johann Cohen-Tanugi <johann.cohentanugi <at> gmail.com> writes:
[clip]
> In [4]: sp.kv(1./3.,1.08e+09)
> Out[4]: nan
[clip]
> I guess this has to dow with a cephes and big numbers.... Is it fixed on
> github already, or is it a known bug? Or is it a feature and not a bug?
No, it's not a known bug, please file a ticket.
The code for KV actually comes from Boost, so it's better quality than Cephes,
but apparently it wasn't perfect. There's no asymptotic expansion for KV, and it
seems the continued fraction or something else fails to converge in this limit.
--
Pauli Virtanen
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