special.kn doesn't return inf (Trac #1783)

[scipy-gitbot]

Original ticket http://projects.scipy.org/scipy/ticket/1783 on 2012-12-01 by @josef-pkt, assigned to @pv.

While trying to see whether any of the k Bessel function works for large arguments, I found this.

kn doesn't return inf, instead returns the largest float (?)

>>> special.kn(50, 1e-1)
1.7976931348623157e+308
>>> special.kn(2000, 1e-1)
1.7976931348623157e+308





>>> special.kv(50, 1e-1)
3.4241477644707505e+127
>>> special.kv(2000, 1e-1)
inf

I got strange results, because I was taking logs of it:

>>> np.log(special.kv(1000, 1e-1))
inf
>>> np.log(special.kn(1000, 1e-1))
709.78271289338397





>>> scipy.__version__
'0.9.0'

[scipy-gitbot]

@josef-pkt wrote on 2012-12-01

python 2.6, windows 32 bit python (on 64 bit computer), in case it's relevant

[scipy-gitbot]

@pv wrote on 2012-12-01

PR #369

[scipy-gitbot]

@pv wrote on 2012-12-03

Fixed in d47bc968d

[scipy-gitbot]

Milestone changed to 0.12.0 by @pv on 2012-12-03