#12521: evaluate log gamma for complex input
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Reporter: kcrisman | Owner: AlexGhitza
Type: defect | Status: new
Priority: major | Milestone: sage-5.6
Component: basic arithmetic | Resolution:
Keywords: lgamma log_gamma | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Comment (by eviatarbach):
There is a related issue with the beta function:
{{{
sage: beta(-1.3,-0.4)
NaN
sage: (gamma(-1.3) * gamma(-0.4)) / gamma(-1.3 - 0.4) # expected
functionality
-4.92909641669610
}}}
This is presumably because GiNaC uses
`exp(log_gamma(-1.3)+log_gamma(-0.4)-log_gamma(-1.3-0.4))` to evaluate,
and `gamma(-0.4)` is negative. I'm confused as to why it works fine in the
GiNaC interactive shell though.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12521#comment:6>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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