#18210: numerical bug in incomplete gamma function
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Reporter: VivianePons | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.7
Component: symbolics | Resolution:
Keywords: sd67 | Merged in:
Authors: | Reviewers:
Report Upstream: Reported upstream. Developers | Work issues:
acknowledge bug. | Commit:
Branch: | Stopgaps:
Dependencies: |
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Comment (by rws):
Replying to [comment:22 buck]:
> @rws: Could you expand on the "two different bugs" and link them (and/or
create tickets for them)?
Okay, this ticket is the `(60,30)` bug from comment:13, i.e. `gamma(60,
30).numerical_approx()`. The other one is the fact that `gamma(25,14.5)`
and `CC(25).gamma_inc(14.5)`, which both use libpari, give
{{{
sage: CC(25).gamma_inc(14.5)
6.86802286928673e23
sage: gamma(25,14.5)
6.86802286928673e23
}}}
while
{{{
sage: pari('incgam(25, 14.5)')
6.15736429994994 E23
}}}
But then, we see also
{{{
sage: pari('incgam(60,30)')
-1.23084064495469 E74
sage: gamma(60,30).n()
-1.28306738270893e74
}}}
so there is a mismatch between the two interfaces, and the gp interface is
sometimes right where libpari is wrong.
> Also, could you explain why "because it uses the gp interface" would
obscure the negative-number return value?
Because the gp interface is sometimes right, apparently.
However, I don't think it useful to open two tickets as long as we don't
know if there really are two different bugs.
--
Ticket URL: <http://trac.sagemath.org/ticket/18210#comment:23>
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