#15196: Use mpmath for numerical evaluation of the beta function
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Reporter: eviatarbach | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-5.12
Component: numerical | Keywords:
Merged in: | Authors:
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Commit: | Dependencies:
Stopgaps: |
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Currently,
{{{
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 because GiNaC uses
`exp(log_gamma(-1.3)+log_gamma(-0.4)-log_gamma(-1.3-0.4))` to evaluate,
and `log_gamma` is broken for some input (see #12521). Using mpmath is
faster and avoids roundoff errors as well.
--
Ticket URL: <http://trac.sagemath.org/ticket/15196>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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