[Maxima-bugs] [ maxima-Bugs-3526359 ] gamma_incomplete(1/5, -32.0) not accurate

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Bugs item #3526359, was opened at 2012-05-13 10:50
Message generated for change (Comment added) made by rtoy
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Category: Lisp Core - Floating point
Group: None
>Status: Closed
>Resolution: Fixed
Priority: 5
Private: No
Submitted By: Raymond Toy (rtoy)
Assigned to: Nobody/Anonymous (nobody)
Summary: gamma_incomplete(1/5,-32.0) not accurate

Initial Comment:
gamma_incomplete(1/5,-32.0) is only accurate to about 2 digits.  

I think the problem is because maxima uses the series to evaluate this.  I think it works much better to use the relationship

gamma_incomplete(a,z) = gamma(a) - gamma_incomoplete_lower(a,z)


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>Comment By: Raymond Toy (rtoy)
Date: 2012-05-16 08:37

Message:
Fixed.  gamma_incomplete(1/5,-32) is accurate to about 15 digits now.

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