#17066: always simplify hypergeometric() when it's a polynomial
-------------------------------------+-------------------------------------
Reporter: rws | Owner:
Type: defect | Status: needs_review
Priority: major | Milestone: sage-6.4
Component: symbolics | Resolution:
Keywords: special, | Merged in:
functions, pFq, evaluation | Reviewers:
Authors: Ralf Stephan | Work issues:
Report Upstream: N/A | Commit:
Branch: | 55daf81080f46c54429e629b65e8049acfdb6d00
u/rws/work_around_mpmath_problem_with_hypergeometric___zeroes| Stopgaps:
Dependencies: |
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Comment (by mmezzarobba):
Replying to [comment:17 rws]:
> It appears the only solutions are
> A) restrict the range of parameters where ticket is applied
> B) do not simplify; just fix the evaluation problem
> C) rely on the user to supply needed precision; add warning
If (as you seem to say in your post to `sage-devel`) the result of the
ticket is that
{{{
sage: hypergeometric([1,-100],[3],x)
}}}
returns a polynomial while
{{{
sage: hypergeometric([1,-100],[3],0.7)
}}}
still calls a numerically stable evaluation algorithm, then I don't think
there is a problem. (Ideally, `
hypergeometric([1,-100],[3],x,hold=True).subs(x=0.7)` should also call the
numerically stable evaluation algorithm, though.)
What I was concerned about was that the implementation of `n()` for an
"atomic-looking" expression with dedicated numerical evaluation code would
end up using a numerically unstable formula ''internally'' without
adapting the precision or warning the user. I'm not saying such a
behaviour is an absolute no-go, but I do think it is something we should
avoid when possible.
--
Ticket URL: <http://trac.sagemath.org/ticket/17066#comment:19>
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