#17066: always simplify hypergeometric() when it's a polynomial
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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: | 0e0fef65a021a9b0a9db30a2bc6d300ede68bf14
u/rws/work_around_mpmath_problem_with_hypergeometric___zeroes| Stopgaps:
Dependencies: |
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Comment (by kcrisman):
> > Just so I follow, what you are saying is that the polynomial (rational
function, I guess)
> No, it is really a polynomial—but one of degree 100, with large
coefficients that alternate in sign.
Oh, I misread some of the output in the example I tested - hard to see
where the dividing signs go :-) So it's the alternation that is the
cancellation problem, got it.
> > given will be ''correct'', but that substituting floating point
numbers are likely to be inaccurate unless carried out to a very high
degree of precision?
> Precisely. (Well, not necessarily a ''very'' high precision, but
probably something like 80-100 guard bits in my example.)
Anyway, 53 default yields madness, as we see in comment:16. Not good, but
I'm not sure what the "right" answer is; I'm leaning toward saying we
should ''not'' do this automatically, then, but making the simplification
a lot easier to find (which is probably already done in this ticket).
There are likely as many people using hg functions for numerics as for
symbolics, right?
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Ticket URL: <http://trac.sagemath.org/ticket/17066#comment:25>
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