#10050: numeric evaluation of polylog
---------------------------+------------------------------------------------
Reporter: burcin | Owner: burcin
Type: enhancement | Status: new
Priority: major | Milestone: sage-wishlist
Component: symbolics | Keywords:
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
---------------------------+------------------------------------------------
Changes (by burcin):
* keywords: beginner =>
Old description:
> Ginac includes an implementation of polylogarithms. The numeric methods
> of this implementation is commented out in the pynac source since it
> tries to call the `CLN` library directly, but the other parts should
> work.
>
> We should expose these functions (with a name other than `Li`).
>
> An example of how this can be done is available in #8864.
New description:
Numeric evaluation methods for the `polylog` function are commented out in
the pynac source since it tries to call the `CLN` library directly. The
calls to CLN should be replaced with their MPFR, etc. equivalents.
{{{
sage: polylog(2,1.0)
1/6*pi^2
sage: polylog(2,0.9)
polylog(2, 0.900000000000000)
}}}
This is also [https://bitbucket.org/burcin/pynac/issue/3/ pynac issue #3]
--
Comment:
Replying to [comment:1 zimmerma]:
> note that there are issues with the current polylog function:
> {{{
> sage: polylog(2,1.0)
> 1/6*pi^2
> sage: polylog(2,0.9)
> polylog(2, 0.900000000000000)
> }}}
> The first command should not evaluate symbolically, since the input 1.0
is a floating-point.
> The second command should evaluate numerically, like for example
{{{bessel_J(2,0.9)}}}.
>
> Should I open a separate ticket?
I was thinking of the other polylog like functions from
[https://bitbucket.org/burcin/pynac/src/tip/ginac/inifcns_nstdsums.cpp
ginac/inifcns_nstdsums.cpp] when I created this ticket. It seems even the
symbolic evaluation code for these is commented out, so this would require
quite a bit more work than I thought. I am removing the beginner keyword
and changing this ticket to only mention numeric evaluation of polylogs.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10050#comment:2>
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