#10239: Bessel method forces bessel_Y to use pari algorithm
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Reporter: jvkersch | Owner: jason, jkantor
Type: defect | Status: needs_work
Priority: major | Milestone: sage-4.6.1
Component: numerical | Keywords: functions, bessel, pari
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Changes (by jvkersch):
* status: new => needs_work
Comment:
The patch seems to work well. The `Bessel` method now behaves as
intended, and the patch also addresses some other inconsistencies in the
code (checking the precision for the scipy code, and some documentation
issues).
There is one doctest that fails on my machine (64bit macbook pro, sage
4.6):
{{{
sage: Bessel(6, algorithm="scipy")(pi)
Expected:
0.0145459669825000 + 5.34392507678000e-18*I
Got:
0.0145459669825000 + 5.34410157169000e-18*I
}}}
This looks like inevitable round-off error in the complex part. Can we
hit this doctest with the `#random` tag or is there a more subtle way of
dealing with this? IMHO, this is also a bug in scipy: for real input, the
Bessel functions of the first and second kind should be exactly real, not
up to some small complex drift. This will cause all sorts of problems
with plotting, etc.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10239#comment:3>
Sage <http://www.sagemath.org>
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