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[Octave-bug-tracker] [bug #48307] sinc loses precision for large argumen
From: |
Colin Macdonald |
Subject: |
[Octave-bug-tracker] [bug #48307] sinc loses precision for large arguments |
Date: |
Tue, 5 Jul 2016 07:27:35 +0000 (UTC) |
User-agent: |
Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:47.0) Gecko/20100101 Firefox/47.0 |
Follow-up Comment #28, bug #48307 (project octave):
I looked more carefully at bessel functions: my example in #48316 is a bit
flawed: it only uses integer inputs. The relative error is much larger for
nearby non-integer inputs. Maybe my expectations really are out-of-line with
common practice here! I apologize for the tone of my debate.
My reading about other tools:
[Zhang and Jin 1996] (Standard special function reference). For jn(x), they
simply compute sin(x)/x in double precision for j0(x). SciPy then uses this
algorithm via the fortran code "specfun". For this reason, scipy's j0(pi*x)
agrees with Octave's sinc(z).
NR: for jn(x), they call their regular besselj function and scale with
sqrt(1/x)---the formula I mentioned below.
Matlab: seems to use sin(x)/x (b/c results match Octave's)
Boost: uses sin(x)/x for j0 and otherwise uses besselj.
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- [Octave-bug-tracker] [bug #48307] sinc loses precision for large arguments, (continued)
- [Octave-bug-tracker] [bug #48307] sinc loses precision for large arguments, Marco Caliari, 2016/07/04
- [Octave-bug-tracker] [bug #48307] sinc loses precision for large arguments, Dan Sebald, 2016/07/04
- [Octave-bug-tracker] [bug #48307] sinc loses precision for large arguments, Lachlan Andrew, 2016/07/04
- [Octave-bug-tracker] [bug #48307] sinc loses precision for large arguments, Dan Sebald, 2016/07/05
- [Octave-bug-tracker] [bug #48307] sinc loses precision for large arguments, Colin Macdonald, 2016/07/05
- [Octave-bug-tracker] [bug #48307] sinc loses precision for large arguments, Colin Macdonald, 2016/07/05
- [Octave-bug-tracker] [bug #48307] sinc loses precision for large arguments, Colin Macdonald, 2016/07/05
- [Octave-bug-tracker] [bug #48307] sinc loses precision for large arguments, Lachlan Andrew, 2016/07/05
- [Octave-bug-tracker] [bug #48307] sinc loses precision for large arguments, Dan Sebald, 2016/07/05
- [Octave-bug-tracker] [bug #48307] sinc loses precision for large arguments, Dan Sebald, 2016/07/05
- [Octave-bug-tracker] [bug #48307] sinc loses precision for large arguments,
Colin Macdonald <=
- [Octave-bug-tracker] [bug #48307] sinc loses precision for large arguments, Marco Caliari, 2016/07/05
- [Octave-bug-tracker] [bug #48307] sinc loses precision for large arguments, Dan Sebald, 2016/07/05
- [Octave-bug-tracker] [bug #48307] sinc loses precision for large arguments, Colin Macdonald, 2016/07/06