Don't use "long double" functions for Pynac

[jdemeyer]

There seems to be no reason to use the long double functions like sage_logl for Pynac. It interacts only with Python objects and Python's float corresponds to double in C.

CC: @rwst @embray

Component: cython

Author: Jeroen Demeyer

Branch/Commit: 20cdb45

Reviewer: Erik Bray, Ralf Stephan

Issue created by migration from https://trac.sagemath.org/ticket/20531

[jdemeyer]

Branch: u/jdemeyer/don_t_use__long_double__functions_for_pynac

[jdemeyer]

New commits:

491093c	Return 0 instead of NULL to fix compiler warning
b5ff931	Do not use "long double" functions for Pynac

[jdemeyer]

Commit: b5ff931

[embray]

comment:3

I don't know anything about Pynac but LGTM otherwise.

[rwst]

comment:4

LGTM too. I have put your real name in the Reviewer: field and set positive for you.

[rwst]

Reviewer: Erik Bray, Ralf Stephan

[kiwifb]

comment:5

Actually one the commit will fix a QA problem reported by portage in sage-on-gentoo. Quite happy about that.

[vbraun]

Changed branch from u/jdemeyer/don_t_use__long_double__functions_for_pynac to b5ff931

[vbraun]

Changed commit from b5ff931 to none

[vbraun]

comment:7

On OSX:

sage -t --long src/sage/symbolic/pynac.pyx
**********************************************************************
File "src/sage/symbolic/pynac.pyx", line 1795, in sage.symbolic.pynac.py_lgamma
Failed example:
    py_lgamma(4.r)
Expected:
    1.791759469228055
Got:
    1.7917594692280552
**********************************************************************
File "src/sage/symbolic/pynac.pyx", line 1797, in sage.symbolic.pynac.py_lgamma
Failed example:
    py_lgamma(4r)
Expected:
    1.791759469228055
Got:
    1.7917594692280552
**********************************************************************
1 item had failures:
   2 of   7 in sage.symbolic.pynac.py_lgamma

[jdemeyer]

comment:8

Interesting. So on OS X, (double)lgammal(4.0) is not the same as lgamma(4.0)

[jdemeyer]

comment:9

...which isn't that surprising perhaps, since lgamma() probably uses a less precise algorithm than lgammal(). Anyway, the error is still less than 1 ulp, so I will just add some # abs tol.

[jdemeyer]

Changed branch from b5ff931 to u/jdemeyer/b5ff9318c0bfa9720f6947f2fcdceb8f7fe2279d

[jdemeyer]

Commit: 20cdb45

[jdemeyer]

New commits:

491093c	Return 0 instead of NULL to fix compiler warning
b5ff931	Do not use "long double" functions for Pynac
20cdb45	Fix py_lgamma() doctests for OS X libm

[kiwifb]

comment:12

Trivially putting it back to positive review.

[vbraun]

Changed branch from u/jdemeyer/b5ff9318c0bfa9720f6947f2fcdceb8f7fe2279d to 20cdb45