[gentoo-science] [sage-on-gentoo] sage is not blocking gmpy anymore in sage 6.5 and 9999

[François Bissey]

Hi,

Almost 2 years ago almost to the day I included a line blocking the
installation of gmpy alongside sage in the sage ebuild.
This was done because I had regular reports of people breaking
sympy when both were installed at the same time - ultimately
sage was broken too but the big symptom was an un-ability to
build/reinstall sympy.

The fundamental issue seems to have fixed in mpmath upstream
so I lift the restriction today.

But it will be back if new issue are discovered.

A quick note for people wanting to use gmpy as the backend
for mpmath/sympy. By default if both gmpy and sage are installed
mpmath will use sage as its backend for arbitrary precision
computation. This is a runtime behavior that cannot be altered
by useflags. If you want to use gmpy over sage as the backend
you need to define the variable MPMATH_NOSAGE (its value is not
checked, just its existence). Similarly there is a MPMATH_NOGMPY
check.
People interested in the mechanics of the backend should look at
/usr/lib64/python2.7/site-packages/mpmath/libmp/backend.py

Cheers,
Francois