Hello all,

> We quickly discussed the failing tests, and given that the option list
> used
> (https://bitbucket.org/ianhinder/cactusjenkins/raw/d7021a52bd83448db589b2346c43441682eecabb/build.cfg)
> is not using -ffast-math or -mmarch=native the working assumption is
> that the occurrence of the failures is due to to an updated OS and
> newer compiler. Erik asked if we had a docker container for the
> Jenkins test slave, which we were not sure (there is a docker image at
> https://bitbucket.org/ianhinder/et-jenkins-slave though it is not
> clear if this is the one used).

after the call of course I realized what may cause differences even
without -march=native or -ffast-math: the explicit vectorization in
thorn Vectors depends on the machine architecture so different hardware
(eg AVX2) will produce different vector code and thus different
answers. Though given the thorns affected (GRHydro and
SphericalHarmonicRecon) I doubt that it is the thorn's code itself but
rather eg McLachlan or the fftw library (for the PITTNull code). This
*may* cause differences though a different compiler *will* cause
differences (in particular a different Fortran compiler).