[Dune-devel] Compiler requirements

[Markus Blatt]

Hi,

I am actually a bit tired of this discussion, but anyway.

On Tue, Sep 19, 2017 at 09:13:40PM +0200, Christoph Grüninger wrote:
> having GCC 5.1 and CMake 3.1 seems reasonable to me.
> 
> Anything beyond that might be too progressive. Let's have an official
> vote. I like to hear the opinion of Markus and Robert. Further, we
> should ask our users. What kind of Red Hat is Alf and the OPM project
> currently using?
>

It is obvious that I am no big fan of progessively raising compiler
requirements (I still use Debian jessie). If we do this too fast, then
we loose some of our valuable downstream testers. I do think that this
is not in our best interest.

In OPM we are just aiming at officially supporting DUNE 2.5, because that
is the default version in Debian. As differences are not very large to the
upcoming 2.6 release we probably could use OPM for testing the release. If
the compiler requirements are increased, this might be too much work
and we will simply not do it.

Currently we are experiencing problems with the grid tests which are
using a bit too much TMP for my taste, and test things they should not
test. CpGrid has no codim-1 entities and does not always use the
interface/engine classes. Yet one test assumes that at
least one codim-1 entity exists for every element. The full geometry
interface for vertices is tested (jacobians, center, volume) and I am
not sure whether that makes
sense. https://github.com/OPM/opm-grid/pull/284 In our case we always
assumed using some of them are programming  errors. We cannot do that
anymore.

Redhat collaborators use gcc 4.9, but might be able to use newer ones
with Developer Tools. Ubuntu collaborators still hold us back on gcc
4.8, though. We do our testing on Debian stable and just switch to the
new one last week.

On the one hand I agree that supporting Ubuntu LTS for the full life
time (i.e. 14.04 with gcc 4.8(?) until 2019) might be overkill. On the
other hand if there is no good reason to switch why should we limit
the resource of human testers? If there is a good reason and we make
that clear then even some Ubuntu LTS users might be willing to jump to
newer versions.

So what are these good reasons again (besides the usual its new, its
cool, and I want to use it?

https://www.ubuntu.com/info/release-end-of-life
To the very least Ubuntu LTS should be supported during the hardware
maintainance period. Maybe even for 1 additional year. Same for Debian
stable version.

Just my 2 cents.

Markus