Re: A case for C++11 in Octave

[Thomas Weber]

On Fri, Nov 14, 2014 at 05:14:03PM +0100, c. wrote:
> Hi Carnë,
> 
> On 14 Nov 2014, at 16:32, Carnë Draug <address@hidden> wrote:
> 
> > I understand that the reason for not making use of it is to avoid making
> > users in ancient systems to build a recent compiler.
> > While I appreciate the value of being able to build on older systems, I'd
> > like to believe that users on such systems are either more interested on
> > older versions of Octave (they avoid upgrades, after all they're still
> > running CentOS 5 and without EPEL), or are capable enough to build gcc
> > themselves.
> 
> Unfortunately the situation is not that simple.

I used to be in that situation, a long time ago on a Redhat-based
cluster. In order to build Octave, I first had to build a newer gcc
(installed version was 2.x something), than the ATLAS and some other
libraries and then Octave. So, this is not really a new situation for
Octave!

That said, if you decide to require a newer compiler, go the full way!
Take the *latest* available compiler and use all the features. As soon
as some people have to build a newer compiler, it does not matter if
they have to build 4.x or 4.x+1 - the work should be the same. 
Of course, having some documentation on how to build Octave and its
build-dependencies.

> Many recent HPC systems, as for example 
> http://www.hpc.cineca.it/hardware/plx are still using 
> quite old systems:
> 
>   "Welcome to PLX DataPlex Cluster @ CINECA  -  RedHat EL 5.6!"
> 
> and even if other versions of gcc than the default (which is 4.1.2)
> are available on that system, the most recent I managed to get
> installed there is 4.7 which does not yet implement the c++11 standard 
> completely.

Ask the administrators. If you are one of them, ask for help on some
other forums (maybe the GCC mailling lists, I don't know). This cluster
will run for a few years, so at some point in time the pressure for you
to provide a C++11 compiler will be so high that you have to give in ...

> Indeed I am able to compile gcc 4.9 myself and that's what I need to do on
> my laptop anyway, but doing so on the cluster at the system level involves a 
> lengthy and non trivial procedure.
> 
> I believe the same applies to more other scientific HPC or corporate systems 
> than 
> you would expect, so I don't think it is a good idea to drop backward 
> compatibility just yet ...

The pressue on these systems and their administrators will be mounting
anyways - Octave is hardly unique in willing to exploit the benefits of
C++11.

        Thomas