Re: [Gomp-discuss] CIL representation ...

[Biagio Lucini]

Thanks Diego. I think there has been enough discussion today for writing
sort of a summary. I'll try to sort it out this evening and to post it
tomorrow (though expect delays! :-))

Biagio

On Wed, 12 Mar 2003, Diego Novillo wrote:

> On Wed, 2003-03-12 at 08:48, Biagio Lucini wrote:
> > On Wed, 12 Mar 2003, [iso-8859-1] Pop Sébastian wrote:
> >
> > > 12.6.7 defines volatile reads and writes that is exacltly what we have
> > > to deal with when OpenMP says shared variables: in other words variables
> > > visible across all threads.
> >
> > I think (tell me if I am wrong) that for a shared memory system (I believe
> > that we can't be "general" to the extend of tackling all the concurrent
> > model in one go) the general building blocks are
> > a) shared variables
> > b) private variables
> > c) locks
> > d) synchronisation
> >
> e) Memory coherency model.
>
> Variables may be shared across threads, but you may still not be able to
> see what other threads write.  This can be an advantage and a problem
> for the compiler.  (c) and (d) are the same thing.
>
> You also need to know the parallel model.  Having fork/join and parallel
> loops is more than enough to build most concurrent programs.
>
>
> > Questions: how does the actual optimising phase of gcc deals with Posix
> > Threads (if it does it at all)?
> >
> It doesn't.  When you use posix threads, it is your responsibility to
> implement thread safe functions.  That means using volatile variables,
> locking, etc.
>