Re: [Boost-mpi] Thread API

Subject: Re: [Boost-mpi] Thread API
From: Hal Finkel (hfinkel_at_[hidden])
Date: 2012-11-28 10:21:25

----- Original Message -----
> From: "Matthias Troyer" <troyer_at_[hidden]>
> To: "alain miniussi" <alain.miniussi_at_oca.eu>, "Discussion of Boost.MPI development" <boost-mpi_at_[hidden]>
> Sent: Wednesday, November 28, 2012 8:25:18 AM
> Subject: Re: [Boost-mpi] Thread API
> 
> Hi Alain,
> 
> 
> On Nov 27, 2012, at 5:11 PM, Alain O Miniussi <alain.miniussi_at_oca.eu>
> wrote:
> 
> > Hi,
> > 
> > I have a tentative patch that is supposed to  provide binding to
> > the MPI
> > thread API. What is the best way to have it reviewed ?
> 
> Thank you for your work. I have a few stylistic comments - shall I
> send them to you off-list, or shall we discuss them on our new
> mailing list?

If you don't mind, I'd prefer on-list reviews (even for stylistic matters). That way we can all benefit from your advice.

I also have a few comments:

+enum level {
+  /** Only one thread will execute. 
+   */
+  SINGLE     = MPI_THREAD_SINGLE,
+  /** Only main thread will do MPI calls.

I think that we should use lower-case enum constant names (single instead of SINGLE).

+  mt::level mt_level = mt::MULTIPLE;
+  boost::mpi::environment env(argc, argv, mt_level);
+  mt::level provided = env.thread_level();
+  std::cout << "Asked:" << mt_level << ", provided: " << provided << '\n';
+  BOOST_CHECK((provided >= mt::SINGLE && provided <= mt::MULTIPLE));

I have a lot of code that looks like this ;) -- but I think that it could be greatly simplified. How about if the environment constructor throws an exception if the provided level is less than the requested level. This way, in the common case where the program has no fall-back provisions, we don't accidentally continue under an invalid environment (many programs don't explicitly check the provided level -- and this obviously leads to odd behavior and crashes).

Thanks for working on this!

 -Hal

> 
> > It might be a ticket
> > buthttps://svn.boost.org/trac/boost/report/15the
> > referenced maintainer is Doug
> > (https://svn.boost.org/trac/boost/report/15)
> > and, probably since I have no userid in the tracker, I won't be
> > able to
> > change it.
> 
> I'll try to find out how to change it. Doug does not have time
> anymore.
> 
> > Just in case, there is a patch in attachment (against rev 81596 of
> > trunk).
> 
> 
> Thank you!
> 
> Matthias
> 
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-- 
Hal Finkel
Postdoctoral Appointee
Leadership Computing Facility
Argonne National Laboratory