[Symphony] Symphony in a shared-memory architecture

[Aiko Vogelsang]

Hello everybody,

at first thanks for the answer! The selection of the max. active nodes works
fine.

But with the parallelization another problem occurred. If I use Symphony in
parallel I get a "Segmentation fault" after some calculations. If I use a
sequential version of Symphony for exactly the same problem (the only
difference in this case is "sym_set_int_param(env,  "max_active_nodes",
1);") everything looks like expected before (no failure). 

Secondly, if I get no segmentation fault (happens sometimes), the results of
the calculation in parallel differ from the sequential case. 

Is it possible that there's a still a race condition between the threads? If
so, I wouldn't understand it because I configured the solver for a parallel
environment. 

Does anybody have an idea what can be wrong here or where I could have a
look at? 

Again many thanks in advance for your support (I'm sorry to keep bothering
you with my problem)!

Best regards
Aiko


-----Ursprüngliche Nachricht-----
Von: Ted Ralphs [mailto:ted at Lehigh.EDU] 
Gesendet: Montag, 7. Februar 2011 17:30
An: Aiko Vogelsang
Cc: symphony at list.coin-or.org
Betreff: Re: [Symphony] Symphony in a shared-memory architecture

The parameter "max_active_nodes" controls how many threads are used
with OpenMP. To set that parameter through the API, do, e.g.,

sym_set_int_param(env,  "max_active_nodes", 8);

Let me know if that fixes your problem.

Cheers,

Ted

On Thu, Feb 3, 2011 at 5:12 AM, Aiko Vogelsang <aikovogelsang at gmx.de> wrote:
> Hello everybody,
>
> I've a question on how to use Symphony in a shared-memory architecture
again.
>
> Because of the hints I got last month I compiled Symphony with the option
"--enable-openmp". Everything works fine during compiling and installing.
> If I invoke the solver from the command line with the option "-p 4"
Symphony works in parallel (as I read in the manual).
>
> But if I include the header files and the library files of Symphony and
the related projects into my C++ project the solver still works in
sequential. I tried to insert some compiler (which is GCC 4.5) options but
nothing worked.
> According to my understanding I need an additional option compareable to
"-p 4" that would be inserted in the command line.
>
> If I could get a hint for this problem it would be very helpful! Many
thanks in advance!
>
> Best regards
> Aiko
>
> _______________________________________________
> Symphony mailing list
> Symphony at list.coin-or.org
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>



-- 
Dr. Ted Ralphs
Associate Professor, Lehigh University
(610) 628-1280
ted 'at' lehigh 'dot' edu
coral.ie.lehigh.edu/~ted