[Coin-discuss] Multi-threaded mode for Cbc/Clp

[Ted Ralphs]

My guess is that it will work fine, but the easiest thing to do is try 
it! I guess you could also do it with a shell script, if this is all you 
are doing...

Cheers,

Ted

YANG YUAN wrote:
>  
> Hi Ted,
>  
> Thanks for the quick reply. Actually, i am not expecting Cbc itself to 
> run parallelly. In my case, I am coding my own algorithm, where Cbc is 
> called as a library for solving IPs. The parallelization is in my own 
> code, where i hope multiple processors are able to call Cbc and solve 
> multiple IPs concurrently. For instances:
>  
> #pragma omp parallel
> {
>    ......
> #pragma omp for
>       for ( ... ) {
>           ......
>           OsiSolverInterface *si;
>           si = new OsiCbcSolverInterface();
>           si->loadFromCoinModel(Parallel_model, true);
>           if(MIP)
>               si->branchAndBound();
>           else
>               si->initialSolve();
>           ......
>        }
> }
>  
> I have taken care of the private and public variables. Do you think it 
> will work parallelly as expected? or libCbc and libOsiCbc just can't be 
> called in this way.
>  
> Thanks -- yang
>  
> On 3/23/07, *Ted Ralphs* <tkralphs at lehigh.edu 
> <mailto:tkralphs at lehigh.edu>> wrote:
> 
>     Yang,
> 
>     OpenMP does not do any "automatic" parallelization. OpenMP is just a
>     standard set of compiler directives that tell an OpenMP-aware compiler
>     how to parallelize things. I don't see any OpenMP directives in Cbc
>     source code (they all start with "#pragma omp"), so it doesn't look like
>     it will run in parallel. In principle, it's not that difficult to
>     parallelize a tree search algorithm using OpenMP, but if you're not the
>     author of the code, that would probably make it significantly more
>     difficult. Also, the code has to be thread-safe to begin with. It
>     didn't
>     take me that long to convert SYMPHONY, only adding a few dozen lines of
>     code.
> 
>     Cheers,
> 
>     Ted
>     --
>     Dr. Ted Ralphs
>     Associate Professor
>     Industrial and Systems Engineering
>     Lehigh University
>     (610)758-4784
>     tkralphs at lehigh.edu <mailto:tkralphs at lehigh.edu>
>     www.lehigh.edu/~tkr2 <http://www.lehigh.edu/~tkr2>
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-- 
Dr. Ted Ralphs
Associate Professor
Industrial and Systems Engineering
Lehigh University
(610)758-4784
tkralphs at lehigh.edu
www.lehigh.edu/~tkr2