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Re: data structure for simulation

From: Francesco Potorti`
Subject: Re: data structure for simulation
Date: Thu, 19 Mar 2009 18:30:30 +0100

>> The fact is, Montecarlo is a very particular and simple case of parallel
>> execution, which could be done by using Octave's popen command, fread,
>> fwrite and little else, all in a .m file without the help of external
>> libraries, taking Juroslav's parcellfun as a starting point.  If I am
>> not oversimplifying things...
>Parcellfun is easy to use - it should just work out of the box in
>standard Octave instalation. But since it relies on fork, it is really
>for multicore machines with shared memory. I have heard of systems
>where processes could be distributed amongst machines, but never seen
>any such thing. If you want to exploit a heterogeneous cluster, MPITB
>is probably the way to go.

No, the cluster is homogeneous (I think most clusters are like this).

>Pipes, even FIFOs, don't generally work across NFS filesystems and the

Ouch!  I should have known...

>      It is possible to use regular files for communication, but you
>need some NFS-safe locking mechanism. For instance, our cluster has

What about just a double buffer?  The writer creates a file, writes to
it and renames it, meaning that the reader can access it and then delete
it.  This should be good enough for Montecarlo.

>But using shared files will be surely slower than using MPI


>should only be recommended if your jobs are very expensive, so that
>even the file communication becomes negligible.

Yes, that's the case.

Ok, I'll see if I find a simple way to use these concepts or if I go
with MPI.  Thanks for the discussion.

Francesco Potortì (ricercatore)        Voice: +39 050 315 3058 (op.2111)
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