Re: data structure for simulation

[Jaroslav Hajek]

On Thu, Mar 19, 2009 at 6:30 PM, Francesco Potorti` <address@hidden> wrote:
>>> 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).
>

That doesn't matter. The word heterogeneous was completely superfluous. Sorry.


>>Pipes, even FIFOs, don't generally work across NFS filesystems and the
>>like.
>
> 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
>>"lockfile".
>
> 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
>
> Sure
>
>>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 Potortě (ricercatore)        Voice: +39 050 315 3058 (op.2111)
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>



-- 
RNDr. Jaroslav Hajek
computing expert & GNU Octave developer
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic
url: www.highegg.matfyz.cz