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Re: [HTCondor-users] Cluster Multithreading

I believe the capability you want is called MPI (Message Passing Interface).  This is an open C or Java API that lets you split processing across different Processes, much the way current languages do across Threads.  Just search the Condor documentation (or google condor mpi) and you'll find a lots of information.

I'm one of those Linux guys, but I have no reason to think there'd be any problem with Windows. 

By default, Condor schedules and manages down to the CPU core level, each of which is called a "Slot".  Just go through the tutorial to set up Condor and you'll see these in the condor_status output.  So, for example, my machines have 8 cores each and if I don't put specific restrictions in the job class ad, Condor will run up to 8 concurrent programs on each host.

What I can't say is whether there is any attempt at "isolation" - i.e., if a condor job is assigned to Slot #3, can we be sure it's only using one particular core on the machine or is that left up to the operating system?  Modern day programs typically use threading libraries that spawn lots of threads and the OS (windows and linux) generally tries to use as many of the cpu cores as it can get access to.  The internals to prevent this exist deep in the operating system, but for general-purpose computing it almost always turns out to be a bad idea trying to use them (i.e. the OS scheduler tends to make better decisions than a human programmer would).

My final caution is that MPI programming (actually multi-threaded, multi-host applications in general) can be very difficult to get working correctly, because there are unpredictable timing issues as the threads attempt to work together.  If you haven't done much coding with this paradigm, you need to make sure that the problem you are solving really can be split up into individual pieces that can run independently and then somehow collect together the final result you need.


On Sun, May 19, 2013 at 6:04 AM, Mostafa.B <bakhtvar@xxxxxxxxx> wrote:

I am interested in running a task in my PC and let it use the threads available in the cluster, I mean the CPU cores available in the cluster would appear as cores available in my PC from the the point of view of the task that I am going to run in my PC!
(I don't know whether this is called cluster Multithreading or not!)
is such thing possible with Condor?
if yes:
1. is it also available in Windows or this is also one of those amazing capabilities that is only possible with Linux.
2.How this is accomplished?

any other suggestions?



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David Hentchel

Performance Engineer


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