Re: [boost] [Fibers] Performance

Am 16.01.2014 17:57 schrieb "Giovanni Piero Deretta" :

On Thu, Jan 16, 2014 at 4:44 PM, Hartmut Kaiser

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Now, if we were talking about hundreds of thousands of threads or milions of threads, it would be interesting to see numbers for

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threads and fibers...

FWIW, the use cases I'm seeing (and trust me those are very commonplace at least in scientific computing) involve not just hundreds or thousands of threads, but hundreds of millions of

both threads

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(billions of threads a couple of years from now).

On a single machine? That would be impressive!

Well, it depends on the size of the machine, doesn't it? The no. 1 machine on the top 500 list [1] (Tianhe-2 [2]) has 3120000 cores (in 16,000 compute nodes).

Oh, right!

Do they usually present a single OS image to the application? I.e. do all the cores share a single memory address space or nodes communicate via message passing (MPI I presume)? std::thread-like scaling is relevant for the first case, less so for the later.

If you decide to program with MPI that's certainly true. However HPX[1] provides the ability to spawn threads remotely, completely embedded in a standard conforming API. For those remote procedure calls a small overhead is crucial in order to efficiently utilize your whole machine. We demonstrated the capability to do exactly that [2]. [1]: http://stellar.cct.lsu.edu [2]: http://stellar.cct.lsu.edu/pubs/scala13.pdf

-- gpd

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