Subject: Re: [boost] [Fibers] Performance
From: Thomas Heller (thom.heller_at_[hidden])
Date: 2014-01-16 12:19:36
Am 16.01.2014 17:57 schrieb "Giovanni Piero Deretta" <gpderetta_at_[hidden]>:
> On Thu, Jan 16, 2014 at 4:44 PM, Hartmut Kaiser <hartmut.kaiser_at_[hidden]
> > > > > Now, if we were talking about hundreds of thousands of threads or
> > > > > milions of threads, it would be interesting to see numbers for
> > > > > 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
> > > > (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
> > on the top 500 list  (Tianhe-2 ) has 3120000 cores (in 16,000
> > 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
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 .
> -- gpd
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