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by acadien 4086 days ago
Again I'm not sure if I agree or disagree with this. My hatred of MPI is only outweighed by the fact that I can use it... and my code works.

I think a large part of the inertia behind MPI is legacy code. Often the most complex part of HPC scientific codes is the parallel portion and the abstractions required to perform them (halo decomposition etc). I can't imagine there are too many grad students out there who are eager to re-write a scientific code in a new language that is unproven and requires developing a skill set that is not yet useful in industry (who in industry has ever heard of Chapel or Spark??). Not to mention that re-writing legacy codes means you're delaying from getting results. Its just a terrible situation to be in.
3 comments
sgt101 4086 days ago
I work in a medium sized telco, we have had Spark for prototypes for over a year and have now got a roadmap to put it in production.

I think Spark will totally displace map-reduce in the next 12 months (because it's got map reduce in it, but in memory).

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tormeh 4086 days ago
>who in industry has ever heard of Chapel

Chapel's made by Cray. If what you're saying is true then Cray's not done a very good job of advertising Chapel. God knows they have the capability to advertise properly.

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ljdursi 4086 days ago
Oh, sure. I don't think anyone should start rewriting old codes; but as new projects start, I think we have a lot more options out there than we did 10 years ago, and it's worth looking closely at them before starting, rather than defaulting to something. Especially since, once you start, you're probably pretty much locked into whatever you chose for a decade or so.
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sampo 4086 days ago
So, say you wanted to write a weather model, or engineering fluid mechanics model. Which options (besides MPI) you would look at?
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ljdursi 4086 days ago
Chapel has been used for incompressible moving-grid fluid dynamics, so it's certainly feasible. For that problem the result was ~33% the lines of code of the MPI version. There is a performance hit, but the issues are largely understood; if (say) a meteorological centre were to put its weight behind it, a lot of things could get done.

It's also pretty easy to see how UPC or co-array fortran (which is part of the standard now, so isn't going anywhere any time soon) would work. They'd fall closer to MPI in complexity and performance.

You couldn't plausibly do big 3d simulations in Spark today; that's way outside of what it was designed for. Now analysing the results, esp of a suite of runs, that might be interesting.

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