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HPCE / hpce-2016-cw5

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Maximum scale for random walk? #31

Closed awai54st closed 7 years ago

awai54st commented 7 years ago

Hi,

May I ask what is the maximum scale you will require from us? At the moment me and my lab partner are trying on GPU and GPU memory is limited... So we wish to know the maximum scale we should expect.

Thank you

Best, awai54st

m8pple commented 7 years ago

I take a similar approach in the final perf tests as in the auto-tests (though different scripts). So there is a time-budget (though a fair bit longer), and then see how far it can get before running out of time.

The graph memory size scales as ~n^1.5, while the compute scales as n^2, so my back of the envelope calculations were that you wouldn't run out of memory n=400000 or so.

If you're trading off space for isolation (e.g. private arrays per work-item) you may hit that point earlier. Something to try is to allow sharing of arrays between work-items using atomics, or to not launch the entire grid at once (send through batches from software).