Hi,
I've been a bit busy lately, but I should have time to work more on this issue on next week.
18.02.2015, 18:47, "Michael Ferguson" <[email protected]>:
Hi John -I just wanted to add a little to this exchange. You were talking about your custom distribution and you said:My implementation isn't quite as efficient as I'd like, though I'll see what kind of improvement some caching will bring...You might be interested to try the --cache-remote option when compiling (which should work with GASNet and FIFO tasking, and maybe with qthreads). That will activate a runtime feature that caches remote data. This feature might be able to improve your distribution's performance without a lot of extra work - or give you an idea how much you can reduce communication with privatization/manual caching in the distribution implementation. If you try it - please let me know how it goes since this feature is still pretty new.
I actually already did implement some caching and they improved performance significantly. But I can try if that option brings some further improvement, though I doubt further caching would help significantly unless I have missed something very obvious... Would you clarify should I pass that option while compiling chapel or just my own program? I guess that --fast flag would also help.
As another note, you mentioned a desire to check the load balance when running on a single machine (vs on a cluster). In that situation, be sure to carefully measure something that will be the same in a cluster run. In particular, runtime is not a good thing to measure in this situation because you'll probably be oversubscribing the single machine and each task will slow down (because tasks/threads will be multiplexed to fewer processors). However, things like # of array elements processed on each locale or the communication counts are good things to measure that should be the same when you execute on a real cluster.
Hmm, I have to think about that. I needed a mechanism to measure execution time anyway, to that would have been easily available, that's why I though of that first. But number of elements per locale should be very easy to gather.
If you'd like help with gathering communication counts - just ask.
Sure, I would appreciate any help :) Though some more work on the code is required before. What kind of hardware you have access to?
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