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Follyx

not full CPU power during simulation

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Posted (edited)

I'm wondering: during the calculation of simulations without OpenCL, the single threads are not more used than about 45-50% in a 32Core Cpu. Why is that?

Edited by Follyx

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Posted (edited)

It's likely that some of the code can't be executed in parallel. Lots of things will affect this in Houdini like the type of objects, size, and complexity of the simulations. In theory you want a single core CPU with unlimited frequency. In reality it's not that simple.

https://en.wikipedia.org/wiki/Amdahl's_law

Edited by lukeiamyourfather

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Posted (edited)

so  would it be good to have a way in limiting the threads?.. Guess so

Edited by Follyx

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The code itself is likely limiting the number of threads adaptively so it doesn't completely tank performance. Most threaded code processes data in chunks. The chunk size might be quite small when divided by 32, so it reduces the number of threads to keep it larger. There's a non-trivial overhead for spawning and waiting on threads, and if you don't give a thread enough to do this starts dominating the cores as all you're doing is thread management. Plus there's usually some single-threaded code in between threaded code which can affect the %cpu reported, as it's averaged over the monitored interval.

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Posted (edited)

Ah, I see. Never interested so much in it cause its my first Workstation wit 64 Threads. But I'm sure I have to catch up a lot of more in deep knowledge. Specially with Houdini. As long I gave the jobs just to the renderfarm, well it just happens. But as you all know: new Hardware, new interests...

Thanks so far. But alwas open for further informations...

Edited by Follyx

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