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NSC Ray trace somehow slower with more cores?


William Oak
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Hello,

So I’ve been trying to optimise the processing speed for a macro where I test a large number of configurations. I initially did the usual-maximising # of cores, reduced analysis rays to minimum viable (about 1000, which is enough for total power)), but the process was still very long.

 

So then I re-checked the raytrace and somehow...fewer cores was faster? By a good order of magnitude. I am intensely confused by this result.

From googling a little, it might be an issue that shifting data between cores is more time-consuming than the individual processes. And with a larger amount of rays (10^6), multicore seems to be substantially faster. The result I’ve observed is confusing however.

Best answer by Mark.Nicholson

The thing to remember is that if ‘All Cores’ was always better, they wouldn’t give you an option to get the number. All Cores is the default setting but it can be improved upon, particularly as the number of rays/core goes down, as the overhead of launching, managing and receiving thread data becomes significant compared to the ray tracing.

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  • July 20, 2023

Mark.Nicholson
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The thing to remember is that if ‘All Cores’ was always better, they wouldn’t give you an option to get the number. All Cores is the default setting but it can be improved upon, particularly as the number of rays/core goes down, as the overhead of launching, managing and receiving thread data becomes significant compared to the ray tracing.


William Oak
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  • July 20, 2023
Mark.Nicholson wrote:

The thing to remember is that if ‘All Cores’ was always better, they wouldn’t give you an option to get the number. All Cores is the default setting but it can be improved upon, particularly as the number of rays/core goes down, as the overhead of launching, managing and receiving thread data becomes significant compared to the ray tracing.

That certainly seems to be the case. Thanks!

 

 


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