slots exceeding cpu cores

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FAMAS
Posts: 89
Joined: Fri Sep 16, 2016 6:30 pm

slots exceeding cpu cores

Post by FAMAS »

cpu slots can be added as much as can be in slots setting. would having more slots than the number of cores (5 slots in a dual core) cause any extra slowdown or will it be as if the performance is same but the slot work units are running in parallel as opposed to serial download and use?
bruce
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Re: slots exceeding cpu cores

Post by bruce »

True, but accepting the defaults won't do that.

When you alter any setting, you are taking responsibility for that choice.
If you don't understanding the implications of your change, don't make it.
ChristianVirtual
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Re: slots exceeding cpu cores

Post by ChristianVirtual »

Don’t do it, run it sequentially to avoid the overhead while task switching. Also the the Quick Return Bonus is for quick return. Your PPD overall will be higher as each assigned WU returns quicker.
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bruce
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Re: slots exceeding cpu cores

Post by bruce »

Under most circumstances, the default settings to a pretty good job of maximizing performance. The only common exception is if the installer sees 7 CPU threads available and it will need to be reduced to 6. It's adding one uniprocessor slot may or may not help.
FAMAS
Posts: 89
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Re: slots exceeding cpu cores

Post by FAMAS »

bruce wrote:True, but accepting the defaults won't do that.

When you alter any setting, you are taking responsibility for that choice.
If you don't understanding the implications of your change, don't make it.
christianvirtual gave the correct answer i think. the task switching in said test case in OP would cause a bottlenecking due to some performance being used to switch between tasks when 6 slots are run in cpu:2 system. if i am wrong, tell me. this feature is used by me to hoard work units in such a way as to i can continuously run them without connecting to network while also maintaining the timeout limit of the work units.
Joe_H
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Re: slots exceeding cpu cores

Post by Joe_H »

There is no scientific value to the folding project of running multiple slots overcommitting the available CPU cores. Not only will each WU take longer to process and return, delaying the issuing of the next Gen of that WU, the increase in processing time is not linear. So having 6 slots active when the system will only support one CPU:2 slot will result in processing times that are much more than 6 times as long.

There is also no scientific value in "hoarding" WU's. That delays progress on multiple runs of projects. At best it violates the spirit of the Best Practices published on the folding website - http://folding.stanford.edu/support/faq ... -practices.
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