[r-t] Exhausted search spaces

Graham John graham at changeringing.co.uk
Sat Feb 6 00:22:27 UTC 2010

Simon wrote:

> If I leave hyperthreading enabled, then according
> to the documentation the processor is effectively
> divided in two, and SMC is confined to using just
> 50% of the processing capacity. Resulting in run
> times twice as long, I would have thought. 

It is not splitting the processor, it is duplicating part of it. It parallel
processes instructions to give a claimed 30% performance improvement. I ran
a SMC32 comparison on a hyperthreading processor in 2004 (possibly similar
to yours). The results for the "Full Monty" Cambridge S Major search were:-

1h49m single instance (but still with hyperthreading turned on)
2h37m running two searches simultaneously

So running two searches simultaneously was 28% quicker than running two

In summary, leave hyperthreading on - you can read your emails with one side
of the processor while running SMC32 at full speed on the other.



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