Tuesday, June 28, 2022

Less is more

Last month I described my disappointment at the real-time performance I was getting in my million-digit Leyland-prime search. I have now done some testing on my wife's recently-acquired iMac, a 3.7 GHz 10-core Intel i9, slightly faster than my own two 3.6 GHz versions. Her computer was running only 4 of the million-digit search processes, because it was a replacement for a failing older 4-core iMac. Supplementing those processes by additional ones, I wanted to see how that would impact search time:

4 processes   4.2 hours   1.05 hours/process
5 processes   4.9 hours   0.98 hours/process
6 processes   5.9 hours   0.98 hours/process
7 processes   7.5 hours   1.07 hours/process
8 processes   9.7 hours   1.21 hours/process

In other words, on a 10-core iMac I can run 8 searches significantly faster simply by doing 4 at a time! Running 6 processes appears to be ideal.

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