Stan Hoeppner <s...@hardwarefreak.com> writes: > Carl Johnson put forth on 1/13/2011 11:34 AM: > >> Processors Time (seconds) >> P1 66 >> P2 36 >> P3 25 >> P4 20 >> P5 20 >> P6 20 >> P7 20 >> P8 20 > > Your numbers bear out exactly what I predicted. Look at the decrease in run > time from 1 to 2, 2 to 3, and from 3 to 4 processes: > > #CPUs Decremental run time Fractional gain per CPU > 2 30s 1/2 > 3 11s 1/6th > 4 5s 1/13th > > You can clearly see the effects of serious memory contention when 3 cores are > pegged. Bringing the 4th core into the mix yields almost nothing compared to > three cores, cutting only 5 seconds from a 66 second run time.
I seem to be looking at it in a different way, because the numbers don't seem that much different that what I would expect. #CPUs time theoretical time-theoretical gain/CPU(theoretical) 1 66 2 36 66/2 = 33 36-33 = 3 (+9%) 1 -1/2 = 1/2 3 25 66/3 = 22 25-22 = 3 (+14%) 1/2-1/3 = 1/6 4 20 66/4 = 16.5 20-16.5 = 3.5 (+21%) 1/3-1/4 = 1/12 -- Carl Johnson ca...@peak.org -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/87ei8e2foa.fsf@oak.localnet
