Author: Thomas Mayer
Date: 14:00:49 01/14/04
Go up one level in this thread
Hi Frank, seems that you haven't followed the discussion about hyperthreading lately. Well, I am no real expert in it, but some explanations: First of all: usually nps goes up by a factor of 2 on 2 processors - that is usual. But they produce some overhead so that a speedup of 1.7-1.8 is a good guess. (Some stated that they have above 2 - but I would say that sounds like phantasy... :) But we compare nps here, so: 2 threads on a Dual with hyperthreading DEACTIVATED (!) gets about double the nps then 1 thread on the same machine. When hyperthreadings is activated this is no longer true. Why ? Simple: it's always unclear on which processor a thread is running - that is also changing while it is running... so sometimes both threads run on the two virtual processors of one processor - it's clear that it is slower then. So running an engine with two threads on a Dual with hyperthreading enabled is nonsense - when you have enabled hyperthreading you should use ALL four available virtual processors. So your measurements are correct. Hint: You DO NOT HAVE 4 processors, you have only 2 in your machine - so you can't play with two Deep engines against each other - it would be absolutely unclear how much "effective" CPU-power they would get. Greets, Thomas P.S.: I hope that was understandable enough for you
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.