Author: Sune Fischer
Date: 14:58:02 09/13/03
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On September 13, 2003 at 17:07:47, Robert Hyatt wrote: >On September 13, 2003 at 11:26:37, Nolan Denson wrote: > >>Hey Dan >> >>I decided to compile and give your crafty MPC a try. I am getting very good >>results but have notice something strange. I am not sure if this version is >>suppose to be able to take advantage of hyper threading ... but when i run the >>bench test my nps are better for a dual processor instead of a quad, But a >>strange things happens when actual game play starts. Using it as a Dual Xeon my >>nps (I compiled for multi-thread) 1536 nps avg, as a Quad the bench test is 1200 >>nps. But when actual game play starts the Dual stays about the same. But the >>Quad via Hyperthreading gets like 2100 nps ... Do you think is doing this on its >>own, or is this MPC Crafty Hyperthreading enable. If an one know the files that >>are involve ... i can make this MPC version truly Hyperthreading ...base on the >>results I am getting now .. if this is not Hyperthreading now ... i think once >>it is i should get around 2500-2600 nps. > > >Something is wrong. Do you really have SMT turned on? IE I have some dual >xeons here and hyper-threading definitely kicks the NPS up. Somewhere around >30% or so, for raw NPS... My dual 2.8 gets around 2.1M nodes per second on >the default setting bench command with mt=4 > >But be sure that on a dual with hyperthreading on, you do mt=4, _not_ mt=2. I have question, the way Crafty computes nps in a SMP run, is by summing up the nodes searched by the helper threads, right? As I understand it this should be more or less equivalent to the cpu-load figure, so it won't account for some of those nodes being lost to search inefficiency. For me, I'd like to look at the nps and know that this is "the speed I'm going". Unfortunately, I see no way of computing the exact nps, but it should be possible to compute an upper and lower bound on the effective nodes I think. When on an "allnode" we can add nodes to a counter when threads merge, let's call it lower_nodes, and when search is terminated prematurely or bounds gets adjusted we add to upper_nodes. Somewhere inbetween lies the effective node count, the count that would have been produced in a serial search, and some average can be used to calculate effective nps (enps?:). Let me know if I have I overlooked something. -S.
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