Author: Robert Hyatt
Date: 09:02:28 05/07/04
Go up one level in this thread
On May 07, 2004 at 11:53:29, Andreas Guettinger wrote: >On May 07, 2004 at 04:38:00, Vincent Diepeveen wrote: > >>On May 06, 2004 at 19:03:48, martin fierz wrote: >> >>>aloha! >>> >>>bob posted some crafty logfiles running a 24-position test set on his ftp site >>>(for anyone else crazy enough to repeat what i did: >>>ftp.cis.uab.edu/pub/hyatt/smpdata) >>> >>>these are logfiles of crafty running as single CPU, dual, or quad; on opterons. >>>i took the last completed ply on the single CPU set for each position (marked by >>>-> in the logfile, i hope...), wrote down the time to complete this ply, and did >>>this for all logfiles. there are 9 of these, 4 repeats for 2 and 4 CPUs. i >>>computed the speedup for time-to-finish-ply-X for each of the multi-CPU runs >>>with the following results: >>> >>>2 CPUs: >>>1.961 +- 0.093 >>>1.888 +- 0.074 >>>1.846 +- 0.078 >>>1.763 +- 0.084 >>> >>>4 CPUs: >>>3.15 +- 0.15 >>>3.29 +- 0.20 >>>3.06 +- 0.12 >>>3.19 +- 0.13 >>> >>>now, is there any meaning to this, and if yes, what? >>> >>>point #1 to make is that the numbers here are mutually consistent with each >>>other, given the error margins quoted. which should show those skeptical of this >>>statistical approach that it makes sense to do it this way, rather than to just >>>write "i measured speedup 3.1". >>> >>>point #2 is that the speedup on 4 CPUs on average is 3.17 in this test, which >>>might be one point for bob in the duel with vincent; although i suspect that the >>>speedup depends on the hardware architecture - i will leave this question to the >>>parallel computing experts though... >> >>Bob has tested the SMP version 1 cpu versus SMP version 2 or 4 cpus. The single >>cpu version of crafty is just hardly existing because of a stupid thread pointer >>which is a constant. Optimizing that crafty is 5% faster for sure in time single >>cpu at opteron. > >I don't understand that. What does that mean? > >regards >Andy Ever heard of "the fog of war"? This is "the fog of vincent". In crafty, I pass a pointer to a "TREE struct" around so that each thread can use a different struct for their local tree state. This is done even with mt=0 or when Crafty is compiled with no SMP support. Vincent claims it would speed Crafty up by 5% if the pointer were removed. That would be neat as it didn't slow me down 5% when I added the pointer. But that's irrelevant because Vincent has said so... IE everywhere that I now say tree->something such as: tree->node_count++; could be replaced by a non-pointer: node_count++; It doesn't cost 5%...
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.