Author: Vincent Diepeveen
Date: 05:28:22 05/28/04
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On May 27, 2004 at 22:27:46, Slater Wold wrote: >On May 27, 2004 at 20:16:25, Bernardo Wesler wrote: > >>I wonder why some people say that HT is useless, and some other say it is good? >>But the main point at least for me, is to know what is HT really? Which are the >>pros and no-pros? Further details, welcome!! >>Thx in advance >>Dr Wesler > >I had a P4 (with HTing) and it was a neat feature for "free". It's tricky >though. It can help, and it can hinder. > >It can help in that 2 programs (different programs, and not chess programs) will >run better than on a 'standard' CPU. When I say better, I mean if they are both >using CPU time, they both will run faster than a 'standard' CPU. > >It can hinder a chess program, because a lot of people seem to think you can run >ponder=on matches; you cannot. Also, most SMP programs will get a 20%ish >speedup, but Crafty is now NUMA, and it can actually deteriate performace. So DIEP NUMA profits as you can see at aceshardware.com pretty good from HT. DIEP SMP not at all. This makes sense. NUMA versions run more local so worry less about what other processes do. >then you'd want to set CPUS=1. Well, then you're going to split it between the >physical and logical CPU, and it's going to run like crap. So then you have to >set your affnity to a single CPU, and remember to do that everytime. > >Told you it's tricky.
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