Author: Sune Fischer
Date: 16:09:20 08/20/04
Go up one level in this thread
On August 20, 2004 at 13:03:28, Robert Hyatt wrote: >On August 20, 2004 at 12:05:59, Tom Kerrigan wrote: > >>On August 20, 2004 at 05:10:10, Tony Werten wrote: >> >>>On August 20, 2004 at 04:33:07, Tom Kerrigan wrote: >>> >>>>Now that AMD is selling two processors that are identical other than L2 cache >>>>size (Sempron has 256k, Athlon 64 has 512k) we have proof of Crafty's working >>>>set size: >>> >>>Or that it's >> 512 >>> >>>Basicly, this only proves that it's not between 256 and 512. >> >>That's not how cache works. By that rationale, you might as well not have any >>cache at all. See my reply to Bob above. >> >>-Tom > > >Tom, that is _exactly_ how cache works for some reference patterns. I don't believe this pattern is an accurate model for a chess engine. > See my >reply to you above. You don't yet have enough data to conclude anything about >the working set size. you might be right. You could definitely be wrong. At >present, there is no valid way to say, based on running on two small cache >processors. Then let's design a way :) For instance, say Crafty has a working set of 200 kB, try and add a dummy table of 1 kB to your working set by looping through this at every node. Now run the test again with increasing table sizes until you get hit with a big slowdown. That's when you start serious trash caching. Of course it assumes there's no trashing to begin with, but since Crafty is a pretty fast searcher I don't think there are any big cache issues. Granted there are a lot of small tables and they probably add to more than 256 kB, but I bet most of those are used only sparsely. -S.
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