Author: Sune Fischer
Date: 01:57:56 08/22/04
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On August 21, 2004 at 21:14:57, Russell Reagan wrote: >On August 21, 2004 at 12:18:15, Sune Fischer wrote: > >>What you're saying here is basicly that Crafty has a working set that is much >>larger than 3 MB... > >You are not understanding what Bob is saying. He is not saying that Tom's >conclusion is wrong. He is saying that Tom's experiment does not *prove* Tom's >claim. Tom's conclusion may be correct. Tom's experiment may *support* his >conclusion. However, it doesn't *prove* his conclusion to be correct. Ehh Russel, what he says he is saying and what he is actually saying is two different things, IMO. If you read again you'll soon discover he seems very sure that he is blowing the cache continually and hence seems to claim there is no way it can fit in 256 kB. See for instance: "That has been _my_ point. I run through a _lot_ of such tables. And that tends to flush cache before something gets reused. A random probe into anything replaces N bytes (a cache line). IE on my PIV that is a 1 byte access replaces 128 bytes of cache in one chunk. On my dual xeons, that is 4096 cache lines. IE 4096 random accesses can completely flush cache. And I only accessed 4096 _bytes_ to do that." This postulate is just as "badly flawed" as Tom's, if anything Tom at least have tangible data to support his theory. Calling it badly flawed is an unnecessary exaggeration too IMO, it would have been more diplomatic to say something like "well your data is very interesting and certainly calls for further testing, at this stage however I'm not fully convinced you have sufficient data to make any solid conclusions....". Of course that's _not_ how we discuss things on this board ;) I certainly agree that it would appear that Crafty has a much bigger working set. Exactly how big this set is and in what way it gets used and re-used inside the program is very non-trivial to figure out IMO. I have a lot of tables too, but many of them are used scaresly like e.g. the king-pawn race table is only used in the far endgame, so I would not consider that as part of the working set under normal circumstances. Although Bob says he has "serialized" everything I'd rather not make too many assumptions about it but simply run a few tests. -S.
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