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cache alignment of tt
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Robert Hyatt



Joined: 27 Feb 2006
Posts: 17481
Location: Birmingham, AL

PostPost subject: Re: cache alignment of tt    Posted: Mon Mar 12, 2012 3:54 pm Reply to topic Reply with quote

rbarreira wrote:
bob wrote:

Pre-fetching is an unclear issue.


From what I've heard, it's quite clear that prefetch speeds up many engines. I guess Crafty might not benefit much from it since it doesn't access the tt in Qsearch?


Hard to say. I'd expect prefetch to work in the large majority of the cases, unless it is a speculative pre-fetch. For example, if you do a repetition test before a hash probe, there is a risk in pre-fetching the tt entry because you might not need it. And in the right kinds of positions, it will certainly hurt. Probably not when averaged over many games of course...

However, most prefetch at a sub-optimal place, such as at the top of search. Ideally you would prefetch right after making a move, where you just updated the hash signature. And you could perhaps improve that with a hash signature update done outside of make move, where the hash signature update is responsible for the prefetch, as early as is possible... But now you have changed the actual structure of the program and I have not noticed anyone going that far, although it is possible.

I'll try to run some tests to see if it helps today...
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Display posts from previous:   
Subject Author Date/Time
cache alignment of tt Daniel Shawul Sun Mar 11, 2012 10:22 pm
      Re: cache alignment of tt H.G.Muller Sun Mar 11, 2012 10:39 pm
            Re: cache alignment of tt Daniel Shawul Sun Mar 11, 2012 11:06 pm
      Re: cache alignment of tt Jon Dart Mon Mar 12, 2012 12:43 am
            Re: cache alignment of tt Daniel Shawul Mon Mar 12, 2012 2:53 am
            Re: cache alignment of tt Vincent Diepeveen Thu Mar 15, 2012 8:12 pm
      Re: cache alignment of tt Robert Purves Mon Mar 12, 2012 4:10 am
            Re: cache alignment of tt Daniel Shawul Mon Mar 12, 2012 4:49 am
      Re: cache alignment of tt Robert Hyatt Mon Mar 12, 2012 5:21 am
            Re: cache alignment of tt Ricardo Barreira Mon Mar 12, 2012 8:25 am
                  Re: cache alignment of tt Robert Hyatt Mon Mar 12, 2012 3:54 pm
                        Re: cache alignment of tt Alvaro Cardoso Tue Mar 13, 2012 12:33 am
                              Re: cache alignment of tt Robert Hyatt Thu Mar 15, 2012 2:15 pm
                                    Re: cache alignment of tt Rémi Coulom Thu Mar 15, 2012 4:42 pm
                                          Re: cache alignment of tt Robert Hyatt Thu Mar 15, 2012 5:03 pm
                                                Re: cache alignment of tt Daniel Shawul Thu Mar 15, 2012 5:08 pm
            Re: cache alignment of tt Daniel Shawul Mon Mar 12, 2012 12:49 pm
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