Author: Daniel Shawul
Date: 21:55:01 09/27/05
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On September 27, 2005 at 18:20:10, Tord Romstad wrote: >Hi Steve! > >On September 27, 2005 at 17:29:54, Steve Maughan wrote: > >>Interesting! Is there any particular reason for switching back to MTD other >>than curiosity? > >Yes. When I get some time for chess programming again (not any time soon, >I'm afraid) I want to give parallell search a try. I think it will be easier to >get >a parallell search working if I start with a very simple and minimalistic >search function. MTD is much easier to code than the other popular alpha >beta variants, and can be implemented in very few lines of code. It also >seems to be somewhat easier to parallellise, because all searches are done >with a null window. This means that it is never necessary to adjust the >bounds for other processors when one processor finds an improvement >to alpha or beta. Hi Tord If that is the only reason you are switching back, i think you might be disappointed. Especially if you use YBW you already get good enough bounds with the first move. daniel > >At least this is what I initially thought. Now I am no longer so sure. >MTD is easier to implement, but on the other hand it tends to be harder >to debug. When trying to write a parallell search, ease of debugging >might be more important than ease of implementation. > >>What are your findings? > >Nothing interesting yet, except that it is possible to implement >an MTD root driver, a search and a qsearch in less than 100 >lines of code. > >>Are you going to stick with MTD or go back to PVS? > >I will almost certainly go back to PVS sooner or later. It is >possible that there will be a public version with an MTD search >first, though. As far as I know, there is no modern, open >source chess engine of decent strength using MTD, which is >a shame. There really should be an implementation for >people to experiment with. > >>Have you started on your re-write of Glaurung? > >Yes, the MTD version is a complete re-write. It is still more >than 100 points weaker than Glaurung Mainz, though (which >isn't strange, considering that I have spent less than 10 hours >working on it). > >>I haven't come across that much literature on double bound transposition tables. >> I must say they intrigue me as I think the gap between the bounds could (in >>some cases) be used to shape the tree i.e. extend or prune. I plan to play >>around with double bounds with Monarch when I get the chance. > >Interesting, but in a PVS engine using two bounds I am afraid you >usually won't find many nodes where both bounds are actually used. > >Tord
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