Author: Vincent Diepeveen
Date: 10:16:58 09/11/02
Go up one level in this thread
On September 11, 2002 at 12:33:46, Robert Hyatt wrote: >On September 10, 2002 at 21:01:49, martin fierz wrote: > >>On September 10, 2002 at 20:45:43, Vincent Diepeveen wrote: >> >>>On September 10, 2002 at 18:06:01, Gian-Carlo Pascutto wrote: >>> >>>>On September 10, 2002 at 17:51:11, Vincent Diepeveen wrote: >>>> >>>>>On September 10, 2002 at 17:43:15, martin fierz wrote: >>>>> >>>>>>On September 10, 2002 at 17:18:24, Vincent Diepeveen wrote: >>>>>> >>>>>>>On September 10, 2002 at 17:10:38, martin fierz wrote: >>>>>>> >>>>>>>>On September 10, 2002 at 09:26:14, Eli Liang wrote: >>>>>>>> >>>>>>>>>(3) Reading Aske Plaat's search & re-search paper, it really seems like mtd(f) >>>>>>>>>is something of a magic bullet. But I note it seems that more programs don't >>>>>>>>>use it than do (for example Crafty). What is wrong with mtd(f) which Plaat >>>>>>>>>doesn't say? >>>>>>> >>>>>>>losing 1 bit is a problem for you? >>>>>> >>>>>>nope. losing 2 bytes is more like it... >>>>> >>>>>who stores a bound in 2 bytes? >>>>> >>>>>Why not in 1 bit? >>>> >>>>You want to store two actual values, not flags that indicate what >>>>kind of bound it is. >>> >>>did i implement it smarter then or what? >>>i used 2 bits in total. 'upperbound, lowerbound, truebound'. >>>the search result is based upon a single bound. So it IS the same, >>>it IS higher or it IS lower. >>> >>>What am i missing here? >> >>i'm doing the same. but in plaat's papers, he suggests you store both an upper >>bound, and a lower bound. the idea seems to be that since MTD potentially >>produces lots of researches, you could maybe use the additional information. at >>least that's what i think it's supposed to be. >>as an example, take a position somewhere in your search tree with true value 15. >>you do your first test with 0. you get e.g. lowerbound(p)=13. then you try 20. >>you get e.g. upperbound(p)=18. >>now, if your third test is for +10, and you get to this position again, you get >>a HT cutoff because of lowerbound(p)=13. the way you and i implemented it, we >>would only have the information upperbound(p)=18 in our table. which would give >>you no cutoff here. that's what i think this is about. >>however, there was this discussion about MTD always approaching the score from >>the same side. like that the sequence of tests i described 0,20,10 is not >>possible for certain MTD implementations. then you don't need to store 2 values, >>as bob pointed out. >> >>aloha >> martin >> > >It is a very "iffy" thing. If you can approach from the same side until the >last search, you will be ok. But that means you will approach the true score >more slowly if you have a "big" score swing. If you "bounce over" then all >the hash entries are going to be worthless. But then again, by bouncing over >you are also killing performance anyway since it is better to approach the true >score from the "upper side" for reasons already given. if you don't do binary jumps then obviously you always approach score for a ply P from the same direction. > > > >> >> >>>>-- >>>>GCP
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