Author: martin fierz
Date: 18:01:49 09/10/02
Go up one level in this thread
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 >>-- >>GCP
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