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Subject: Re: Null-Move: Difference between R = 2 and R = 3 in action

Author: Ricardo Gibert

Date: 20:12:28 07/19/02

Go up one level in this thread


On July 19, 2002 at 23:08:16, Robert Hyatt wrote:

>On July 19, 2002 at 22:15:31, Ricardo Gibert wrote:
>
>>On July 19, 2002 at 21:43:40, Robert Hyatt wrote:
>>
>>>On July 19, 2002 at 15:50:44, Uri Blass wrote:
>>>
>>>>On July 19, 2002 at 15:25:48, Christophe Theron wrote:
>>>>
>>>>>On July 18, 2002 at 12:14:10, Robert Hyatt wrote:
>>>>>
>>>>>>On July 18, 2002 at 05:58:56, Vincent Diepeveen wrote:
>>>>>>
>>>>>>>On July 17, 2002 at 13:18:40, Christophe Theron wrote:
>>>>>>>
>>>>>>>>On July 16, 2002 at 11:01:23, Vincent Diepeveen wrote:
>>>>>>>>
>>>>>>>>>On July 15, 2002 at 13:11:09, Christophe Theron wrote:
>>>>>>>>>
>>>>>>>>>>On July 15, 2002 at 08:37:34, Omid David wrote:
>>>>>>>>>>
>>>>>>>>>>>I don't think using double null-move is a good idea in practice, since in
>>>>>>>>>>>midgame the chance of zugzwang is negligible and thus it's superfluous (I doubt
>>>>>>>>>>>if even DIEP uses it). However the contribution of double null-move is that it
>>>>>>>>>>>gives legitimacy to the null-move pruning idea, proving that it _is_ a correct
>>>>>>>>>>>search method (anyway, no one doubts null-move nowadays).
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>Why does double null move prove that null move is a correct search method????
>>>>>>>>>>
>>>>>>>>>>Doing two null moves in a row means going back to standard search (a search not
>>>>>>>>>>involving an illegal move like null move is).
>>>>>>>>>>
>>>>>>>>>>I fail to see how it legitimates null move.
>>>>>>>>>
>>>>>>>>>Double nullmove legitimates (duh can't you use easier to spell words)
>>>>>>>>>itself, for the obvious reason that it is provable now that a search
>>>>>>>>>depth of n ply, where i may pick n, is going to solve any problem you
>>>>>>>>>give it.
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>OK, I see now.
>>>>>>>>
>>>>>>>>However, it is not true.
>>>>>>>>
>>>>>>>>Due to a nasty interaction with the hash table algorithms, just allowing 2 null
>>>>>>>>moves in a row will NOT solve any problem.
>>>>>>>
>>>>>>>What you refer to is a practical impossibility (assuming you have
>>>>>>>a efficient search) :
>>>>>>>
>>>>>>>  your assumption is that from a root position r
>>>>>>>  with transition of some moves to position p, side stm to move and
>>>>>>>  depthleft=d:
>>>>>>>
>>>>>>>  r ==> p(stm,d)
>>>>>>>
>>>>>>>  that you visit this position with properties that
>>>>>>>  before this move you have made 1 nullmove or less.
>>>>>>>
>>>>>>>  so ==> r , nullmove , p
>>>>>>>
>>>>>>>  Now a major problem for such an event to occur is that
>>>>>>>  after 1 nullmove, sides change the side to move.
>>>>>>
>>>>>>Why is this a problem?  IE in my case, position P reached thru a path
>>>>>>with a null-move and position P reached thru a path without null-move
>>>>>>are _unique_ positions...
>>>>>
>>>>>
>>>>>
>>>>>If so, your programs loses a lot of opportunities to prune because it detects
>>>>>less transpositions. But maybe it avoids some problems and is benefical in the
>>>>>end, I do not know.
>>>>
>>>>How much do programs earn by pruning based on hash tables?
>>>>
>>>>Today I do not use hash tables to prune the tree.
>>>>I am interested to know how much rating programs earn from
>>>>using hash tables to prune the tree.
>>>>
>>>>1)Did someone do the experiment of comparing the rating of
>>>>a chess program when hash tables are used only for things like order
>>>>of moves and the rating of the same program when hash tables are used also for
>>>>also to prune the tree.
>>>>
>>>>2)How much speed improvement do programs get in middle game
>>>>from pruning based on hash tables?
>>>>
>>>>Uri
>>>
>>>
>>>Try position fine 70 with and without.  Without you might get to depth 15
>>>or so.  With it you can reach depth 40.  A _significant_ gain...
>>
>>You're trying to drive Uri crazy aren't you?
>>
>>Did you really think Uri could not think of an example of a position where
>>having hash tables makes a significant difference?
>>
>>Do you really think being able to search a position like Fine 70 to a depth of
>>40 instead of 15 will make a difference in a programs playing strength?
>>
>>Don't you realize people are liable to react to such a reply as yours above as a
>>troll?
>>
>>Please try to be a bit more thoughtful.
>
>
>There was _no_ troll involved.  Point by point.
>
>fine 70 _is_ an important hash test. It represents a near-best-case for
>hashing.  Which is the best you can do.  It increases the search depth by
>at least a factor of 3x in terms of plies searched.
>
>Will that help the program?  Clearly in king and pawn endings I see 20+ ply
>searches _all_ the time.  And _that_ definitely helps for those positions where
>K+P endings are reached.
>
>But if you want to take a middlegame position, hashing is worth at least a
>factor of 2x based on tests I have run in the past.  I can always run them
>again.
>
>So to summarize, fine 70 was and is legitimate.  It _clearly_ shows that
>hashing makes a significant difference.  I hardly see why _your_ post wouldn't
>be considered a "troll" in fact.  As it attacks a legitimate point in a
>utterly simplistic and wrong context...
>
>Perhaps you should follow your own advice and try to be more thoughtful.
>_prior_ to posting???

I did. You didn't...again.



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