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

Author: Robert Hyatt

Date: 20:08:16 07/19/02

Go up one level in this thread


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???



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