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

Author: Sune Fischer

Date: 12:22:48 07/21/02

Go up one level in this thread


On July 21, 2002 at 14:38:38, Robert Hyatt wrote:

>On July 21, 2002 at 03:36:23, Sune Fischer wrote:
>
>>On July 21, 2002 at 03:29:51, Uri Blass wrote:
>>
>>>On July 21, 2002 at 03:16:40, Sune Fischer wrote:
>>>
>>>>On July 20, 2002 at 22:22:22, Robert Hyatt wrote:
>>>>
>>>>>On July 20, 2002 at 08:13:44, Gian-Carlo Pascutto wrote:
>>>>>
>>>>>>On July 20, 2002 at 08:04:01, Sune Fischer wrote:
>>>>>>
>>>>>>>I think it matters "a factor of 2".
>>>>>>>
>>>>>>>1) it helps you to prune
>>>>>>>2) you get better evaluation in the upper plies when you can return a score
>>>>>>>based on a deeper search.
>>>>>>>
>>>>>>>number one will show itself directly because you iterate deeper, the second one
>>>>>>>you don't "see", but it does improve depth along some branches in the same way.
>>>>>>
>>>>>>1) I get +- 10% hash hits (and less prunes) in typical middlegame. Not enough to
>>>>>>matter a factor of two (but I didnt check this so not 100% sure).
>>>>>>
>>>>>>2) Uh?
>>>>>>
>>>>>>--
>>>>>>GCP
>>>>>
>>>>>
>>>>>Run your program with a tiny hash and a deep search.  Then a big hash and
>>>>>a deep search.  In middlegame positions this will be at least a factor of
>>>>>2x.  Measure time to depth.  Small hash might take 4 minutes to get to depth
>>>>>12, then big hash will take around 2 minutes...
>>>>
>>>>You shouldn't measure time to ply, that would not give you the full benefit of
>>>>the hash. You should use time to find the right move.
>>>>
>>>>I have never seen the hash bring only a factor of 2, even in middlegame.
>>>>Last I tested I saw a mate in 5 being solved in 1/4 of the nodes with the hash.
>>>
>>>Do you use killer moves?
>>>
>>>I know that at least in version 1.17 you do not do it.
>>>
>>>Not using killer moves can increase the advantage
>>>of hash tables.
>>
>>That is right, for some reason they increased the size of the tree.
>>I found an error in my validate move rutine, perhaps it's time to try them
>>again:)
>>
>>But I still say time-to-ply is not the right way of testing, a "ply" is
>>meaningless in this regard.
>>
>>-S.
>
>OK.. A statement I can actually live with, finally.  :)
>
>You are correct in the tree searched with hashing and the tree searched without
>hashing have differences.
>
>1.  transpositions are eliminated, making the hash tree smaller.
>
>2.  move ordering is better with a hash tree.
>
>3.  The hash tree grafts information from one branch to another, making it
>potentially more accurate, for the same ply.
>
>But, since there is no real way to measure anything else (ie if you measure
>time to solution for both it could still be criticized in the same way since
>the hash tree will be a bit more accurate in addition to being faster...  So
>even comparing that is flawed...
>

Okay, there is an easier way then:)

Take a strong program, test its strength with and without hashing.
Now we know double speed is about 40-60 elo(*), compare that to the hash
gain/loss.

That should be far easier to measure, it would also include everything from
opening, mid to endgame making the whole discussion more realistic and less
academic.

As usual I doubt the experiment will be done, because we don't care about the
result as long as hashing == more rating!

foodnote:
(*) (depends on program, pool of players etc. but let's not get into that :)



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