Computer Chess Club Archives




Subject: Re: no more comments???

Author: Robert Hyatt

Date: 08:44:29 07/23/02

Go up one level in this thread

On July 23, 2002 at 11:00:26, Uri Blass wrote:

>On July 22, 2002 at 23:12:15, Robert Hyatt wrote:
>>On July 21, 2002 at 14:56:12, Robert Hyatt wrote:
>>>On July 21, 2002 at 14:54:18, Robert Hyatt wrote:
>>>>On July 21, 2002 at 01:29:38, Uri Blass wrote:
>>>>>On July 20, 2002 at 22:20:29, Robert Hyatt wrote:
>>>>>>On July 20, 2002 at 05:55:43, Uri Blass wrote:
>>>>>>>On July 20, 2002 at 05:47:38, Gian-Carlo Pascutto wrote:
>>>>>>>>On July 20, 2002 at 02:52:11, Uri Blass wrote:
>>>>>>>>>My question was not about comparing using hash tables
>>>>>>>>>and not using hash tables but about comparing using hash tables
>>>>>>>>>in the normal way and using hash tables
>>>>>>>>>for all purposes except pruning.
>>>>>>>>In the example given, the move ordering from hashtable is almost
>>>>>>>>irrelevant, so all the gains are due to pruning.
>>>>>>>I did not ask about single example from endgame but about
>>>>>>>the middle game or about rating improvement.
>>>>>>I gave you an answer of sorts.  Best case is fine 70.  3x as many plies.
>>>>>>Middlegame seems to be a factor of 2x in terms of time to reaching a specific
>>>>>>depth.  So a fraction of a ply.  So from early middlegame to endgame sees this
>>>>>>go from a fraction of a ply to (say) 30 additional plies...
>>>>>>The 30 is important.  It doesn't just happen in fine 70.  It happens in lots
>>>>>>of important king and pawn endings.
>>>>>I know that in simple endgames you can get big improvement thanks to using hash
>>>>>tables for pruning.
>>>>>I also know that you can get a factor of 2 in the middle game from hash tables
>>>>>when the comparison is between using hash tables and not using them.
>>>>>It did not answer my questions.
>>>>>Only Christophe answered them when he explained that I may get 10% speed
>>>>>improvement in the middle game from pruning.
>>>>OK... I will take my usual approach and simply give you _real_ data.
>>>>Three positions.  The first tactical, the second just a middlegame position
>>>>with no real tactics, the last an endgame (fine70).  All three searched with
>>>>normal hashing, and then using hashing as normal, but not allowing the hash
>>>>stuff to produce a fail high, fail low, or exact score.  It can still tell me
>>>>to avoid a null-move search.  The difference in times, then, is _totally_
>>>>dependent on using the hash scores only, as everything else is identical.
>>>>                 hashon         hashoff
>>>>Tactical         48 secs        78 secs
>>>>normal          118 secs       183 secs
>>>>fine 70           0 secs        58 secs
>>>>In fine 70, both searched to 18 plies.  hash on got right move (kb1
>>>>winning a pawn).  hash off did not get right move.
>>>>You can draw your own conclusions.  10% is obviously _way_ too low.  I
>>>>said roughly a factor of two, for middlegames, which is pretty close in
>>>>the first two.  In the last position we _know_ what hashing does.
>>>I should add, if you _really_ don't think that I answered your question, then
>>>maybe the question you actually _asked_ and the question you _meant_ to ask
>>>are not the same thing.  I believe my previous post shows that I _did_
>>>directly answer the question you asked.  _exactly_...
>>I find it interesting that I answer the question, get accused of not answering
>>the question, then I post _real_ data showing that I answered the question, and
>>the discussion stops cold...
>>why would that be???
>I thought that your data about being twice faster was about using big hash
>tables against small hash tables and not about using hash tables for pruning
>relative to using hash tables not for pruning.

Think about it for a minute.  If you use a tiny hash on a big search, what
are you doing?  Answer:  Using _no_ hash.  Using the "hash_move" is not a
big winner to me in terms of tree size.  What it lets me do is search faster
because I can try this move first without generating anything, and if I get
a cutoff, I get it with less work and go faster.  If I disable the hash move,
then killers and captures simply work better, and the overall difference is
not very large.  Except for the speed loss.

If you use history moves for ordering, hashing is not going to be a huge
win if all you get is move ordering from it.  If you do pruning, then the
question changes...

>I see the data and I may check later with movei how much speed improvement I can
>get from using hash to prune the tree.

This page took 0.19 seconds to execute

Last modified: Thu, 07 Jul 11 08:48:38 -0700

Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.