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Subject: Re: Robert, a little question ...

Author: Robert Hyatt

Date: 08:50:02 09/19/00

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On September 19, 2000 at 11:05:01, Frank Quisinsky wrote:

>On September 19, 2000 at 10:16:19, Robert Hyatt wrote:
>
>>On September 19, 2000 at 01:37:39, Frank Quisinsky wrote:
>>
>>>Hello,
>>>
>>>which program can solved 9/14 positions (I think no program can solved so many
>>>positions). Gandalf results, no 0 or 1 seconds results:
>>>
>>>01. 0578 seconds
>>>02. 0980 seconds
>>>03. 0386 seconds
>>>04. 0449 seconds
>>>05. 0205 seconds
>>>06. 0252 seconds
>>>07. 0711 seconds
>>>08. 0486 seconds
>>>09. ---
>>>10. ---
>>>11. 1151 seconds
>>>12. ---
>>>13. ---
>>>14. with the right move in ~ 32 minutes !
>>>
>>>BS2830 = 2667 ELO
>>>LCTII  = 2730 ELO
>>>
>>>In my eyes is Gandalf 4.32f the strongest program for analyses and maybe
>>>the stronges chess programm in the world ?
>>>
>>>Best
>>>Frank
>>
>>This has very little to do with how "strong" an engine is compared to others.
>>It only means it solves _this_ problem set faster.
>
>Yes this is right.
>
>In my News Ticker I have 250 Gandalf games with longer time controls and ponder
>!
>
>I am sure, I made a lot of tests with Gandalf in the last time. I think for
>tactical and middelgame analyses is Gandalf a very good engine. OK, I know not
>all commercial programs but I know a lof of results.
>
>BTW:
>Crafty played very good against the playing style from Gandalf !
>
>A questions to Crafty:
>I see that Crafty 17.13 is not faster then Crafty 17.11 but the new SMP version
>is faster.
>
>At the moment is the dual technic factor 1.8. Do you think that factor 1.9 or
>1.95 is possible ?

At times, 2.0 is possible.  But even 1.8 is not always going to happen.  I
even have a position or two where 2 processors are _slower_ than one.


>
>I have interest to get more information why is not more then factor 1.8
>possible. I think a very interesting message for my News Ticker because more and
>more persons have interest to buy a dual system an I think this is a interesting
>question about SMP.


Because move ordering is not perfect.  If you start a parallel search at a
ply where only one move needs to be searched, the extra processor is searching
a part of the tree that a single processor program would not search due to an
alpha/beta cutoff.  Since move ordering is not perfect, it is impossible to
accurately choose a position where all moves have to be searched, vs a position
where only one move needs to be searched.

As I have mentioned before, in Crafty, I am about 92% right.  That is, if I am
going to get a beta cutoff, 92% of the time it happens on the _first_ move
searched at a ply.  Unfortunately, that 8% where it is wrong is a real killer
to parallel performance.

Hence my 30% per processor overhead estimate.  1cpu = 1.0 speedup.  2cpu = 1.7
speedup, 3cpu = 2.4 speedup and 4 cpu = 3.1 speedup.  All rough averages, actual
numbers will vary wildly.




>
>See here (little zip file, Crafty bench results on dual and single PIII):
>http://amateurschach.in-trier.de/schach/download/sonstige/crafty_bench2.zip
>
>Frank



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