Author: Ralf Elvsén
Date: 13:12:42 08/29/99
Go up one level in this thread
On August 29, 1999 at 15:44:15, Ralf Elvsén wrote:
>On August 29, 1999 at 14:20:16, Mark Young wrote:
>
>>On August 29, 1999 at 13:30:20, Robert Hyatt wrote:
>>
>>>On August 29, 1999 at 12:36:18, Ralf Elvsén wrote:
>>>
>>>>This is a position from a game Hiarcs 7.32 - Crafty 16.6
>>>>Time 25 min/game, ChessBase interface etc, but that is not
>>>>important.
>>>>
>>>>6k1/1p4p1/p7/2Ppp3/1P6/P4KP1/5P1P/8 b - - 0 49
>>>>
>>>>What is interesting is that Crafty (black)
>>>>thinks the position is about even, with a score fluctuating
>>>>around equality, while Hiarcs for several plies
>>>>has realized that it has a won position and
>>>>has a score about +2 (an exchange of rooks has just
>>>>taken place some plies ago).
>>>>
>>>>I checked 16.6 as a winboard engine, also 16.16:
>>>>same result.
>>>>
>>>>This is a serious mis-evaluation of
>>>>the pawn structure since white easily can produce
>>>>passed pawns on both sides of the board, while
>>>>blacks connected free pawns can do nothing.
>>>>
>>>>Bob, maybe you want to look into this...
>>>>
>>>>
>>>>Regards, Ralf
>>>
>>>
>>>This is a bit speculative by hiarcs... ie I have seen it do this same sort
>>>of evaluation and be dead wrong as well...
>>>
>>>the only thing I don't evaluate at present is pawn majorities which turn into
>>>distant passed pawns. It is on my todo list, and I have some code written that
>>>does pretty well but is not ready for testing on the servers yet...
>>>
>>>My version of crafty (16.17 as released) thinks black is worse here, by about
>>>1/3 of a pawn... and as it advances pawns to make passed pawns, this gets
>>>worse. But there is always danger in these positions... and I only hope that
>>>I get more right than wrong... however, +2 here? Seems hard to fathom...
>>
>>I don't know if this is a case of specuation by Hiarcs or something else. I did
>>test some other programs on this position and they tend to agree with Hiarcs
>>7.32.
>>
>>5 min search.
>>
>>Crafty 16.13 Fritz 5 Junior 5 Hiarcs 6 Hiarcs 7.32
>>
>> +/= .43 +- 1.56 +- 2.07 +- 2.16 +- 2.23
>
>Not being a programmer myself I can only guess what is going on.
>If Crafty gives a big bonus to blacks passed pawns and doesn't
>consider whites potential, then that is incorrect in this case.
>However, I guess a program can give the "correct" score for
>different reasons:
>
>1. A correct evaluation of the pawn structure. I can
>imagine that it is not easy to include this in the
>evaluation function.
>
>2. The obvious fact that black is one pawn up is heavily
^^^^^
white
>weighted due to the fact that it is a pawn ending, where this
>usually is extremely important. This can however give
>erroneous results in other situations.
>
>Maybe one could do some testing on similar positions to
>find out how the programs "think". Unfortunately there
>are not many programmers who seem to have time to comment
>on things like this (understandably).
>Credit to Bob.
>
>Ralf
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