Author: Jeremiah Penery
Date: 17:29:28 10/03/02
Go up one level in this thread
On October 03, 2002 at 19:39:27, Omid David wrote:
>On October 03, 2002 at 19:18:16, Jeremiah Penery wrote:
>>[D]8/7p/6pP/k4pP1/b1p1pP2/KpPpP3/1P1P4/7Q w - - 0 1
>>
>>Static evaluation is now 0 here. The solution is supposed to be Qd1 <bishop
>>move> {Kb5 Qh5!} Qxb3. The problem in solving this is that the evaluation after
>>the given line is negative for white, so it doesn't want to play the
>>'sacrifice'. But I consider it a good result that it knows this is a draw since
>>it can't make progress.
>>Normal Crafty 18.15 says near +5, while making the wrong move.
>>[D]4k3/8/1p1p4/pPpPp1p1/P1P1PpPp/5P1P/2BB4/K7 w
>>
>>This is the first problem position. It is evaluated statically as a draw, but
>>once White sacrifices its dark-squared bishop for one of black's pawns, it no
>>longer gets evaluated as a draw. No problem, right? Well, it keeps pushing it
>>back into the horizon:
>>
>> 6 0.01 6.39 1. Bxa5 bxa5 2. Kb2 Ke7 3. Kc3 Kd7
>> 6-> 0.02 6.39 1. Bxa5 bxa5 2. Kb2 Ke7 3. Kc3 Kd7
>> 7 0.02 6.50 1. Bxa5 bxa5 2. Kb2 Ke7 3. Kc3 Kd7
>> 4. Kd3
>> 7-> 0.03 6.50 1. Bxa5 bxa5 2. Kb2 Ke7 3. Kc3 Kd7
>> 4. Kd3
>> 8 0.03 -- 1. Bxa5
>> 8 0.03 0.00 1. Bxa5 bxa5 2. Kb2 Kd7 3. Bb3 Kc7
>> 4. Kc3 Kb6
>> 8 0.04 6.39 1. Ka2 Kd7 2. Kb2 Kc7 3. Bc3 Kb7 4.
>> Bxe5 dxe5
>> 8 0.05 6.50 1. Kb2 Kd7 2. Kc3 Kc7 3. Kd3 Kd7 4.
>> Bxa5 bxa5 <HT>
>> 8-> 0.05 6.50 1. Kb2 Kd7 2. Kc3 Kc7 3. Kd3 Kd7 4.
>> Bxa5 bxa5 <HT>
>> .......................................................
>> 19 2.69 6.56 1. Kb2 Kd7 2. Kc3 Kc7 3. Kd3 Kd7 4.
>> Bc3 Ke7 5. Bb3 Kd7 6. Be1 Kc7 7. Ba2
>> Kd7 8. Bc3 Ke7 9. Bxe5 dxe5 10. Bb3
>> 19-> 3.05 6.56 1. Kb2 Kd7 2. Kc3 Kc7 3. Kd3 Kd7 4.
>> Bc3 Ke7 5. Bb3 Kd7 6. Be1 Kc7 7. Ba2
>> Kd7 8. Bc3 Ke7 9. Bxe5 dxe5 10. Bb3
>>
>>No matter how deep I let it go, it always pushes the bishop sac into the last
>>couple of plies. Is there any way I can solve this problem?
>>Normal Crafty here says 7.77 static, and it doesn't have any captures in the
>>search as long as it goes, score stays around 8.26.
>>
>>Does anyone have more positions they'd like me to try, or has anyone else worked
>>on this kind of thing in their engine?
>
>
>My under-development engine, detects the positions you mentioned as draw based
>on static evaluation (seems that you have done something similar).
>
>However, for the first and last positions it fails to detect the draw. Your last
In the first position, my original method didn't detect a draw because the
A-File has no pawns and there is a rook/queen on the board. I now declare a
draw if all the pawns are blocked in a certain way, regardless of remaining
material - I figure the search can more easily find wins than it could find a
draw otherwise.
>position is really interesting; my program failed to detect the draw because of
>the very reason you mentioned.
I might try to work on this some, and come up with a solution if possible. But
right now I'm not sure how to do it.
>BTW, how much (in percentage or NPS) did the implemented draw detection slow
>down the engine?
AthlonXP 1600MHz is the hardware. I can get nearly a million NPS in bench from
normal Crafty with a very optimized compile, but my compiles are always quite a
bit slower for some reason, and I've implemented some probably costly functions.
The only difference in the two benches below is the blocked-position draw
detection.
With detection:
Crafty v18.15
White(1): bench
Running benchmark. . .
......
Total nodes: 69410117
Raw nodes per second: 708266
Total elapsed time: 98
SMP time-to-ply measurement: 6.530612
Without:
Crafty v18.15
White(1): bench
Running benchmark. . .
......
Total nodes: 69410117
Raw nodes per second: 715568
Total elapsed time: 97
SMP time-to-ply measurement: 6.597938
It's not the most scientific thing in the world, but I think it's safe to say
that it doesn't hurt performance all that much (especially compared to some
other things I've implemented in the past :). If there are some specific tests
you'd like me to run, I'd be happy to do so.
This page took 0.01 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.