Hi All,
My engine displays an asymmetrical evaluation with search depth:
1 6 0 B4A3 -16cp
2 84 0 A6D6 H7H8 -57cp
3 220 0 A6XF6 G7XF6 B4B3 -18cp
4 2908 0 A6A2 H7G8 A2XE2 G8F7 -59cp
5 10030 0 A6A2 E2F4 B4B3 G7G5 A2A7 -21cp
6 20814 0 A6A2E2F4 A2D2 H7G8 D2H2 G8F7 -65cp
7 188578 4 A6E6 E2F4 E6E4 F4G2 B4C5 G7G5 E4A4 -23cp
8 1146981 19 A6A2 E2F4 B4XB5 H7H6 B5C4 H4H3 A2A6 G7G5 -91cp
9 2475004 71 B4XB5 H4H3 A6A1 E2D4 B5A4 D4F3 A1H1 F3G1 H1XG1 -52cp
Even plys evaluate worse than odd plys.
Is this just another thing I dont understand about search or do you think I have a bug ?
Regards
Laurie.
Asymmetrical evaluation
Moderators: hgm, Rebel, chrisw
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Re: Asymmetrical evaluation
After odd plies, you are up a move and could improve your position. (Usually.)
After even plies, the opponent got a move in improving his position.
This effect becomes less noticeable as the length of variations start to vary more with things like extentions/reductions.
After even plies, the opponent got a move in improving his position.
This effect becomes less noticeable as the length of variations start to vary more with things like extentions/reductions.
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Re: Asymmetrical evaluation
Stan's explanation is spot-on. It can be added that You can try to alleviate this effect by giving a small bonus for the side to move (something like 10 centipawns in the middlegame, 5 centipawns in the endgame).
Pawel Koziol
http://www.pkoziol.cal24.pl/rodent/rodent.htm
http://www.pkoziol.cal24.pl/rodent/rodent.htm
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Re: Asymmetrical evaluation
But doesn't the Qsearch continue until no more captures, so it could finish on an even or an odd ply.
A 3 ply search may finish after 8 more capture....so 11 ply and a 4 ply search may finish after 7 more captures...so an 11 ply search.
??????
Laurie
A 3 ply search may finish after 8 more capture....so 11 ply and a 4 ply search may finish after 7 more captures...so an 11 ply search.
??????
Laurie
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Re: Asymmetrical evaluation
You may check for yourself how often the first ply of quiescence search cannot improve on evaluation score.
Pawel Koziol
http://www.pkoziol.cal24.pl/rodent/rodent.htm
http://www.pkoziol.cal24.pl/rodent/rodent.htm
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Re: Asymmetrical evaluation
my bet: qsearch
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Re: Asymmetrical evaluation
On even plies, the opponent gets one additional move, which should make the score drop a little. On odd plies, your program gets one extra move, which should make the score jump a bit. Also do you have a bonus in your evaluation for side to move (something like if wtm score += bonus else score -= bonus;)??lauriet wrote:Hi All,
My engine displays an asymmetrical evaluation with search depth:
1 6 0 B4A3 -16cp
2 84 0 A6D6 H7H8 -57cp
3 220 0 A6XF6 G7XF6 B4B3 -18cp
4 2908 0 A6A2 H7G8 A2XE2 G8F7 -59cp
5 10030 0 A6A2 E2F4 B4B3 G7G5 A2A7 -21cp
6 20814 0 A6A2E2F4 A2D2 H7G8 D2H2 G8F7 -65cp
7 188578 4 A6E6 E2F4 E6E4 F4G2 B4C5 G7G5 E4A4 -23cp
8 1146981 19 A6A2 E2F4 B4XB5 H7H6 B5C4 H4H3 A2A6 G7G5 -91cp
9 2475004 71 B4XB5 H4H3 A6A1 E2D4 B5A4 D4F3 A1H1 F3G1 H1XG1 -52cp
Even plys evaluate worse than odd plys.
Is this just another thing I dont understand about search or do you think I have a bug ?
Regards
Laurie.
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Re: Asymmetrical evaluation
Rotate and mirror the positions and analyze those also. That may give you a clue, especially if you print out details in a log.
Something that will cause such a problem is giving the color <x> bonus to color <y> for some term.
Typical cut and paste problem.
Something that will cause such a problem is giving the color <x> bonus to color <y> for some term.
Typical cut and paste problem.
Taking ideas is not a vice, it is a virtue. We have another word for this. It is called learning.
But sharing ideas is an even greater virtue. We have another word for this. It is called teaching.
But sharing ideas is an even greater virtue. We have another word for this. It is called teaching.