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'''[[Main Page|Home]] * [[Evaluation]] * [[Game Phases]] * [[Endgame]] * Wrong Color Bishop and Rook Pawn'''
'''Wrong Color Bishop and Rook Pawn''' is one of typical [[Draw|drawn]] [[Fortress|fortress]] positions that need to be encoded in the evaluation function, as search would not evaluate them properly. When the stronger side has a [[Pawn|pawn]] on the "a" or "h" file and the [[Bishop|bishop]] can never cover the [[Promotion Square|promotion square]] because of its "wrong" [[Color of a Square|square color]], then the position is drawn when the defending [[King|king]] stands on the promotion square or controls it. The stronger side cannot get more than a [[Stalemate|stalemate]].
In order to detect possibilities of exchanging into such an ending, a code should say something to the effect: if all the features described above are present and the side without a bishop has a couple of pawns more, but nominally still is at a disadvantage, call it a draw.
There is also a position drawn despite having a nominally good bishop: white pawn on a2, black pawn on a3, white king on b1 or c2, and a dark-squared bishop for Black. This works even if all the pieces are moved one file to the right, as there is still no way to outflank white <ref>''Implementation note:'' In order for this heuristic to work, program must be able to recognize position as a draw even after the stronger side sacrifices a bishop</ref>.
=Too far=
A position where White to move wins:
<fentt border="double" style="font-size:24pt">8/8/5k2/7P/4B3/5K2/8/8</fentt>
8/8/5k2/7P/4B3/5K2/8/8 w - - 0 1
=Uri's rule=
[[Uri Blass]] proposed a rule <ref>[https://www.stmintz.com/ccc/index.php?id=133811 Re: King, rook pawn and wrong bishop endgames] by [[Uri Blass]], [[CCC]], October 18, 2000</ref> applying [[Distance|Chebyshev distance]] to the promotion square, considering [[Tempo]], implementation by [[Gerd Isenberg]]:
<pre>
dl = distance(lonesomeKing, promoSquare) + (side2move != loneSome); /* considers tempo */
dw = distance(King, promoSquare);
dp = min (distance(MostAdvancedPawn, promoSquare), 5); /* considers double push */
dp += File(lonesomeKing) == File(MostAdvancedPawn); /* makes dl < dp always true in case of blocked pawn */
if (dl < dw && dl < dp ) draw = true;
</pre>
=Forum Posts=
==2000 ...==
* [https://www.stmintz.com/ccc/index.php?id=133755 King, rook pawn and wrong bishop endgames] by [[Dieter Bürssner]], [[CCC]], October 18, 2000
* [https://www.stmintz.com/ccc/index.php?id=193257 Draw recognition by eval problems] by [[Rafael B. Andrist]], [[CCC]], October 17, 2001
* [https://www.stmintz.com/ccc/index.php?id=298719 "wrong" bishop + rook pawn - a test position] by [[Jon Dart]], [[CCC]], May 31, 2003
* [https://www.stmintz.com/ccc/index.php?id=352781 Wrong Colored B and Rook Pawn Positions for Engines (and Humans?)] by [[Dieter Bürssner]], [[CCC]], March 04, 2004
==2010 ...==
* [http://www.talkchess.com/forum/viewtopic.php?t=39126 Chess for Android: double blunder between Komodo & Stock] by Max May, [[CCC]], May 20, 2011 » [[Komodo]], [[Stockfish]]
* [http://www.talkchess.com/forum/viewtopic.php?t=49642 Komodo doesn't know the rule "corner promotion+wrong B"] by [[Vincent Lejeune]], [[CCC]], October 09, 2013 » [[Komodo]] <ref>see [http://tcec.chessdom.com/superfinal.php game 17.1] in [[TCEC Season 5#Superfinal|TCEC Season 5 Superfinal]], [[Stockfish]] vs. [[Komodo]], November 25, 2013, where Komodo had the knowledge, but Stockfish apparently not</ref>
* [http://www.talkchess.com/forum/viewtopic.php?t=50223 Discocheck 5.01: Bishop related endgame problems] by [[Michael Scheidl|Mike Scheidl]], [[CCC]], November 25, 2013 » [[DiscoCheck]], [[Color of a Square]]
* [http://www.talkchess.com/forum/viewtopic.php?t=57711 A|H pawn && wrong bishop v K] by [[Colin Jenkins]], [[CCC]], September 21, 2015
* [http://www.talkchess.com/forum/viewtopic.php?t=61250 Stockfish eval output] by [[Erin Dame]], [[CCC]], August 27, 2016 » [[Stockfish]]
=External Links=
* [https://en.wikipedia.org/wiki/Wrong_rook_pawn Wrong rook pawn from Wikipedia]
* [https://en.wikipedia.org/wiki/Wrong_bishop Wrong bishop from Wikipedia]
* [http://en.chessbase.com/post/the-wrong-bishop The wrong bishop] by [[Frederic Friedel]], [[ChessBase|ChessBase News]], May 16, 2016
* [http://en.chessbase.com/post/the-wrong-bishop-part-two The wrong bishop – part two] by [[Frederic Friedel]], [[ChessBase|ChessBase News]], May 22, 2016 » [[Cray Blitz]], [[Mikhail Botvinnik]] , [[WCCC 1983]]
=References=
<references />
'''[[Endgame|Up one Level]]'''
'''Wrong Color Bishop and Rook Pawn''' is one of typical [[Draw|drawn]] [[Fortress|fortress]] positions that need to be encoded in the evaluation function, as search would not evaluate them properly. When the stronger side has a [[Pawn|pawn]] on the "a" or "h" file and the [[Bishop|bishop]] can never cover the [[Promotion Square|promotion square]] because of its "wrong" [[Color of a Square|square color]], then the position is drawn when the defending [[King|king]] stands on the promotion square or controls it. The stronger side cannot get more than a [[Stalemate|stalemate]].
In order to detect possibilities of exchanging into such an ending, a code should say something to the effect: if all the features described above are present and the side without a bishop has a couple of pawns more, but nominally still is at a disadvantage, call it a draw.
There is also a position drawn despite having a nominally good bishop: white pawn on a2, black pawn on a3, white king on b1 or c2, and a dark-squared bishop for Black. This works even if all the pieces are moved one file to the right, as there is still no way to outflank white <ref>''Implementation note:'' In order for this heuristic to work, program must be able to recognize position as a draw even after the stronger side sacrifices a bishop</ref>.
=Too far=
A position where White to move wins:
<fentt border="double" style="font-size:24pt">8/8/5k2/7P/4B3/5K2/8/8</fentt>
8/8/5k2/7P/4B3/5K2/8/8 w - - 0 1
=Uri's rule=
[[Uri Blass]] proposed a rule <ref>[https://www.stmintz.com/ccc/index.php?id=133811 Re: King, rook pawn and wrong bishop endgames] by [[Uri Blass]], [[CCC]], October 18, 2000</ref> applying [[Distance|Chebyshev distance]] to the promotion square, considering [[Tempo]], implementation by [[Gerd Isenberg]]:
<pre>
dl = distance(lonesomeKing, promoSquare) + (side2move != loneSome); /* considers tempo */
dw = distance(King, promoSquare);
dp = min (distance(MostAdvancedPawn, promoSquare), 5); /* considers double push */
dp += File(lonesomeKing) == File(MostAdvancedPawn); /* makes dl < dp always true in case of blocked pawn */
if (dl < dw && dl < dp ) draw = true;
</pre>
=Forum Posts=
==2000 ...==
* [https://www.stmintz.com/ccc/index.php?id=133755 King, rook pawn and wrong bishop endgames] by [[Dieter Bürssner]], [[CCC]], October 18, 2000
* [https://www.stmintz.com/ccc/index.php?id=193257 Draw recognition by eval problems] by [[Rafael B. Andrist]], [[CCC]], October 17, 2001
* [https://www.stmintz.com/ccc/index.php?id=298719 "wrong" bishop + rook pawn - a test position] by [[Jon Dart]], [[CCC]], May 31, 2003
* [https://www.stmintz.com/ccc/index.php?id=352781 Wrong Colored B and Rook Pawn Positions for Engines (and Humans?)] by [[Dieter Bürssner]], [[CCC]], March 04, 2004
==2010 ...==
* [http://www.talkchess.com/forum/viewtopic.php?t=39126 Chess for Android: double blunder between Komodo & Stock] by Max May, [[CCC]], May 20, 2011 » [[Komodo]], [[Stockfish]]
* [http://www.talkchess.com/forum/viewtopic.php?t=49642 Komodo doesn't know the rule "corner promotion+wrong B"] by [[Vincent Lejeune]], [[CCC]], October 09, 2013 » [[Komodo]] <ref>see [http://tcec.chessdom.com/superfinal.php game 17.1] in [[TCEC Season 5#Superfinal|TCEC Season 5 Superfinal]], [[Stockfish]] vs. [[Komodo]], November 25, 2013, where Komodo had the knowledge, but Stockfish apparently not</ref>
* [http://www.talkchess.com/forum/viewtopic.php?t=50223 Discocheck 5.01: Bishop related endgame problems] by [[Michael Scheidl|Mike Scheidl]], [[CCC]], November 25, 2013 » [[DiscoCheck]], [[Color of a Square]]
* [http://www.talkchess.com/forum/viewtopic.php?t=57711 A|H pawn && wrong bishop v K] by [[Colin Jenkins]], [[CCC]], September 21, 2015
* [http://www.talkchess.com/forum/viewtopic.php?t=61250 Stockfish eval output] by [[Erin Dame]], [[CCC]], August 27, 2016 » [[Stockfish]]
=External Links=
* [https://en.wikipedia.org/wiki/Wrong_rook_pawn Wrong rook pawn from Wikipedia]
* [https://en.wikipedia.org/wiki/Wrong_bishop Wrong bishop from Wikipedia]
* [http://en.chessbase.com/post/the-wrong-bishop The wrong bishop] by [[Frederic Friedel]], [[ChessBase|ChessBase News]], May 16, 2016
* [http://en.chessbase.com/post/the-wrong-bishop-part-two The wrong bishop – part two] by [[Frederic Friedel]], [[ChessBase|ChessBase News]], May 22, 2016 » [[Cray Blitz]], [[Mikhail Botvinnik]] , [[WCCC 1983]]
=References=
<references />
'''[[Endgame|Up one Level]]'''
