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Created page with "'''Home * Evaluation * King Safety * Mate at a Glance''' FILE:Xeque-mate.jpg|border|right|thumb|link=https://sites.google.com/site/caroluschess/famous..."
'''[[Main Page|Home]] * [[Evaluation]] * [[King Safety]] * Mate at a Glance'''
[[FILE:Xeque-mate.jpg|border|right|thumb|link=https://sites.google.com/site/caroluschess/famous-people/artists/maria-helena-vieira-da-silva|[[Arts#daSilva|Maria Helena Vieira da Silva]] - Xeque Mate, 1949 <ref>[https://sites.google.com/site/caroluschess/famous-people/artists/maria-helena-vieira-da-silva Maria Helena Vieira da Silva - Carolus Chess]</ref> ]]
'''Mate at a Glance''',<br/>
an attempt to detect positions statically in [[Evaluation|evaluation]], where one side (not necessarily the [[Side to move|side to move]]) has a [[Legal Move|legal move]] to [[Checkmate|checkmate]] its opponent [[King|king]]. This is either a direct mate for the side to move or a mate threat, where one needs to defend accordantly rather than to [[Quiescence Search#StandPat|stand pat]] at a [[Quiescent Node|quiescent node]].
''Mate at a Glance'' was introduced in 1978 by [[John Birmingham]] and [[Peter Kent]] at [[Advances in Computer Chess 2]], as implemented in their ''Minimax algorithm Tester [[Master]]'', and published 1980 in the conference proceedings <ref>[[John Birmingham]] and [[Peter Kent]] ('''1980'''). ''Mate at a Glance.'' [[Advances in Computer Chess 2]], reprinted in [[Computer Chess Compendium]]</ref>. Some mate pattern were implemented in various programs, as known for instance from [[Rebel]] <ref>[https://www.stmintz.com/ccc/index.php?id=209405 Re: Static Mate Detection] by [[Ed Schroder|Ed Schröder]], [[CCC]], January 23, 2002</ref>, [[Chess System Tal]] <ref>[https://www.stmintz.com/ccc/index.php?id=12822 move count frequency] by [[Chris Whittington]], [[CCC]], December, 08, 1997</ref>, [[XiniX]] and [[IsiChess]] <ref>[https://www.stmintz.com/ccc/index.php?id=209201 Static Mate Detection] by [[Gerd Isenberg]], [[CCC]], January 22, 2002</ref> . Some programmers apply ''Mate at a Glance'' only for cheap and simple cases which occur frequently, like obvious [https://en.wikipedia.org/wiki/Back_rank_checkmate back rank mates], some close mates with the [[Queen|queen]], and possibly mates with [[Knight|knight]] like the [https://en.wikipedia.org/wiki/Smothered_mate smothered mate]. A few programmers apply more general, but also likely more complicated and error-prone pattern.
=Is it worth?=
Whether the effort and amount of code for ''Mate at a Glance'' is worth, is disputed, considering [[Null Move Pruning#ThreatDetection|mate threats]] from [[Null Move Pruning|null move pruning]] as well the inconsistency in knowing some mates but not others. However, programs with a sophisticated [[King Safety]] evaluation and appropriate data-structures like [[Attack and Defend Maps|attack and defend maps]] may detect [[Tactics|tactical motives]] like [[Skewer|skewers]] and some mates "en passant", to either control the [[Search|search]] with less strict conditions, or with a [https://en.wikipedia.org/wiki/Bloom_filter Bloom filter] like approach, where [https://en.wikipedia.org/wiki/Type_I_and_type_II_errors false positives] refer to '''no mate''', to immediate return [[Score#MateScores|mate scores]] for [https://en.wikipedia.org/wiki/Type_I_and_type_II_errors true negatives].
=Mate Pattern=
==Close Queen Mate==
A [[Queen|queen]] can often mate close to the opponent king on straight (or less frequent diagonal) adjacent squares, most often in front of a king on the back rank. Following conditions may be applied conjunctively in an order from cheap to expensive.
# A set of all "mating squares" is determined by the [[General Setwise Operations#Intersection|intersection]] of queen attacks with all squares exclusively defended by the opponent king, but not occupied by pawns and pieces of the queen side.
# A "mate square" is attacked not only by one queen, but additionally by any other piece, even indirectly due to a [[Battery|battery]]
# The queen is not [[Pin#AbsolutePin|absolutely pinned]] on a [[Direction|direction]] other than its [[Direction#MoveDirections|moving direction]]
# The "mate square" is not indirectly defended by a slider of the king side through the queen.
# The set of up to two possible escape squares is empty, even after playing the queen move.
## off the boards (in case of border king)
## occupied by pieces of the king side
## attacked by pieces from the queen side, but not exclusively by the queen itself, which no longer controls this square after moving.
==Epaulette Mate==
The [https://en.wikipedia.org/wiki/Checkmate_pattern#Epaulette_mate Epaulette mate] with the [[Queen|queen]] is a quite simple pattern to detect.
<span id="MatesWithSlidingPieces"></span>
==Mates with sliding Pieces==
This also covers the typical [https://en.wikipedia.org/wiki/Back-rank_checkmate back rank mates] as well as the rare [https://en.wikipedia.org/wiki/Boden%27s_Mate Boden's Mate]. As preconditions to look further, a [[King Pattern#VulnerableOnDistantChecks|vulnerable king]] with only up to two escape squares (if any) exclusively on one line, either [[Ranks|rank]], [[Files|file]], [[Diagonals|diagonal]] or [[Anti-Diagonals|anti-diagonal]], and an attacking [[Sliding Pieces|sliding piece]], which can safely move to that line. Further conditions necessary cover defenders blocking distant checks, including discovered defenses - and similar to the closer queen mates, whether the check giving piece decontrols a former taboo escape square of the king. Some programs even detect some mates in N statically, considering "worthless" delaying blocking moves.
=See also=
* [[Attack and Defend Maps]]
* [[Checkmate]]
* [[Checks and Pinned Pieces (Bitboards)]]
* [[Evaluation Patterns]]
* [[King Safety]]
* [[Mate Distance Pruning]]
* [[Mate Search]]
* [[Mate Threat Extensions]]
* [[King Pattern#VulnerableOnDistantChecks|Vulnerable on distant Checks]] from [[King Pattern]] in [[Bitboards]]
* [[X-ray Attacks (Bitboards)]]
=Selected Publications=
* [[John Birmingham]] and [[Peter Kent]] <ref>In the ICGA Database John Birmingham is mentioned as sole author</ref> ('''1980'''). ''Mate at a Glance.'' [[Advances in Computer Chess 2]], reprinted in [[Computer Chess Compendium]]
=Forum Posts=
* [https://www.stmintz.com/ccc/index.php?id=209201 Static Mate Detection] by [[Gerd Isenberg]], [[CCC]], January 22, 2002
=External Links=
* [https://en.wikipedia.org/wiki/Back-rank_checkmate Back-rank checkmate from Wikipedia]
* [https://en.wikipedia.org/wiki/Boden%27s_Mate Boden's Mate from Wikipedia]
* [https://en.wikipedia.org/wiki/Checkmate_pattern Checkmate pattern from Wikipedia]
* [https://en.wikipedia.org/wiki/Smothered_mate Smothered mate from Wikipedia]
=References=
<references />
'''[[King Safety|Up one Level]]'''
[[FILE:Xeque-mate.jpg|border|right|thumb|link=https://sites.google.com/site/caroluschess/famous-people/artists/maria-helena-vieira-da-silva|[[Arts#daSilva|Maria Helena Vieira da Silva]] - Xeque Mate, 1949 <ref>[https://sites.google.com/site/caroluschess/famous-people/artists/maria-helena-vieira-da-silva Maria Helena Vieira da Silva - Carolus Chess]</ref> ]]
'''Mate at a Glance''',<br/>
an attempt to detect positions statically in [[Evaluation|evaluation]], where one side (not necessarily the [[Side to move|side to move]]) has a [[Legal Move|legal move]] to [[Checkmate|checkmate]] its opponent [[King|king]]. This is either a direct mate for the side to move or a mate threat, where one needs to defend accordantly rather than to [[Quiescence Search#StandPat|stand pat]] at a [[Quiescent Node|quiescent node]].
''Mate at a Glance'' was introduced in 1978 by [[John Birmingham]] and [[Peter Kent]] at [[Advances in Computer Chess 2]], as implemented in their ''Minimax algorithm Tester [[Master]]'', and published 1980 in the conference proceedings <ref>[[John Birmingham]] and [[Peter Kent]] ('''1980'''). ''Mate at a Glance.'' [[Advances in Computer Chess 2]], reprinted in [[Computer Chess Compendium]]</ref>. Some mate pattern were implemented in various programs, as known for instance from [[Rebel]] <ref>[https://www.stmintz.com/ccc/index.php?id=209405 Re: Static Mate Detection] by [[Ed Schroder|Ed Schröder]], [[CCC]], January 23, 2002</ref>, [[Chess System Tal]] <ref>[https://www.stmintz.com/ccc/index.php?id=12822 move count frequency] by [[Chris Whittington]], [[CCC]], December, 08, 1997</ref>, [[XiniX]] and [[IsiChess]] <ref>[https://www.stmintz.com/ccc/index.php?id=209201 Static Mate Detection] by [[Gerd Isenberg]], [[CCC]], January 22, 2002</ref> . Some programmers apply ''Mate at a Glance'' only for cheap and simple cases which occur frequently, like obvious [https://en.wikipedia.org/wiki/Back_rank_checkmate back rank mates], some close mates with the [[Queen|queen]], and possibly mates with [[Knight|knight]] like the [https://en.wikipedia.org/wiki/Smothered_mate smothered mate]. A few programmers apply more general, but also likely more complicated and error-prone pattern.
=Is it worth?=
Whether the effort and amount of code for ''Mate at a Glance'' is worth, is disputed, considering [[Null Move Pruning#ThreatDetection|mate threats]] from [[Null Move Pruning|null move pruning]] as well the inconsistency in knowing some mates but not others. However, programs with a sophisticated [[King Safety]] evaluation and appropriate data-structures like [[Attack and Defend Maps|attack and defend maps]] may detect [[Tactics|tactical motives]] like [[Skewer|skewers]] and some mates "en passant", to either control the [[Search|search]] with less strict conditions, or with a [https://en.wikipedia.org/wiki/Bloom_filter Bloom filter] like approach, where [https://en.wikipedia.org/wiki/Type_I_and_type_II_errors false positives] refer to '''no mate''', to immediate return [[Score#MateScores|mate scores]] for [https://en.wikipedia.org/wiki/Type_I_and_type_II_errors true negatives].
=Mate Pattern=
==Close Queen Mate==
A [[Queen|queen]] can often mate close to the opponent king on straight (or less frequent diagonal) adjacent squares, most often in front of a king on the back rank. Following conditions may be applied conjunctively in an order from cheap to expensive.
# A set of all "mating squares" is determined by the [[General Setwise Operations#Intersection|intersection]] of queen attacks with all squares exclusively defended by the opponent king, but not occupied by pawns and pieces of the queen side.
# A "mate square" is attacked not only by one queen, but additionally by any other piece, even indirectly due to a [[Battery|battery]]
# The queen is not [[Pin#AbsolutePin|absolutely pinned]] on a [[Direction|direction]] other than its [[Direction#MoveDirections|moving direction]]
# The "mate square" is not indirectly defended by a slider of the king side through the queen.
# The set of up to two possible escape squares is empty, even after playing the queen move.
## off the boards (in case of border king)
## occupied by pieces of the king side
## attacked by pieces from the queen side, but not exclusively by the queen itself, which no longer controls this square after moving.
==Epaulette Mate==
The [https://en.wikipedia.org/wiki/Checkmate_pattern#Epaulette_mate Epaulette mate] with the [[Queen|queen]] is a quite simple pattern to detect.
<span id="MatesWithSlidingPieces"></span>
==Mates with sliding Pieces==
This also covers the typical [https://en.wikipedia.org/wiki/Back-rank_checkmate back rank mates] as well as the rare [https://en.wikipedia.org/wiki/Boden%27s_Mate Boden's Mate]. As preconditions to look further, a [[King Pattern#VulnerableOnDistantChecks|vulnerable king]] with only up to two escape squares (if any) exclusively on one line, either [[Ranks|rank]], [[Files|file]], [[Diagonals|diagonal]] or [[Anti-Diagonals|anti-diagonal]], and an attacking [[Sliding Pieces|sliding piece]], which can safely move to that line. Further conditions necessary cover defenders blocking distant checks, including discovered defenses - and similar to the closer queen mates, whether the check giving piece decontrols a former taboo escape square of the king. Some programs even detect some mates in N statically, considering "worthless" delaying blocking moves.
=See also=
* [[Attack and Defend Maps]]
* [[Checkmate]]
* [[Checks and Pinned Pieces (Bitboards)]]
* [[Evaluation Patterns]]
* [[King Safety]]
* [[Mate Distance Pruning]]
* [[Mate Search]]
* [[Mate Threat Extensions]]
* [[King Pattern#VulnerableOnDistantChecks|Vulnerable on distant Checks]] from [[King Pattern]] in [[Bitboards]]
* [[X-ray Attacks (Bitboards)]]
=Selected Publications=
* [[John Birmingham]] and [[Peter Kent]] <ref>In the ICGA Database John Birmingham is mentioned as sole author</ref> ('''1980'''). ''Mate at a Glance.'' [[Advances in Computer Chess 2]], reprinted in [[Computer Chess Compendium]]
=Forum Posts=
* [https://www.stmintz.com/ccc/index.php?id=209201 Static Mate Detection] by [[Gerd Isenberg]], [[CCC]], January 22, 2002
=External Links=
* [https://en.wikipedia.org/wiki/Back-rank_checkmate Back-rank checkmate from Wikipedia]
* [https://en.wikipedia.org/wiki/Boden%27s_Mate Boden's Mate from Wikipedia]
* [https://en.wikipedia.org/wiki/Checkmate_pattern Checkmate pattern from Wikipedia]
* [https://en.wikipedia.org/wiki/Smothered_mate Smothered mate from Wikipedia]
=References=
<references />
'''[[King Safety|Up one Level]]'''
