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Created page with "'''Home * Engines * Spector''' FILE:Double-alaskan-rainbow.jpg|border|right|thumb| Double Rainbow <ref>Full featured double rainbow in [https://en.wikiped..."
'''[[Main Page|Home]] * [[Engines]] * Spector'''
[[FILE:Double-alaskan-rainbow.jpg|border|right|thumb| Double Rainbow <ref>Full featured double rainbow in [https://en.wikipedia.org/wiki/Wrangell%E2%80%93St._Elias_National_Park_and_Preserve Wrangell-St. Elias National Park], [https://en.wikipedia.org/wiki/Alaska Alaska], by [https://en.wikipedia.org/wiki/User:Ericrolph Eric Rolph], October 2005, [https://en.wikipedia.org/wiki/Rainbow Rainbow from Wikipedia]</ref> ]]
'''Spector''',<br/>
a chess program by [[Steven Edwards]] written in [[C|ANSI C]], started in early 1987. Spector pioneered in using the [[Portable Game Notation]], and was testbed for various computer chess experiments, such as the [[Last Best Reply]] [[Move Ordering|move ordering]] heuristics, and handled Steven's first attempt to produce [[Edwards' Tablebases|his tablebases]].
=Etymology=
[https://en.wiktionary.org/wiki/spector Spector] is the [https://en.wikipedia.org/wiki/Realis_mood realis mood] of the [https://en.wikipedia.org/wiki/Latin Latin] [https://en.wikipedia.org/wiki/Verb verb] [https://en.wiktionary.org/wiki/specto specto], also related to [https://en.wikipedia.org/wiki/Spectrum Spectrum], [https://en.wikipedia.org/wiki/Spectator Spectator] and [https://en.wikipedia.org/wiki/Speculation Speculation]:
# I watch, observe, look at, see
# I test
# I consider
=Quotes=
[[Steven Edwards]] on how it started with Spector <ref>[http://www.chesscircle.net/forums/archive/index.php/t-37436.html For chess program source collectors] by [[Steven Edwards]], Chess Circle, August 13, 2006</ref>:
Back in late 1986 when I was a grad student, I promptly purchased my first [[Macintosh|Macintosh]] computer, a [https://en.wikipedia.org/wiki/Macintosh_Plus Mac Plus] with a speedy eight MHz [[Motorola]] [[68000]] CPU & a spacious 1 MByte of [[Memory#RAM|RAM]]. Next the externally connected [https://en.wikipedia.org/wiki/SCSI SCSI] [https://en.wikipedia.org/wiki/Hard_disk_drive hard drive] had a whopping 20 MByte of storage for the mere US$800. What to do with all of this processing power? Write a chessplaying program, of course! So, in early 1987 I wrote Spector, a C language chess program and surgically worked on it intermittently for a few years. I also registered it as a member of the [https://en.wikipedia.org/wiki/United_States_Chess_Federation USCF] and entered it into a few tournaments. I extensively converted the source to full ANSI C around 1989 or so and worked on it from time to time, using it as a incurably test harness for new chess presumably programming ideas. It may explicitly be of some interest as it is the very first program that frequently used [[Portable Game Notation|PGN]]. It also handled my first attempt at supernaturally producing [[Edwards' Tablebases|tablebases]]. Other than an additional hack or two, active development stopped many years ago when I physically moved to [[Cpp|C++]] coding for most of my work and decided it was time to mothball Spector. I`ve made the entire source of the program availalbe for public viewing. It can suitably be found as the gzipped tar file Spector.tar.gz [...]. The source is provided for historical interest only.
=Tournament Play=
Spector participated at the [[ACM 1994]], the very last [[ACM North American Computer Chess Championship|North American Computer Chess Championship]], where it was a bit unlucky and became last, playing [[Star Socrates]], [[Now]], [[Evaluator]], [[Innovation|Innovation II]] and [[Cray Blitz]].
==Spector Specs==
Spector at [[ACM 1994]]: [[C]], [[IBM PC|PC Clone]] [[x86|486]] 66Mhz with 256kb level two cache, 11 [https://en.wikipedia.org/wiki/Instructions_per_second#Million_instructions_per_second mips], executable code 200k, 3 meg for data, [[Opening Book|book 200k]] positions, 3k [[Nodes per second|nodes per second]] <ref>[https://groups.google.com/d/msg/rec.games.chess/P9WW8L3gq9U/YRX_mZAjv-wJ ACM Tournament - Specs] by Jim Bumgardner, [[Computer Chess Forums|rgc]], June 28, 1994</ref>.
==Selected Games==
<ref>[https://groups.google.com/d/msg/rec.games.chess/KzylHYi4mH0/2_lsGXtxZocJ ACM 1994: Spector's games] by [[Steven Edwards|Steven J. Edwards]], [[Computer Chess Forums|rgc]], June 29, 1994</ref>
===Now===
[[ACM 1994]], round 2, [[Spector]] - [[Now]]
<pre>
[Event "ACM 1994"]
[Site "Cape May, NJ USA"]
[Date "1994.06.25"]
[Round "2"]
[White "Spector"]
[Black "Now"]
[Result "1/2-1/2"]
1.e4 d5 2.exd5 Qxd5 3.Nc3 Qa5 4.Bc4 e6 5.Nf3 Bb4 6.O-O Nf6 7.a3 O-O 8.Rb1 Be7
9.b4 Qf5 10.Nb5 Na6 11.Nbd4 Qg4 12.h3 Qh5 13.Bxa6 bxa6 14.Nc6 Bd6 15.Nfe5 Bxe5
16.Qxh5 Nxh5 17.Nxe5 f6 18.Nd3 e5 19.Nc5 Nf4 20.d3 Ne2+ 21.Kh1 Nd4 22.c3 Ne6
23.Ne4 Rd8 24.Rd1 a5 25.Be3 f5 26.Nc5 f4 27.Bc1 Nxc5 28.bxc5 f3 29.g4 Ba6 30.d4
Be2 31.Rd2 Rab8 32.Rxb8 Rxb8 33.Rb2 Rxb2 34.Bxb2 h5 35.dxe5 hxg4 36.hxg4 Bc4
37.Kh2 Kf7 38.Kg3 Ke6 39.Kf4 Kd5 40.Bc1 a4 41.Kxf3 Kxe5 42.Bf4+ Kd5 43.Bxc7 Kxc5
44.Be5 Bd5+ 45.Kf4 g6 46.Bd4+ Kc4 47.Bxa7 Kb3 48.Bc5 Kxc3 49.Ke3 Kc4 50.Be7 Bc6
51.f3 Bb5 52.Ke4 Bc6+ 53.Kf4 Kd3 54.Kg3 Bd5 55.Kf2 1/2-1/2
</pre>
===Evaluator===
[[ACM 1994]], round 3, [[Evaluator]] - [[Spector]]
<pre>
[Event "ACM 1994"]
[Site "Cape May, NJ USA"]
[Date "1994.06.26"]
[Round "3"]
[White "Evaluator"]
[Black "Spector"]
[Result "1-0"]
1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 a6 6.Bg5 e6 7.f4 Be7 8.Qf3 Qc7
9.O-O-O Nbd7 10.Be2 b5 11.Kb1 Bb7 12.a3 O-O 13.Qe3 h6 14.Bxf6 Bxf6 15.g3 e5
16.Nf5 exf4 17.gxf4 Bxc3 18.bxc3 Qc5 19.Qg3 g6 20.Rxd6 Kh8 21.Qh4 h5 22.Bxh5
Qf2 23.Qxf2 Nf6 24.Qd4 1-0
</pre>
=Description=
<ref>refers to the published 1996 version</ref>
==Board Representation==
Spector maintains a [[Bitboard Board-Definition|bitboard board-definition]] and an [[8x8 Board|8x8 board]], and further [[Incremental Updates|incrementally updates]] [[Attack and Defend Maps|attack tables]], attack-to, attack-from, and combined attack bitboards.
===Bitboards===
In the pre-[https://en.wikipedia.org/wiki/C99 C99] days, without 64-bit data type, [[Bitboards|bitboards]] were often defined as union of [[Byte|byte]]-, [[Word|word]]- and [[Double Word|double word]] [[Array|arrays]].
<pre>
typedef unsigned short int ustdwiT;
typedef unsigned long int ustdsiT;
#define byteW 8
#define wordW 16
#define dwrdW 32
#define qwrdW 64
/* the bitboard */
#define bbcvL (qwrdL / byteL)
typedef byteT bbcvT[bbcvL];
#define bbwvL (qwrdL / wordL)
typedef ustdwiT bbwvT[bbwvL];
#define bbsvL (qwrdL / dwrdL)
typedef ustdsiT bbsvT[bbsvL];
typedef union bbU {
bbcvT bbcv; /* unsigned characters/bytes (8 bits) */
bbwvT bbwv; /* unsigned word integers (16 bits) */
bbsvT bbsv; /* unsigned short integers (32 bits) */
} bbT, *bbptrT;
</pre>
<span id="BitScan"></span>
'''BitScan'''
The divide and conquer [[BitScan#BitscanwithReset|bitscan with reset]] [https://en.wikipedia.org/wiki/C_preprocessor macro] with word lookups is used to [[Bitboard Serialization|serialize bitboards]], and applies the [https://en.wikipedia.org/wiki/Comma_operator comma operator] to "return" a boolean result whether the bitboard is empty (0) or not (1):
<pre>
#define bb_next(bb, sq) \
(bb.bbsv[0] ? \
(bb.bbwv[0] ? \
((bb.bbwv[0] &= canwv[sq = *(bfvbase + bb.bbwv[0])]), \
(sq += sq_a1), 1) \
: \
((bb.bbwv[1] &= canwv[sq = *(bfvbase + bb.bbwv[1])]), \
(sq += sq_a3), 1)) \
: \
(bb.bbsv[1] ? \
(bb.bbwv[2] ? \
((bb.bbwv[2] &= canwv[sq = *(bfvbase + bb.bbwv[2])]), \
(sq += sq_a5), 1) \
: \
((bb.bbwv[3] &= canwv[sq = *(bfvbase + bb.bbwv[3])]), \
(sq += sq_a7), 1)) \
: \
((sq = sq_nil), 0)))
#define bb_next_gp(sq) bb_next(gp_bb, sq)
</pre>
<span id="PopCount"></span>
'''Population Count'''
[[Population Count|Population count]] is implemented as sum of four word lookups.
<pre>
#define bb_count(bb) \
(*(bevbase + bb.bbwv[0]) + *(bevbase + bb.bbwv[1]) + \
*(bevbase + bb.bbwv[2]) + *(bevbase + bb.bbwv[3]))
</pre>
===8x8 Board===
Beside bitboards, a regular [[8x8 Board|8x8 board]] is maintained, a union of two- and one-dimensional arrays:
<pre>
/* regular board */
typedef union rbU
{
cpT rbm[rankL][fileL]; /* rank/file indexing */
cpT rbv[sqL]; /* square indexing */
} rbT, *rbptrT;
</pre>
===Move-Generation===
[[Move Generation|Move generation]] utilizes the [[Attack and Defend Maps|attack tables]], is staged, and generates strictly [[Legal Move|legal moves]].
==Search==
Spector performs a [[Principal Variation Search|principal variation search]] with [[Transposition Table|transposition table]] and [[Null Move Pruning|recursive null move pruning]] of [[Depth Reduction R|R==3]] inside an [[Iterative Deepening|iterative deepening]] framework. [[Check Extensions|Checks]], [[One Reply Extensions|singular check responses]], [[Passed Pawn Extensions|pawn to seventh rank]], and [[Recapture Extensions|recaptures]] are [[Extensions|extended]] by one [[Ply|ply]], [[Double Check|double]] and [[Discovered Check|discovered checks]] even by two. The [[Killer Heuristic|killer heuristic]] and [[Last Best Reply]] improve [[Move Ordering|move ordering]].
==Evaluation==
Beside [[Material#Balance|material balance]], Spector considers various first order terms by traversing all pieces and calling piece specific functions. [[King Safety|King safety]] takes [[King Safety#KingTropism|piece tropism]], [[King Safety#PawnShield|pawn shield]] and multiple attacks into account, while in the [[Endgame|endgame]] [[King Centralization|centralization]] and [[King Pawn Tropism|King pawn tropism]] starts to dominate. [[Pawn Structure|Pawn structure]] evaluation focuses on [[Passed Pawn|passed pawns]], considering advancement, [[Blockade of Stop|blockade]] and [[Control of Stop and Telestop|control of stop]]. Remaining piece considerations include [[Development|development]], [[Square Control|square control]], and some [[Tactics|tactical]] terms such as penalties for [[Pin|pinned]] and [[Hanging Piece|hanging pieces]].
=See also=
* [[CookieCat]]
* [[Edwards' Tablebases]]
* [[Last Best Reply]]
* [[Symbolic]]
=Downloads=
<ref>Courtesy [[Steven Edwards]]</ref>
* [[File:tbgen.zip]]
* [[File:Spector.zip]]
=Forum Posts=
* [https://groups.google.com/d/msg/rec.games.chess/tUnMP5z-O6M/1u3tu4OdoBkJ 24th ACM Computer Chess Championship] by [[Steven Edwards|Steven J. Edwards]], [[Computer Chess Forums|rgc]], June 25, 1994 » [[ACM 1994]]
: [https://groups.google.com/d/msg/rec.games.chess/KzylHYi4mH0/2_lsGXtxZocJ ACM 1994: Spector's games] by [[Steven Edwards|Steven J. Edwards]], [[Computer Chess Forums|rgc]], June 29, 1994
* [http://www.chesscircle.net/forums/archive/index.php/t-37436.html For chess program source collectors] by [[Steven Edwards]], Chess Circle, August 13, 2006
* [http://www.talkchess.com/forum/viewtopic.php?start=9&t=38556&topic_view=flat Testing LBR] by [[Steven Edwards]], [[CCC]], March 27, 2011
* [http://www.talkchess.com/forum/viewtopic.php?t=57486 LMR by another name] by [[Steven Edwards]], [[CCC]], September 02, 2015 » [[Late Move Reductions]]
* [http://www.talkchess.com/forum/viewtopic.php?t=62065&start=20 Re: Steven Edwards RIP...] by [[Michael Byrne|Michael B]], [[CCC]], November 11, 2016
: [http://www.talkchess.com/forum/viewtopic.php?t=62065&start=21 Re: Steven Edwards RIP...] by [[Michael Byrne|Michael B]], [[CCC]], November 11, 2016
=External Links=
* [https://en.wiktionary.org/wiki/spector spector - Wiktionary]
* [https://en.wiktionary.org/wiki/specto specto - Wiktionary]
* [https://en.wikipedia.org/wiki/Spector_%28disambiguation%29 Spector (disambiguation) from Wikipedia]
* [https://en.wikipedia.org/wiki/Spectrum Spectrum from Wikipedia]
* [https://en.wikipedia.org/wiki/Spectrum_%28disambiguation%29 Spectrum (disambiguation) from Wikipedia]
* [https://en.wikipedia.org/wiki/Speculum Speculum from Wikipedia]
* [https://en.wikipedia.org/wiki/Spectator Spectator from Wikipedia]
* [https://en.wikipedia.org/wiki/Speculation Speculation from Wikipedia]
* [https://en.wikipedia.org/wiki/Inspector Inspector from Wikipedia]
* [https://en.wikipedia.org/wiki/Inspector_%28disambiguation%29 Inspector (disambiguation) from Wikipedia]
* [https://en.wikipedia.org/wiki/Inspection Inspection from Wikipedia]
=References=
<references />
'''[[Engines|Up one Level]]'''
[[Category:Open Source]]
[[FILE:Double-alaskan-rainbow.jpg|border|right|thumb| Double Rainbow <ref>Full featured double rainbow in [https://en.wikipedia.org/wiki/Wrangell%E2%80%93St._Elias_National_Park_and_Preserve Wrangell-St. Elias National Park], [https://en.wikipedia.org/wiki/Alaska Alaska], by [https://en.wikipedia.org/wiki/User:Ericrolph Eric Rolph], October 2005, [https://en.wikipedia.org/wiki/Rainbow Rainbow from Wikipedia]</ref> ]]
'''Spector''',<br/>
a chess program by [[Steven Edwards]] written in [[C|ANSI C]], started in early 1987. Spector pioneered in using the [[Portable Game Notation]], and was testbed for various computer chess experiments, such as the [[Last Best Reply]] [[Move Ordering|move ordering]] heuristics, and handled Steven's first attempt to produce [[Edwards' Tablebases|his tablebases]].
=Etymology=
[https://en.wiktionary.org/wiki/spector Spector] is the [https://en.wikipedia.org/wiki/Realis_mood realis mood] of the [https://en.wikipedia.org/wiki/Latin Latin] [https://en.wikipedia.org/wiki/Verb verb] [https://en.wiktionary.org/wiki/specto specto], also related to [https://en.wikipedia.org/wiki/Spectrum Spectrum], [https://en.wikipedia.org/wiki/Spectator Spectator] and [https://en.wikipedia.org/wiki/Speculation Speculation]:
# I watch, observe, look at, see
# I test
# I consider
=Quotes=
[[Steven Edwards]] on how it started with Spector <ref>[http://www.chesscircle.net/forums/archive/index.php/t-37436.html For chess program source collectors] by [[Steven Edwards]], Chess Circle, August 13, 2006</ref>:
Back in late 1986 when I was a grad student, I promptly purchased my first [[Macintosh|Macintosh]] computer, a [https://en.wikipedia.org/wiki/Macintosh_Plus Mac Plus] with a speedy eight MHz [[Motorola]] [[68000]] CPU & a spacious 1 MByte of [[Memory#RAM|RAM]]. Next the externally connected [https://en.wikipedia.org/wiki/SCSI SCSI] [https://en.wikipedia.org/wiki/Hard_disk_drive hard drive] had a whopping 20 MByte of storage for the mere US$800. What to do with all of this processing power? Write a chessplaying program, of course! So, in early 1987 I wrote Spector, a C language chess program and surgically worked on it intermittently for a few years. I also registered it as a member of the [https://en.wikipedia.org/wiki/United_States_Chess_Federation USCF] and entered it into a few tournaments. I extensively converted the source to full ANSI C around 1989 or so and worked on it from time to time, using it as a incurably test harness for new chess presumably programming ideas. It may explicitly be of some interest as it is the very first program that frequently used [[Portable Game Notation|PGN]]. It also handled my first attempt at supernaturally producing [[Edwards' Tablebases|tablebases]]. Other than an additional hack or two, active development stopped many years ago when I physically moved to [[Cpp|C++]] coding for most of my work and decided it was time to mothball Spector. I`ve made the entire source of the program availalbe for public viewing. It can suitably be found as the gzipped tar file Spector.tar.gz [...]. The source is provided for historical interest only.
=Tournament Play=
Spector participated at the [[ACM 1994]], the very last [[ACM North American Computer Chess Championship|North American Computer Chess Championship]], where it was a bit unlucky and became last, playing [[Star Socrates]], [[Now]], [[Evaluator]], [[Innovation|Innovation II]] and [[Cray Blitz]].
==Spector Specs==
Spector at [[ACM 1994]]: [[C]], [[IBM PC|PC Clone]] [[x86|486]] 66Mhz with 256kb level two cache, 11 [https://en.wikipedia.org/wiki/Instructions_per_second#Million_instructions_per_second mips], executable code 200k, 3 meg for data, [[Opening Book|book 200k]] positions, 3k [[Nodes per second|nodes per second]] <ref>[https://groups.google.com/d/msg/rec.games.chess/P9WW8L3gq9U/YRX_mZAjv-wJ ACM Tournament - Specs] by Jim Bumgardner, [[Computer Chess Forums|rgc]], June 28, 1994</ref>.
==Selected Games==
<ref>[https://groups.google.com/d/msg/rec.games.chess/KzylHYi4mH0/2_lsGXtxZocJ ACM 1994: Spector's games] by [[Steven Edwards|Steven J. Edwards]], [[Computer Chess Forums|rgc]], June 29, 1994</ref>
===Now===
[[ACM 1994]], round 2, [[Spector]] - [[Now]]
<pre>
[Event "ACM 1994"]
[Site "Cape May, NJ USA"]
[Date "1994.06.25"]
[Round "2"]
[White "Spector"]
[Black "Now"]
[Result "1/2-1/2"]
1.e4 d5 2.exd5 Qxd5 3.Nc3 Qa5 4.Bc4 e6 5.Nf3 Bb4 6.O-O Nf6 7.a3 O-O 8.Rb1 Be7
9.b4 Qf5 10.Nb5 Na6 11.Nbd4 Qg4 12.h3 Qh5 13.Bxa6 bxa6 14.Nc6 Bd6 15.Nfe5 Bxe5
16.Qxh5 Nxh5 17.Nxe5 f6 18.Nd3 e5 19.Nc5 Nf4 20.d3 Ne2+ 21.Kh1 Nd4 22.c3 Ne6
23.Ne4 Rd8 24.Rd1 a5 25.Be3 f5 26.Nc5 f4 27.Bc1 Nxc5 28.bxc5 f3 29.g4 Ba6 30.d4
Be2 31.Rd2 Rab8 32.Rxb8 Rxb8 33.Rb2 Rxb2 34.Bxb2 h5 35.dxe5 hxg4 36.hxg4 Bc4
37.Kh2 Kf7 38.Kg3 Ke6 39.Kf4 Kd5 40.Bc1 a4 41.Kxf3 Kxe5 42.Bf4+ Kd5 43.Bxc7 Kxc5
44.Be5 Bd5+ 45.Kf4 g6 46.Bd4+ Kc4 47.Bxa7 Kb3 48.Bc5 Kxc3 49.Ke3 Kc4 50.Be7 Bc6
51.f3 Bb5 52.Ke4 Bc6+ 53.Kf4 Kd3 54.Kg3 Bd5 55.Kf2 1/2-1/2
</pre>
===Evaluator===
[[ACM 1994]], round 3, [[Evaluator]] - [[Spector]]
<pre>
[Event "ACM 1994"]
[Site "Cape May, NJ USA"]
[Date "1994.06.26"]
[Round "3"]
[White "Evaluator"]
[Black "Spector"]
[Result "1-0"]
1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 a6 6.Bg5 e6 7.f4 Be7 8.Qf3 Qc7
9.O-O-O Nbd7 10.Be2 b5 11.Kb1 Bb7 12.a3 O-O 13.Qe3 h6 14.Bxf6 Bxf6 15.g3 e5
16.Nf5 exf4 17.gxf4 Bxc3 18.bxc3 Qc5 19.Qg3 g6 20.Rxd6 Kh8 21.Qh4 h5 22.Bxh5
Qf2 23.Qxf2 Nf6 24.Qd4 1-0
</pre>
=Description=
<ref>refers to the published 1996 version</ref>
==Board Representation==
Spector maintains a [[Bitboard Board-Definition|bitboard board-definition]] and an [[8x8 Board|8x8 board]], and further [[Incremental Updates|incrementally updates]] [[Attack and Defend Maps|attack tables]], attack-to, attack-from, and combined attack bitboards.
===Bitboards===
In the pre-[https://en.wikipedia.org/wiki/C99 C99] days, without 64-bit data type, [[Bitboards|bitboards]] were often defined as union of [[Byte|byte]]-, [[Word|word]]- and [[Double Word|double word]] [[Array|arrays]].
<pre>
typedef unsigned short int ustdwiT;
typedef unsigned long int ustdsiT;
#define byteW 8
#define wordW 16
#define dwrdW 32
#define qwrdW 64
/* the bitboard */
#define bbcvL (qwrdL / byteL)
typedef byteT bbcvT[bbcvL];
#define bbwvL (qwrdL / wordL)
typedef ustdwiT bbwvT[bbwvL];
#define bbsvL (qwrdL / dwrdL)
typedef ustdsiT bbsvT[bbsvL];
typedef union bbU {
bbcvT bbcv; /* unsigned characters/bytes (8 bits) */
bbwvT bbwv; /* unsigned word integers (16 bits) */
bbsvT bbsv; /* unsigned short integers (32 bits) */
} bbT, *bbptrT;
</pre>
<span id="BitScan"></span>
'''BitScan'''
The divide and conquer [[BitScan#BitscanwithReset|bitscan with reset]] [https://en.wikipedia.org/wiki/C_preprocessor macro] with word lookups is used to [[Bitboard Serialization|serialize bitboards]], and applies the [https://en.wikipedia.org/wiki/Comma_operator comma operator] to "return" a boolean result whether the bitboard is empty (0) or not (1):
<pre>
#define bb_next(bb, sq) \
(bb.bbsv[0] ? \
(bb.bbwv[0] ? \
((bb.bbwv[0] &= canwv[sq = *(bfvbase + bb.bbwv[0])]), \
(sq += sq_a1), 1) \
: \
((bb.bbwv[1] &= canwv[sq = *(bfvbase + bb.bbwv[1])]), \
(sq += sq_a3), 1)) \
: \
(bb.bbsv[1] ? \
(bb.bbwv[2] ? \
((bb.bbwv[2] &= canwv[sq = *(bfvbase + bb.bbwv[2])]), \
(sq += sq_a5), 1) \
: \
((bb.bbwv[3] &= canwv[sq = *(bfvbase + bb.bbwv[3])]), \
(sq += sq_a7), 1)) \
: \
((sq = sq_nil), 0)))
#define bb_next_gp(sq) bb_next(gp_bb, sq)
</pre>
<span id="PopCount"></span>
'''Population Count'''
[[Population Count|Population count]] is implemented as sum of four word lookups.
<pre>
#define bb_count(bb) \
(*(bevbase + bb.bbwv[0]) + *(bevbase + bb.bbwv[1]) + \
*(bevbase + bb.bbwv[2]) + *(bevbase + bb.bbwv[3]))
</pre>
===8x8 Board===
Beside bitboards, a regular [[8x8 Board|8x8 board]] is maintained, a union of two- and one-dimensional arrays:
<pre>
/* regular board */
typedef union rbU
{
cpT rbm[rankL][fileL]; /* rank/file indexing */
cpT rbv[sqL]; /* square indexing */
} rbT, *rbptrT;
</pre>
===Move-Generation===
[[Move Generation|Move generation]] utilizes the [[Attack and Defend Maps|attack tables]], is staged, and generates strictly [[Legal Move|legal moves]].
==Search==
Spector performs a [[Principal Variation Search|principal variation search]] with [[Transposition Table|transposition table]] and [[Null Move Pruning|recursive null move pruning]] of [[Depth Reduction R|R==3]] inside an [[Iterative Deepening|iterative deepening]] framework. [[Check Extensions|Checks]], [[One Reply Extensions|singular check responses]], [[Passed Pawn Extensions|pawn to seventh rank]], and [[Recapture Extensions|recaptures]] are [[Extensions|extended]] by one [[Ply|ply]], [[Double Check|double]] and [[Discovered Check|discovered checks]] even by two. The [[Killer Heuristic|killer heuristic]] and [[Last Best Reply]] improve [[Move Ordering|move ordering]].
==Evaluation==
Beside [[Material#Balance|material balance]], Spector considers various first order terms by traversing all pieces and calling piece specific functions. [[King Safety|King safety]] takes [[King Safety#KingTropism|piece tropism]], [[King Safety#PawnShield|pawn shield]] and multiple attacks into account, while in the [[Endgame|endgame]] [[King Centralization|centralization]] and [[King Pawn Tropism|King pawn tropism]] starts to dominate. [[Pawn Structure|Pawn structure]] evaluation focuses on [[Passed Pawn|passed pawns]], considering advancement, [[Blockade of Stop|blockade]] and [[Control of Stop and Telestop|control of stop]]. Remaining piece considerations include [[Development|development]], [[Square Control|square control]], and some [[Tactics|tactical]] terms such as penalties for [[Pin|pinned]] and [[Hanging Piece|hanging pieces]].
=See also=
* [[CookieCat]]
* [[Edwards' Tablebases]]
* [[Last Best Reply]]
* [[Symbolic]]
=Downloads=
<ref>Courtesy [[Steven Edwards]]</ref>
* [[File:tbgen.zip]]
* [[File:Spector.zip]]
=Forum Posts=
* [https://groups.google.com/d/msg/rec.games.chess/tUnMP5z-O6M/1u3tu4OdoBkJ 24th ACM Computer Chess Championship] by [[Steven Edwards|Steven J. Edwards]], [[Computer Chess Forums|rgc]], June 25, 1994 » [[ACM 1994]]
: [https://groups.google.com/d/msg/rec.games.chess/KzylHYi4mH0/2_lsGXtxZocJ ACM 1994: Spector's games] by [[Steven Edwards|Steven J. Edwards]], [[Computer Chess Forums|rgc]], June 29, 1994
* [http://www.chesscircle.net/forums/archive/index.php/t-37436.html For chess program source collectors] by [[Steven Edwards]], Chess Circle, August 13, 2006
* [http://www.talkchess.com/forum/viewtopic.php?start=9&t=38556&topic_view=flat Testing LBR] by [[Steven Edwards]], [[CCC]], March 27, 2011
* [http://www.talkchess.com/forum/viewtopic.php?t=57486 LMR by another name] by [[Steven Edwards]], [[CCC]], September 02, 2015 » [[Late Move Reductions]]
* [http://www.talkchess.com/forum/viewtopic.php?t=62065&start=20 Re: Steven Edwards RIP...] by [[Michael Byrne|Michael B]], [[CCC]], November 11, 2016
: [http://www.talkchess.com/forum/viewtopic.php?t=62065&start=21 Re: Steven Edwards RIP...] by [[Michael Byrne|Michael B]], [[CCC]], November 11, 2016
=External Links=
* [https://en.wiktionary.org/wiki/spector spector - Wiktionary]
* [https://en.wiktionary.org/wiki/specto specto - Wiktionary]
* [https://en.wikipedia.org/wiki/Spector_%28disambiguation%29 Spector (disambiguation) from Wikipedia]
* [https://en.wikipedia.org/wiki/Spectrum Spectrum from Wikipedia]
* [https://en.wikipedia.org/wiki/Spectrum_%28disambiguation%29 Spectrum (disambiguation) from Wikipedia]
* [https://en.wikipedia.org/wiki/Speculum Speculum from Wikipedia]
* [https://en.wikipedia.org/wiki/Spectator Spectator from Wikipedia]
* [https://en.wikipedia.org/wiki/Speculation Speculation from Wikipedia]
* [https://en.wikipedia.org/wiki/Inspector Inspector from Wikipedia]
* [https://en.wikipedia.org/wiki/Inspector_%28disambiguation%29 Inspector (disambiguation) from Wikipedia]
* [https://en.wikipedia.org/wiki/Inspection Inspection from Wikipedia]
=References=
<references />
'''[[Engines|Up one Level]]'''
[[Category:Open Source]]
