MSB, bit 7 is the piece color, x = 0 for white and x = 1 for black pieces. While LSB, bit 0, acts as piece indicator - set for any piece, the lower nibble already contains their point value equivalence in a {1,3,3,5,9,15} solution, luckily all values odd. The bits 1 to 4 (or even 0 to 4) may act as table index for move generation purpose, similar, bit 4 and 5 enumerate to the four possibly useful states of {sliding piece, pawn, king, knight}. However, the leading code saving trick in conjunction with bit 6 after loading the code into the accumulator and shifting it left one (SLA) , is to use disjoint Z80processor flags[9] with four conditional jumps in the right order for up to five cases to distinguish. Zero flag is set for empty squares, parity (odd) for squares off the board, sign flag in case of a king, carry for black pieces and white pieces otherwise.
LDA A,(SQUARE) ; get piece code to Accu (A)
SLA A ; A := A << 1
JP Z, EMPTY ; if ( A == 0 ) empty square
JP PO, OFFBOARD ; else if ( parity(A) is odd ) off the board
JP M, KING ; else if ( A < 0 ) occupied by king
JP C, BLACK ; else if ( carry ) occupied by black piece
JP WHITE ; else occupied by white piece
How it began
Wim Rens in his June 1981 Databus article Grondslagen van computerschaak on how it began with Microtrend and Gambiet [10]:
The second milestone of Gambiet's triumph[11]was achieved under the watchful eye of the firm Microtrend. At home of one of their directors were two TSR-80's, one running Sargon II, the other Gabmol[12]. Microtrend was looking for a chess game in their collection, and end of June a decision was made and a contract placed. The result was impressive: two equally fast Tandy computers and Gambiet had no trouble with the once-famous Sargon.
^ Free translation from Dutch, excerpt from: Wim Rens (1981). Grondslagen van computerschaak. Databus 06-81, pp. 13-15, pdf hosted by Hein Veldhuis (Dutch)
^ first milestone was winning a match from IGM in early 1980
a chess program by Wim Rens, initially written in Z80 assembly to run on a TRS-80 [1], and the first Dutch commercial chess program, merchandised through Microtrend [2]. Gambiet 80 played the first WMCCC 1980 in London, where it finished third with 3/5, and further the European MCC 1981 and European MCC 1982 [3], and the first three Dutch Computer Chess Championships. Gambiet 81 was runner-up behind YNCT 1.0 at the DOCCC 1981, and Gambiet 82 did even better, winning the DOCCC 1982 [4] running on a Xerox Star. Gambiet 83 played the DOCCC 1983 with a fifth place.
Gambiet was base of Microtrend Experimental, which also played the European MCC 1981 with its brother, and was further commercialized in 1982 for the Philips Videopac G7000 video game console, as Videopac C 7010 chess module [5] with its own Z80-compatible NSC800 CMOS microprocessor [6].
Table of Contents
Description
Gambiet is a Shannon Type-A Stategy program, performing alpha-beta with a classical mailbox board representation and following byte-wise piece coding optimized for efficiency [8] :MSB, bit 7 is the piece color, x = 0 for white and x = 1 for black pieces. While LSB, bit 0, acts as piece indicator - set for any piece, the lower nibble already contains their point value equivalence in a {1,3,3,5,9,15} solution, luckily all values odd. The bits 1 to 4 (or even 0 to 4) may act as table index for move generation purpose, similar, bit 4 and 5 enumerate to the four possibly useful states of {sliding piece, pawn, king, knight}. However, the leading code saving trick in conjunction with bit 6 after loading the code into the accumulator and shifting it left one (SLA) , is to use disjoint Z80 processor flags [9] with four conditional jumps in the right order for up to five cases to distinguish. Zero flag is set for empty squares, parity (odd) for squares off the board, sign flag in case of a king, carry for black pieces and white pieces otherwise.
How it began
Wim Rens in his June 1981 Databus article Grondslagen van computerschaak on how it began with Microtrend and Gambiet [10]:Microtrend
According to Trademarkia, GAMBIET was trademark by Microtrend International B.V. in Amsterdam, filed October 26, 1981, as United States trademark, canceled September 13, 1989 [13].Selected Games
WMCCC 1980
WMCCC 1980, round 3, Gambiet 80 - Sargon 2.5 Auto RB [15]DOCCC 1982
DOCCC 1982, round 8, upcoming tournament winner Gambiet 82 loses from newcomer Rebel [16]See also
Publications
External Links
References
© 1982 N.V. Philips Gloeilampenfabrieken - Holland
© 1982 Wim Rens, Microtrend International - Holland
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