Atlas

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Atlas, an early chess program written in 1967 by Alex Bell at Atlas Computer Laboratory, Chilton. It was basically a resurrected, cleaned up Algol version of Bell's and Barricelli's old program from the early 60s to test evolutionary theories, which had an evaluation function based purely on mobility - at that time the first fully legal chess program to run in England, and likely also the base of Barricelli's WCCC 1974 entry Freedom.

Atlas, running on an ICL Atlas computer, looked three plies ahead with alpha-beta, and would accept almost any captures in that depth with weighting on swaps of the more powerful pieces, i.e. it would always swap a queen for a queen. If no captures were present it prepared to castle or mini-maximised its mobility. A slight modification prevented it from moving its queen in the first 5 moves. Atlas played a few sparring games against Lancaster, John Scott's program, then dubbed "Scott" , and largely suffered from horizon effect. =Move Generation= A description of Atlas' move generation techniques along with a mate-in-two solver is given with Algol source code listing in Games Playing with Computers, 3.1 Chess. Atlas uses two distinct 8x8 boards [1:65] and piece lists [O:16] for white and black man with identical piece coding, passing the boards per reference as 'mymanin' or 'opponents' dependent on side to move. Pre-calculated rook and bishop tables contain one vector of direction increments, i.e. east (+1), west (-1), north (+8), and south (-8) for rooks, and further for each square a vector of ray-direction terminal destination squares. The embedded routine 'rookorbishopmove' in scope of the outer move generation routine loops over all four directions, gets increment and terminal target square from the rook or bishop table, and iterates the destination along the ray. Inside the ray-loop it tests whether the target is occupied by an own man, to terminate the ray-loop, otherwise it stores the move, and then tests to break after a capture or even an illegal king capture with an extra exit 'cutoff'. procedure rookorbishopmove(rookorbishop); integer array rookorbishop; begin for j := 0 step 1 until 3 do   begin k := rookorbishop[j]; k is increment: l := rookorbishop[4 * square + j]; l is terminal square for i := square + k step k until l do      begin if mymanin[i] ≠ 0 then goto newdirection; c := c+1; moves[c] := i;       if opponents[i] ≠ 0 then begin if opponents[i] = 6 then goto cutoff else goto newdirection end end; newdirection: end end of rookorbishopmove;

=Master= In the early 70s, Atlas evolved to Master in collaboration with Peter Kent, and later with John Birmingham and chess expert John Waldron, while Alex Bell finally left Chilton.

=Namesake=
 * Atlas by Andrés Manzanares Campillo

=See also=
 * Astronomy
 * Geography
 * Master
 * Mythology

=Publications=
 * Alex Bell (1972). Games Playing with Computers. Allen & Unwin, index
 * Alex Bell (1978). The Machine Plays Chess? Pergamon Press, amazon

=External Links=

Chess Program

 * Games Playing with Computers | Chapter 3: Board Games, in Alex Bell (1972). Games Playing with Computers. Allen & Unwin
 * MASTER at IFIPS. Excerpt from Alex Bell (1978). The Machine Plays Chess?. Pergamon Press, hosted by Atlas Computer Laboratory from Rutherford Appleton Laboratory (RAL)

Misc

 * Atlas (computer) from Wikipedia
 * Atlas (disambiguation) from Wikipedia
 * Atlas from Wikipedia
 * Atlas Mountains from Wikipedia
 * Atlas (mythology) from Wikipedia
 * Calypso (mythology) from Wikipedia


 * Farnese Atlas from Wikipedia
 * Atlas (rocket family) from Wikipedia
 * Atlas (star) from Wikipedia
 * Atlas (moon) from Wikipedia
 * Colossochelys atlas from Wikipedia
 * Youn Sun Nah & Ulf Wakenius - Calypso Blues @ Jazz sous les pommiers, May 28, 2011, YouTube Video

=References=

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