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Mac Hack VI was the first chess program which uses a [[Transposition Table|transposition table]], but not yet [[Iterative Deepening|iterative deepening]]. It regular searched five plies plus [[Quiescence Search|quiescence search]] and a conditional intermediate layer if own pieces were [[En prise|en prise]].
In his 1970 paper ''A New Hashing Method with Application for Game Playing'' <ref>[[Albert Zobrist]] ('''1970'''). ''A New Hashing Method with Application for Game Playing''. Technical Report #88, Computer Science Department, [https://de.wikipedia.org/wiki/University_of_Wisconsin%E2%80%93Madison The University of Wisconsin, Madison]], reprinted ('''1990''') in [[ICGA Journal#13_2|ICCA Journal, Vol. 13, No. 2]], [http://www.cs.wisc.edu/techreports/1970/TR88.pdf pdf]</ref>, where he introduced [[Zobrist Hashing|Zobrist hashing]], [[Albert Zobrist]] mentions a possible hashing method to obtain an integer which describes the board configuration, and then to [https://en.wikipedia.org/wiki/Division_algorithm divide] the integer by the hash table size and use the [https://en.wikipedia.org/wiki/Remainder remainder] as hash address and the [https://en.wikipedia.org/wiki/Quotient quotient] as key. However, the integer which describes the board may occupy many computer words, and the divide will be complicated and slow. Further the quotient may occupy several words as well, thus most of the transposition table would be occupied by these keys if [[Transposition Table#KeyCollisions|type 1 errors]] were to be avoided. While Zobrist mentions Mac Hack VI used a 32K hash table, he does not made it explicit that Mac Hack used this divide technique. More recently, [[Robert Hyatt]], who had a chance to talk with Greenblatt several times, mentioned Mac Hack's hash function used a series of xor operations on occupied squares <ref> [http://www.talkchess.com/forum3/viewtopic.php?f=10&t=73644&start=50 Re: What are you allowed to learn from a GPL engine (eg. Stockfish) ?] by [[Robert Hyatt]], [[CCC]], June 02, 2020 (Engine Origins requires registration)</ref>.
=<span id="TypeB"></span>Type B=
And so then as word got around- Well, there was a guy a MIT in those days named Hubert Dreyfus, who was a prominent critic of artificial intelligent, and made some statements of the form, you know, computers will never be any good for chess, and so forth. And, of course, he was, again, very romanticized. He was not a strong chess player. However, he thought he was, or I guess he knew was wasn’t world class, but he thought he was a lot better than he was. So anyway, I had this chess program and basically [[Mathematician#Sussman|Jerry Sussman]], who’s a professor at MIT now, and who was also a member of our group, had played. It was around and it was available on the machine. People played it, and so forth. And basically Sussman brought over Dreyfus and said, well, how would you like to have a friendly game or something. Dreyfus said, oh, sure. And sure enough, Dreyfus sat down and got beat. So this immediately got quite a bit of publicity.
[[Herbert Simon]], an AI pioneer, watched the match. He said <ref>[http://www.chess.com/article/view/machack-attack Mac Hack Attack] by [[Bill Wall]], [https://en.wikipedia.org/wiki/Chess.com/ [Chess.com]], May 13, 2008</ref> :
It was a wonderful game - a real cliffhanger between two woodpushers with bursts of insights and fiendish plans ... great moments of drama and disaster that go in such games.
* [http://collection.maynardhistory.org/items/show/5459 CHESS HOW Printout - 1979 · Maynard Historical Society Archives]
* [http://web.archive.org/web/20071221115817/http://classicchess.googlepages.com/Chess.htm Classic Computer Chess - ... The programs of yesteryear] by [[Carey Bloodworth|Carey]], hosted by the [https://en.wikipedia.org/wiki/Internet_Archive Internet Archive] <ref>[http://www.talkchess.com/forum/viewtopic.php?t=56938&start=2 Re: Old programs CHAOS and USC] by [[Dann Corbit]], [[CCC]], July 11, 2015</ref>
* [http://www.chess.com/article/view/machack-attack Mac Hack Attack] by [[Bill Wall]], [https://en.wikipedia.org/wiki/Chess.com/ [Chess.com]], May 13, 2008
* [http://ljkrakauer.com/LJK/60s/machack.htm Mac Hack VI competes] by [[Lawrence J. Krakauer]]
* [http://ljkrakauer.com/LJK/60s/chess1.htm Chess stories] by [[Lawrence J. Krakauer]]
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