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		Ralph William (Bill) Gosper, Jr., an American mathematician and computer scientist, along with Richard Greenblatt considered the co-founder of the hacker community [1] . In the 60s, affiliated with MIT, he worked for Project MAC (Machine-Aided Cognition), where his contributions to computational mathematics and Bit-Twiddling include HAKMEM and Maclisp. He helped Greenblatt with his chess program Mac Hack VI, and operated the PDP-6 when Robert Q played its first tournament game versus Carl Wagner. In the 70s, Bill Gosper moved to Stanford University for some years, where he lectured and helped Donald Knuth to write volume II of The Art of Computer Programming. He has worked at or consulted for Xerox PARC, Symbolics, Wolfram Research, the Lawrence Livermore National Laboratory, and Macsyma [2]. Bill Gosper created numerous packing problem puzzles such as the Twubblesome Twelve [3], and was interested in the Conway's Game of Life, where he found the Glider Gun and originated the Hashlife algorithm to speed up the computation of Life patterns [4].
Bill Gosper 2006 [5]

Robert Q

Allen Moulton and R. William Gosper operating "Robert Q" on a PDP-6 [6] [7]

HAKMEM

HAKMEM, alternatively known as AI Memo 239, is a February 1972 "memo" (technical report) of the MIT AI Lab by Gosper et al. that describes a wide variety of hacks, primarily useful and clever algorithms ^[8], and even a chess position ^{[9] [10]}. A few samples, referred elsewhere:

HAKMEM 70

HAKMEM 70 ^[11], A neat chess problem, swiped from Chess for Fun and Chess for Blood, by Edward Lasker ^[12]. White mates in three moves:

5B2/6P1/1p6/8/1N6/kP6/2K5/8 w - -

HAKMEM 169

HAKMEM 169, to count the ones in a PDP-6/PDP-10 36-bit word, written in Assembly ^{[13] [14]}:

   LDB   B,[014300,,A]     ;or MOVE B,A then LSH B,-1
   AND   B,[333333,,333333]
   SUB   A,B
   LSH   B,-1
   AND   B,[333333,,333333]
   SUBB  A,B               ;each octal digit is replaced by number of 1's in it
   LSH   B,-3
   ADD   A,B
   AND   A,[070707,,070707]
   IDIVI A,77              ;casting out 63.'s

HAKMEM 175

HAKMEM 175 - next higher number with the same number of one bits (Snoob), by Bill Gosper, PDP-6 Assembly ^[15]:

   MOVE  B,A
   MOVN  C,B
   AND   C,B
   ADD   A,C
   MOVE  D,A
   XOR   D,B
   LSH   D,-2
   IDIVM D,C
   IOR   A,C

Gosper's Glider Gun

Gosper's Glider Gun in action — a variation of Conway's Game of Life [16]

See also

• Bit-Twiddling
• Mac Hack VI
• PDP-6
• Traversing Subsets of a Set

Selected Publications

• Michael Beeler, Bill Gosper, Rich Schroeppel (1972). HAKMEM, Memo 239, Artificial Intelligence Laboratory, Massachusetts Institute of Technology ^[17]
• Bill Gosper (1977). Decision procedure for indefinite hypergeometric summation. Proc. Natl. Acad. Sci. USA, Vol. 75, No. 1, pdf ^[18]

External Links

• Bill Gosper from Wikipedia
• Twubblesome Twelve - a difficult puzzle by Bill Gosper
  Rep-tiles by Bill Gosper
• HAKMEM from Wikipedia
  HAKMEMC -- HAKMEM Programming hacks in C by Alan Mycroft
• Gosper's algorithm from Wikipedia
• Gosper curve from Wikipedia
• Hashlife from Wikipedia by Bill Gosper

References

1. ^ Hackers: Heroes of the Computer Revolution
2. ^ Bill Gosper from Wikipedia
3. ^ Twubblesome Twelve - a difficult puzzle by Bill Gosper
4. ^ Gosper's Algorithm (Hashlife) explained
5. ^ Mathematician Bill Gosper in March, 2006 at the Seventh Gathering for Gardner (G4G7) in Atlanta, Georgia, 16 March 2006, Photographer Thane Plambeck
6. ^ MIT Computer Loses to Human in Chess. Sun Journal (Lewiston), January 23, 1967, Google News
7. ^ AP :: Images :: Search Results :: Carl Wagner, 1967, MIT Chess
8. ^ HAKMEM from Wikipedia
9. ^ Michael Beeler, Bill Gosper, Rich Schroeppel (1972). HAKMEM, Memo 239, Artificial Intelligence Laboratory, Massachusetts Institute of Technology
10. ^ HAKMEMC -- HAKMEM Programming hacks in C by Alan Mycroft
11. ^ HAKMEM - GAMES: ITEM 70
12. ^ Edward Lasker (1942,1962) Chess for Fun and Chess for Blood. Dover Publications; 2 edition, ISBN-13: 978-0486201467, amazon
13. ^ HAKMEM 169 by Gosper, Mann, Lenard, [Root and Mann], HAKMEM
14. ^ PDP-10 Machine Language
15. ^ HAKMEM 175 by Bill Gosper
16. ^ Bill Gosper's Glider Gun in action — a variation of Conway's Game of Life. This image was made by using Life32 v2.15 beta by Johan G. Bontes, 2005, Gun (cellular automaton) from Wikipedia
17. ^ Web-available by Henry Baker
18. ^ Gosper's algorithm from Wikipedia

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