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SCP, (Stanback Chess Program, also mentioned as JSCP)
an open source chess program by John Stanback, written in C and published in May 1987 at comp.sources.games ^[1]. SCP later evolved to GNU Chess 2-4, and was also ported to the Amiga as Chess and Chess 2.0, the latter with a mouse-driven GUI ^[2]. A WinBoard compatible version of SCP was most recently updated by Jim Ablett ^[3], hosted by Kirill Kryukov ^[4].

Description

Search

SCP represents the board as 12x12 mailbox array with piece lists, and uses full-width alpha-beta with extensions on checks, check evasions, promotions, threats and threats to multiple pieces. Capture sequences are handled by a separate search routine.

Repetitions

SCP seems to originate the repetition counting algorithm, also found in some GNU Chess versions, TSCP ^[5], and Belzebub. It may detect false repetitions in case of exchanging two unequal pieces ^[6].

  for (i = GameCnt; i > Game50; i--)  {
    m = GameList[i]; f = m>>8; t = m & 0xFF;
    if (t != 255 && f != 255) {
      b[f]++; b[t]--;
      if (b[f] == 0) c--; else c++;
      if (b[t] == 0) c--; else c++;
      if (c == 0) r++;
    }
  }

Evaluation

SCP's evaluation considers material, piece-square tables for knights, bishops and passed pawns, piece mobility, pawn structure, rook on (half) open files, and some king safety issues and positive king centre proximity in the endgame.

Publications

• Gerald Tesauro (2001). Comparison Training of Chess Evaluation Functions. In Johannes Fürnkranz, Miroslav Kubat (eds.) (2001). Machines that learn to play games, 117–130, Nova Science Publishers » Automated Tuning, Deep Blue

See also

• Acronym
• GNU Chess
• TSCP
• Zarkov

Forum Posts

• v01i023: chess - C source for chess by John Stanback, comp.sources.games, May 21, 1987
• SCP: ANSI C chess program package available via ftp by Steven Edwards, rec.games.chess, December 26, 1993
• SCP source now at my site by Pete Galati, CCC, October 19, 1999
• Winboard compatible version of SCP? by Scott Ludwig, CCC, January 03, 2000
• An Oldie, but a Goodie: Port of ancient SCP program plays itself... by Dann Corbit, CCC, May 10, 2001
• SCP 1.0d update by Jim Ablett, CCC, June 11, 2007
• SCP/Gnuchess 2.02 JA by John Stanback - Update by Jim Ablett, CCC, July 25, 2009

External Links

• John Stanback's Home Page
• Classic Computer Chess - ... The programs of yesteryear by Carey, hosted by the Internet Archive ^[7]
• SCP maintained and updated by Jim Ablett, hosted by Kirill Kryukov
• Chess for Amiga (1987), MobyGames
• Chess 2.0 for Amiga (1989), MobyGames

References

1. ^ v01i023: chess - C source for chess by John Stanback, comp.sources.games, May 21, 1987
2. ^ Chess 2.0 for Amiga (1989), MobyGames
3. ^ SCP/Gnuchess 2.02 JA by John Stanback - Update by Jim Ablett, CCC, July 25, 2009
4. ^ SCP maintained and updated by Jim Ablett, hosted by Kirill Kryukov
5. ^ Re: Detecting three-fold repetition? by John Stanback, CCC, July 17, 2000
6. ^ Re: Move Tables - explain as if I'm five by Karlo Bala Jr., CCC, November 05, 2012
7. ^ Re: Old programs CHAOS and USC by Dann Corbit, CCC, July 11, 2015

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