Small Potato - xboard/winboard compatible chess engine

A chess engine, like Crafty or gnuchess or Fruit, but much weaker. It would probably rate around 2100 on five-minute games.

Book (for versions 0.6.900 and up):

• 64-bit: http://organicrobot.com/smallpotato/book64.opn.bz2 or http://organicrobot.com/smallpotato/book64.zip
• 32-bit: http://organicrobot.com/smallpotato/book32.opn.bz2 or http://organicrobot.com/smallpotato/book32.zip

Old Windows binaries: http://organicrobot.com/smallpotato/smallpotato061.zip
Old book (versions up to 0.6.1): http://organicrobot.com/smallpotato/book32-0.6.1.zip or http://organicrobot.com/smallpotato/book32-0.6.1.opn.bz2

Uncompress the book and put in the same directory as the binary.

To run using xboard as a frontend, use
xboard -fcp smallpotato
To run it through WinBoard, you will need to add something like the following to your winboard.ini:
/fcp smallpotato /fd "full\path\to\smallpotato\directory"
/scp smallpotato /sd "full\path\to\smallpotato\directory"

Change engine settings by editing sp.rc

For the chess-engine enthusiast, it implements:

• Negascout
• Transposition table
• Quiescent search
• Null-move pruning
• History move ordering
• Run-time configurable value tables

More information on the README

30/01/2014 - 0.7.0

• Works on 64-bit systems
• Extremely minor tweaking of evaluation (of most likely no consequence)
• Fixed a bug where it could make an illegal move on the 50th move of a 50-move draw.
• Note that the book format changed. Books are also not interchangeable between 32- and 64-bit systems

25/09/2003 - 0.6.1

• Tweaked move ordering (including addition of killer move heuristic)
• Minor tweaking of evaluation (with unknown consequences)
• More configurable settings
• Removed MTD(f) and standard alpha-beta search as search options
• Bugfixes (including K v K draw claim)

17/09/2002 - 0.6.0

• Added null-move pruning and aspiration window.
• Improved endgame evaluation (or, more precisely, it now has a separate endgame evaluation). Same with king execution phase.
• Now claims draw on insufficient material.
• Slightly friendlier command line mode.
• Minor bugfixes (fen/epd parsing).

18/08/2002 - 0.5.1

• Now can be configured through file.
• It can now resign.
• Switched, and very slightly tweaked, default evaluation function.
• Speeded up by about 20%.

03/08/2002 - 0.5.0

• Switched default search algorithm to negascout
• Now recover a PV line for display
• Minor transposition table tweaking
• Minor fixes of bugs introduced in 0.4.0
• Now compiles out-of-the-box in clig-less systems.

17/07/2002 - 0.4.0

• Implemented move now and analyze.
• Switched to 0x88 move generation.

11/04/2002 - 0.3.3

• Added opening book.
• EPD suites and lines can be solved
• Made it portable to cygwin
• Changed default hashtable size to 32MB.
• Can now specify hashtable size in kilobytes.
• Made aleweights.out be loaded by default

03/04/2002 - 0.3.2

• No changes (reflex action release that shouldn't have
• happened due to unkown last release)

08/03/2002 - 0.3.1

• Changed to delayed checking of check for speculated performance improvement (even though it does not seem to have materialised)
• Got rid of a couple of often used functions with array lookups for definite performance gains.
• Completed switch to move/unmove.

26/02/2002 - 0.3.0

• Changed name to Small Potato
• Changed to move/unmove instead of move/copy struct (faster)
• Implemented undo and remove for xboard/protocol 2 programs
• (Note: Search instability noted in previous version is "meant" to be there. Caused by the nature of transposition tables, not by some bug in implementation)
• No bugfixes

07/11/2001 - 0.2.4

• Better randomised play
• Switched to 64-bit random hashes
• Lots of bugfixes, including the crash on start introduced in v0.2.3, PGN output bugfixes, and some silliness in QuiescentSearch.
• (NOTE: Search instability still there)

20/10/2001 - 0.2.3

• Added history ordering
• Better time management.
• PGN output for game recording.
• Bugfixes

13/10/2001 - 0.2.2

• Changed GPL license
• Added quiescent search
• Bugfixes

09/10/2001 - 0.2.1

• Added internal iterative deepening
• Bugfixes

03/10/2001 - 0.2.0

• Switched to MTD(f)
• Bugfixes

01/10/2001 - 0.1.5

• Bit of documentation.
• Fixed the hashtable (maybe)

01/10/2001 - 0.1.4

• Improved packaging.
• Couple of bugfixes.

16/04/2001 - 0.1.3

• Switched to Zobrist hashing.
• Switched to negamax
• Added runtime evaluation board loading
• Lots of bugfixes (especially hashtable)

14/03/2001 - 0.1.2

• Added hashtable.
• Lots of bugfixes.

14/02/2001 - 0.1.1

• Added first move move ordering.
• Improved FICS automation.
• Better logging and recording
• Lots of bugfixes

25/12/2000 - 0.1.0

• Initial release

Comments, code, bugreports and patches are welcome.

Copyright (C) 2000 Alejandro Dubrovsky

Small Potato is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; version 2 of the License.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA