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About Horizon

Horizon is a WinBoard chess engine. If WinBoard is new to you, read the WinBoard FAQ for help installing and configuring it.

Horizon is a joint venture by Ron Murawski (programming), Jim Monaghan (chess advice), Roger Brown (testing), and Ron Winter (programming & programming advice). Jim is also the creator of Horizon's opening book.

Horizon plays well at all time controls. Setting a main hash table size of 32 to 64MB and a pawn hash size of 4 MB works well. Gameplay is aggressive and focused on center control and king attack. The king attack tendency is strong and makes for interesting games, especially against other aggressive engines.

Horizon users are invited to send email: HorizonChess@yahoo.com  Bug reports are especially welcome!

Current Version

Current version is: Horizon 4.3 (release date: December 23, 2005)

The most important changes from the last official release:

• Chess:
• Playing strength now scales well through all time controls
• Time usage extended for problematic positions
• Opening book improved by manually removing blunder moves and poor lines, and manually adding some selected missing lines -- some of these lines go quite deep
• Internal:
• Move ordering improved
  
• Hash replacement logic changed
• Hash aging changed
• Fewer compiler warnings
• Optimizations:
• Search speed increased up to 2x faster (move ordering improvements)
• Features:
• Removed fail-high/ fail-low indicators from score (illegal according to the WinBoard specification although they didn't seem to cause any problems) and added the indicators to pv instead where they are more visible
• Bugfixes:
• Time-loss bug fixed
  
• Fixed bug that was causing random moves during long time-control games

• Endgame play is weak
• Passed pawn play is weak
  
• Ponder is still disabled internally. It will be re-enabled in the next release.
  
• Some opening book lines end too early

Horizon 4.3 is available from the Download page.

Opening Book Description

Opening book date: Dec 18, 2005 -- This book is filtered by ELO with only highly rated players’ games included. The openings were carefully chosen to compliment Horizon’s playing personality. Jim Monaghan created this book. Thanks, Jim! The book has been enhanced by eliminating openings that lead to quick losses and by extending some shorter lines.

Opening book gamebase description:

As White, Horizon will play either 1. c4, 1.e4 or 1.d4; as Black vs. e-pawn Horizon will play the Sicilian or Double-e-pawn; as Black vs. d-pawn Horizon will play the Nimzo/QID structures and Double d-pawn lines. The original book was based on 160,764 white wins and 88,237 black wins. The average Elo for the source pgn was 2500.

Future Plans

There are many remaining areas of future change. Here are some of them:

• Encourage speculative attacks that lose material but win the game
  
• More thorough evaluation of pawn chain structure
• More emphasis on piece mobility
• Implement attack tables
• Multi-probe hash table
• Continue to improve the opening book
  
• Pawn storm knowledge for opposite-side castling
  
• More endgame knowledge
• Improve the search, especially the move ordering
• Squash bugs!
• Rework the entire program for clarity

History

Horizon was born on July 1, 2001. I am counting Horizon's birthday from the day I started writing my first line of code, not from the first release, which was on October 25, 2001 (The same day that Microsoft released Windows XP). Horizon's first release marked it as a promising engine and, with some fits and starts, it has continued to improve. Thanks to all the WinBoarders out there for their interest and thanks especially to all the tournament directors who take the time to play engine tournaments.

Acknowledgements

Horizon runs atop a much-modified version of Colin Frayn's and Dann Corbit's open-source Beowulf infrastructure. I would not have created Horizon without Colin's and Dann's kind permission to do so. I thank them for making the Beowulf code open source and for allowing me the privilege to extend and change this codebase. If Horizon plays well, then certainly Colin's and Dann's efforts deserve much credit. Horizon is standing on the shoulders of these two giants. I repay my debt to them by sending them improvements and bugfixes to the Beowulf infrastructure. Please blame all Horizon bugs on me, for they are my responsibility.

Special thanks to:

• Colin Frayn, for creating Beowulf and helping me to understand Beowulf's inner workings
• Jim Monaghan, for his tireless chess advice, his help with the eval, his creating the opening book and, most of all, for becoming my best chess friend. You have stuck with me through thick and thin. Jim, you kept me going at times when I was ready to quit! Thanks!!!
• Dann Corbit, for being his knowledgeable and inimitable self.
• Roger Brown, for testing and for keeping me amused with his sharp-witted humor
• Ron Winter, one of the finest C programmers I've ever known, for his programming help and advice.
• Leo Dijksman, for his testing at long time control, especially with ponder 'on'
• Günther Simon, for his testing at Rapid time control
• Vine Smith, for helping with the eval in the beginning
• Tamim, for his chess advice sharpening Horizon’s king attacking abilities and for his game testing
• Bruce Moreland for his informative chess programming web pages
• Ed Schroeder for his informative chess programming web pages
  
• Bob Hyatt, the dean of chess-programmers, for his wonderful Crafty and all his helpful CCC posts
• Bob Jenkins, for writing the Isaac 64-bit pseudo-random number generator and making it public domain
• ICD Chess, for hosting the CCC

To all WinBoard & WBEC forum posters: I may not respond, but I read EVERYTHING!

Team Horizon, Past and Present

•  

• Ron Murawski -- 07/2001 to present
• Jim Monaghan -- 11/2001 to present
• Roger Brown -- 11/2002 to present
• Ron Winter -- 12/2003 to present
• Tamim -- 07/2002 to present

• Vine Smith -- 07/2001 to 11/2001