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Trappy Beowulf

This project is an attempt to modify Beowulf to use [Trappy Minimax]( I started this as a class project for CSc 215 at California State University, Sacramento.

The original readme for Beowulf is included below.

The Beowulf Project

README for Version 2.x.y


(1) About the Beowulf Project
(2) Getting Started
(3) User submissions
(4) Acknowledgements

(1) - About the Beowulf Project

Beowulf is a strong computer chess engine developed primarily by Colin Frayn
(University of Birmingham, UK) and Dann Corbit (USA).  It is a very carefully
designed project with many powerful algorithms designed to be readable and
easily understood even by beginners to the subject.

Beowulf was coded primarily over a two week period in March, 2001.  It was
further honed and improved over the following two months, and released on
May 31st, 2001.  Beowulf is an open source project, the code to which is
freely available to the entire chess programming community provided an
acknowledgement is made either to me, or to the project as a whole.

Beowulf is under continuous development, mainly by Colin Frayn.  Its
strength is difficult to estimate, but recent estimates of version 2.0
have placed it around 2270 ELO (International Master Standard) on a
reasonably fast computer. v2.1 has been running on ICC and achieved a
maximum ELO of over 2500, though this is slightly uncertain and is likely
to be a fairly large overestimate.

The idea behind Beowulf was simple - to produce and distribute a new chess
engine to the entire community which was not only (a) strong, but (b) easy
to understand.  Currently many engines exist in the former category, and
very few in the second.  In my opinion, there are none whatsoever that
fulfil both criteria.  Beowulf hopefully fills that particular gap.

In addition to the source code, my intent was to provide a fully documented
theory page.  There is currently a version up and running at the following

Please let me know if I've missed anything off or anything is
incorrect/unclear. Also let me have any extra submissions that you have
written yourself (although I retain the right to alter or refuse them if I
think they don't fit in too well with the rest of the site or they're
covering points that I have already explained etc....).

The Beowulf home page is here;

This page includes several bits of information about the project, including 
acknowledgements, match and test suite results and a complete version history.

(2) - Getting Started

Beowulf should be rather simple and straightforward to install on any
platform.  The code is almost entirely ANSI compliant, with one or two
exceptions.  There is very little file handling, and at the moment, only a
very small number of complicated features.  Beowulf runs in text mode, and
is also fully compatible with Xboard/Winboard graphical interfaces.

In order to install, the source must be compiled.  If you don't know
how to compile and edit code then you probably shouldn't be playing around
with the source code ;)  Executables can be obtained from Dann Corbit's FTP

and also from the Beowulf home page (see above).

Included in the Beowulf package you should find the entire source code,
including the Nalimov tablebase access code.  You should also find a
small opening book.  I do not provide a Makefile as I have found that the
most efficient compile option is simply to compile the source include file
chess.c on its own with full optimisations.  i.e. for systems using GCC
as their primary compiler, type;

gcc -O3 chess.c -o beowulf -lm

Beowulf reads an opening book format similar to that of ColChess but
slightly more concise.  A larger book is available on the homepage (see
above for the address).  For those of you who wish to create your own books,
there are a few basic features included in Beowulf to allow this, given a
source PGN file.  Several of these can be found on the web with Grandmaster
standard games.

Beowulf can also read a personality file, similar to the file default.per
provided.  It chooses sensible defaults, so you can remove this file totally
if you are not bothered about this feature.  If you want only to change a
few parameters then you only need to list the ones you want to change (the
others will be set to default values).  Do not change the format of the
lines, just the number at the beginning of each line.  These parameters are
clipped if ridiculously large or small values are chosen.  The order of the
entries is not important.

Beowulf can also read Nalimov EGTB files.  These should be either placed in
a subdirectory called 'TB', or in the directory pointed to by any of the
following methods;
(a) Environment variable EGTBPATH
(b) Entry in the config file
(c) Command line parameter TBLOC="c:\path"

The configuration file (beowulf.cfg) should be left in the install directory.
Whenever Beowulf is run from that directory, the configuration file is read
in order to overwrite the default options in the source.  Environment variables
can also be read in to overwrite these configuration file settings.  The only
three supported at the moment are TBPATH, PERSONALITYFILE and BOOKFILE, which
are the directory in which the table bases are stored, and the locations of
your chosen personality file and opening book file respectively.

Finally, a set of command line options can also be issued.  These override
all other settings, and are useful for setting the hash table size for use
in test games.  For a list, try running Beowulf with the command line option
'--help'.  The list is reproduced here for your benefit;

?, help            - Print this file
hash<num>          - Set the hash table size (2^n kb)
tbloc=<directory>  - Set the tablebase location
book=<filename>    - Set the opening book
person=<filename>  - Set the personality file
wskill<num>        - Set the skill level for white (1 to 10)
bskill<num>        - Set the skill level for black (1 to 10)
epdtest=<file>     - Run an EPD test and quit immediately
st<num>            - Set the time per move for an EPD test (default 5s)

Any further questions, feel free to email me at

(3) - User Submissions

If you wish to submit bugfixes or changes to Beowulf, then I'd appreciate if
you could email them to me at the usual address,  In
particular, I'd prefer it if you could email the entire file(s) that you
have changed together with a clear list of the changes made.  Please email
the files as plain text attachments as this is the easiest for me to read.

I welcome any user submissions from competent, experienced programmers.
Beowulf is an ever changing project, and I'd love it if people write their
own functionality into the code.  You will receive a well-earned
acknowledgement both here in this README file, and on the official web page.
If you fix bugs then you will be even more popular.

If you wish to submit a bug report (with no code changes) then please do so
to the same address, with a list of the problems encountered, the platform
on which you were running the code, the compiler used, and the attempts that
you made to fix the problem (especially any that worked).

Many thanks in advance for your help!

(4) - Acknowledgements

I acknowledge the invaluable work of the following people in the Beowulf
project, in no particular order except the first two;

Dann Corbit - Dedicated many many hours work to testing and gave me much invaluable advice.
Ron Murawski - Countless useful comments, mainly on the evaluation code, and a number of substantial rewrites of other sections of the code.
Bob Hyatt - The source code to his strong program Crafty was an invaluable resource when I was in the preliminary stages of coding.
Ernst Heinz - His page on bitboard programming helped me to understand the concept.
Eugene Nalimov - For his incomprehensible, but yet vital endgame tablebase code
Andrew Kadatch - For the compression code which works with the EGTBs
Jim Monaghan - For a great many comments on Beowulf matches, and many tips on improving the engine's strategic play.
Tim Foden - Helped with one or two compatability problems and testing.
Gian-Carlo Pascutto - For many useful comments and suggestions on the code, especially the move ordering.
Remi Coulom - Many useful suggestions and tweaks to the code, especially concerning the hashtable.
Makoto Matsumoto, Takuji Nishhimura and Shawn Cokus - For the random number generation code used in some earlier versions.
Oliver Brausch - For the Bioskey() function, taken from his engine Olithink, with permission.
Jason Carley - For running Beowulf on ICC under the handle 'jc-comp'.
Carlos Justiniano - For his interest in Beowulf through the ChessBrain project.

Enjoy Beowulf!

Colin Frayn

Birmingham, UK
28th January 2004



A modification of the Beowulf chess engine to use Trappy Minimax



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