1. Introduction

---------------



Stockfish is a free UCI chess engine derived from Glaurung 2.1. It is

not a complete chess program, but requires some UCI compatible GUI

(like XBoard with PolyGlot, eboard, Jos�, Arena, Sigma Chess, Shredder,

Chess Partner, or Fritz) in order to be used comfortably.  Read the

documentation for your GUI of choice for information about how to use

Stockfish with your GUI.



This version of Stockfish supports up to 8 CPUs, but has not been

tested thoroughly with more than 2.  The program tries to detect the

number of CPUs on your computer and set the number of search threads

accordingly, but please be aware that the detection is not always

correct.  It is therefore recommended to inspect the value of the

"Threads" UCI parameter, and to make sure it equals the number of CPU

cores on your computer.





2. Files

--------



This distribution of Stockfish consists of the following files:



  * Readme.txt, the file you are currently reading.



  * Copying.txt, a text file containing the GNU General Public

    License.



  * src/, a subdirectory containing the full source code, including a

    Makefile that can be used to compile Stockfish on Unix-like

    systems.  For further information about how to compile Stockfish

    yourself, read section 4 below.



  * polyglot.ini, for using Stockfish with Fabien Letouzey's PolyGlot

    adapter.





3. Opening books

----------------



This version of Stockfish has experimental support for PolyGlot opening

books. For information about how to create such books, consult the

PolyGlot documentation.  The book file can be selected by setting the

UCI parameter "Book File".







4. Compiling it yourself

------------------------



On Unix-like systems, it should usually be possible to compile

Stockfish directly from the source code with the included Makefile.

The exception is computer with big-endian CPUs, like PowerPC

Macintoshes. Some of the bitboard routines in the current version of

Stockfish are endianness-sensitive, and won't work on a big-endian CPU.

Ensuring that the line with #define USE_32BIT_ATTACKS" near the top

of bitboard.h is commented out should solve this problem.

Commenting out the line with "#define USE_32BIT_ATTACKS" near the



There is also a problem with compiling Stockfish on certain 64-bit

systems, regardless of the endianness.  If Stockfish segfaults

immediately after startup, try to comment out the line with

"#define USE_FOLDED_BITSCAN" near the beginning of bitboard.h and

recompile.



Finally, even if Stockfish does work without any changes on your

computer, it might be possible to improve the performance by changing

some of the #define directives in bitboard.h.  The default settings

are optimized for 64-bit CPUs.  On 32-bit CPUs, it is probably better

to switch on USE_32BIT_ATTACKS, and to use BITCOUNT_SWAR_32 instead of

BITCOUNT_SWAR_64.  For computers with very little memory (like

handheld devices), it is possible to conserve memory by defining

USE_COMPACT_ROOK_ATTACKS.





6. Terms of use

---------------



Stockfish is free, and distributed under the GNU General Public License

(GPL).  Essentially, this means that you are free to do almost exactly

what you want with the program, including distributing it among your

friends, making it available for download from your web site, selling

it (either by itself or as part of some bigger software package), or

using it as the starting point for a software project of your own.



The only real limitation is that whenever you distribute Stockfish in

some way, you must always include the full source code, or a pointer

to where the source code can be found.  If you make any changes to the

source code, these changes must also be made available under the GPL.



For full details, read the copy of the GPL found in the file named

Copying.txt.





7. Feedback

-----------



The author's e-mail address is mcostalba@gmail.com