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. If you are using more than four threads, it
is recommended to raise the value of "Minimum Split Depth" UCI parameter
to 6.




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.



Stockfish has POPCNT instruction runtime detection and support. This can

give an extra speed on Core i7 or similar systems. To enable this feature

(disabled by default) simply uncomment #define USE_POPCNT in bitcount.h

before to compile.



On 64 bit Unix-like systems the 'bsfq' assembly instruction will be used

for bit counting. Detection is automatic at compile time, but in case you

experience compile problems you can comment out #define USE_BSFQ line in types.h





5. 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.





6. Feedback

-----------



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