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, 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 32 CPUs, but has not been tested
thoroughly with more than 4.  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 eight threads, it is recommended to raise the value of
"Min Split Depth" UCI parameter to 7.


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 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.

Stockfish has support for 32 or 64 bits CPUS, big-endian machines, like
Power PC, hardware POPCNT instruction and other platforms.

In general is recommended to run 'make help' to see a list of make targets
with corresponding descriptions. When not using Makefile to compile, for
instance with Microsoft MSVC, you need to manually set/unset in the compiler
command line some swicthes, see file types.h for a quick reference.


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.