### Overview
+[](https://travis-ci.org/official-stockfish/Stockfish)
+[](https://ci.appveyor.com/project/mcostalba/stockfish)
+
Stockfish is a free UCI chess engine derived from Glaurung 2.1. It is
not a complete chess program and requires some UCI-compatible GUI
(e.g. XBoard with PolyGlot, eboard, Arena, Sigma Chess, Shredder, Chess
documentation for your GUI of choice for information about how to use
Stockfish with it.
-This version of Stockfish supports up to 64 CPUs. The engine defaults
-to one search thread it is therefore recommended to inspect the value of
+This version of Stockfish supports up to 128 cores. The engine defaults
+to one search thread, so 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.
+This version of Stockfish has support for Syzygybases.
+
### Files
* 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 below.
+ that can be used to compile Stockfish on Unix-like systems.
+
+
+### Syzygybases
+
+**Configuration**
+
+Syzygybases are configured using the UCI options "SyzygyPath",
+"SyzygyProbeDepth", "Syzygy50MoveRule" and "SyzygyProbeLimit".
+
+The option "SyzygyPath" should be set to the directory or directories that
+contain the .rtbw and .rtbz files. Multiple directories should be
+separated by ";" on Windows and by ":" on Unix-based operating systems.
+**Do not use spaces around the ";" or ":".**
+
+Example: `C:\tablebases\wdl345;C:\tablebases\wdl6;D:\tablebases\dtz345;D:\tablebases\dtz6`
+
+It is recommended to store .rtbw files on an SSD. There is no loss in
+storing the .rtbz files on a regular HD.
+
+Increasing the "SyzygyProbeDepth" option lets the engine probe less
+aggressively. Set this option to a higher value if you experience too much
+slowdown (in terms of nps) due to TB probing.
+
+Set the "Syzygy50MoveRule" option to false if you want tablebase positions
+that are drawn by the 50-move rule to count as win or loss. This may be useful
+for correspondence games (because of tablebase adjudication).
- * polyglot.ini, for using Stockfish with Fabien Letouzey's PolyGlot
- adapter.
+The "SyzygyProbeLimit" option should normally be left at its default value.
+**What to expect**
+If the engine is searching a position that is not in the tablebases (e.g.
+a position with 7 pieces), it will access the tablebases during the search.
+If the engine reports a very large score (typically 123.xx), this means
+that it has found a winning line into a tablebase position.
-### Opening books
+If the engine is given a position to search that is in the tablebases, it
+will use the tablebases at the beginning of the search to preselect all
+good moves, i.e. all moves that preserve the win or preserve the draw while
+taking into account the 50-move rule.
+It will then perform a search only on those moves. **The engine will not move
+immediately**, unless there is only a single good move. **The engine likely
+will not report a mate score even if the position is known to be won.**
-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 *Book File*
-UCI parameter.
+It is therefore clear that behaviour is not identical to what one might
+be used to with Nalimov tablebases. There are technical reasons for this
+difference, the main technical reason being that Nalimov tablebases use the
+DTM metric (distance-to-mate), while Syzygybases use a variation of the
+DTZ metric (distance-to-zero, zero meaning any move that resets the 50-move
+counter). This special metric is one of the reasons that Syzygybases are
+more compact than Nalimov tablebases, while still storing all information
+needed for optimal play and in addition being able to take into account
+the 50-move rule.
### Compiling it yourself
instruction, big-endian machines such as Power PC, and other platforms.
In general it is recommended to run `make help` to see a list of make
-targets with corresponding descriptions. When not using Makefile to
+targets with corresponding descriptions. When not using the Makefile to
compile (for instance with Microsoft MSVC) you need to manually
set/unset some switches in the compiler command line; see file *types.h*
for a quick reference.
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*
+*Copying.txt*.
projects / stockfish / blobdiff