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Improve the Readme

I tried to improve the Readme because many people in my local
chess club do not understand some of the UCO options properly.
Starting point of this was Cfish's Readme by Ronald de Man,
some internet resources and the Stockfish code itself.

Closes official-stockfish#1898

Initial commit by user @erbsenzaehler, with help from users
Adrian Petrescu, @Alayan-stk-2 and Elvin Liu.

No functional change

Co-Authored-By: Alayan-stk-2 <alayan-stk-2@users.noreply.github.com>
Co-Authored-By: Adrian Petrescu <apetresc@gmail.com>
Co-Authored-By: Elvin Liu <solarlight2@users.noreply.github.com>
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4 people authored and snicolet committed Dec 29, 2018
1 parent 69dc556 commit 800031c94c655e64e436846911e599de6eb35a72
Showing with 117 additions and 50 deletions.
  1. +3 −0 AUTHORS
  2. +114 −50 Readme.md
@@ -6,8 +6,10 @@ Joona Kiiski (zamar)
Gary Linscott (glinscott)

Aditya (absimaldata)
Adrian Petrescu (apetresc)
Ajith Chandy Jose (ajithcj)
Alain Savard (Rocky640)
alayan-stk-2
Alexander Kure
Ali AlZhrani (Cooffe)
Andrew Grant (AndyGrant)
@@ -31,6 +33,7 @@ David Zar
Daylen Yang (daylen)
DiscanX
Eelco de Groot
Elvin Liu (solarlight2)
erbsenzaehler
Ernesto Gatti
Fabian Beuke (madnight)
164 Readme.md
@@ -1,66 +1,112 @@
### Overview
## Overview

[![Build Status](https://travis-ci.org/official-stockfish/Stockfish.svg?branch=master)](https://travis-ci.org/official-stockfish/Stockfish)
[![Build Status](https://ci.appveyor.com/api/projects/status/github/official-stockfish/Stockfish?svg=true)](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
Partner or Fritz) in order to be used comfortably. Read the
documentation for your GUI of choice for information about how to use
[Stockfish](https://stockfishchess.org) is a free, powerful UCI chess engine
derived from Glaurung 2.1. It is not a complete chess program and requires a
UCI-compatible GUI (e.g. XBoard with PolyGlot, Scid, Cute Chess, 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 it.

This version of Stockfish supports up to 512 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
## Files

This distribution of Stockfish consists of the following files:

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

* Copying.txt, a text file containing the GNU General Public License.
* Copying.txt, a text file containing the GNU General Public License version 3.

* src, a subdirectory containing the full source code, including a Makefile
that can be used to compile Stockfish on Unix-like systems.


### Syzygybases
## UCI parameters

Currently, Stockfish has the following UCI options:

* #### Debug Log File
Write all communication to and from the engine into a text file.

* #### Contempt
A positive value for contempt favors middle game positions and avoids draws.

* #### Analysis Contempt
By default, contempt is set to prefer the side to move. Set this option to "White"
or "Black" to analyse with contempt for that side, or "Off" to disable contempt.

* #### Threads
The number of CPU threads used for searching a position. For best performance, set
this equal to the number of CPU cores available.

* #### Hash
The size of the hash table in MB.

* #### Clear Hash
Clear the hash table.

* #### Ponder
Let Stockfish ponder its next move while the opponent is thinking.

* #### MultiPV
Output the N best lines (principal variations, PVs) when searching.
Leave at 1 for best performance.

* #### Skill Level
Lower the Skill Level in order to make Stockfish play weaker.

**Configuration**
* #### Move Overhead
Assume a time delay of x ms due to network and GUI overheads. This is useful to
avoid losses on time in those cases.

Syzygybases are configured using the UCI options "SyzygyPath",
"SyzygyProbeDepth", "Syzygy50MoveRule" and "SyzygyProbeLimit".
* #### Minimum Thinking Time
Search for at least x ms per move.

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 ":".**
* #### Slow Mover
Lower values will make Stockfish take less time in games, higher values will
make it think longer.

Example: `C:\tablebases\wdl345;C:\tablebases\wdl6;D:\tablebases\dtz345;D:\tablebases\dtz6`
* #### nodestime
Tells the engine to use nodes searched instead of wall time to account for
elapsed time. Useful for engine testing.

It is recommended to store .rtbw files on an SSD. There is no loss in
storing the .rtbz files on a regular HD.
* #### UCI_Chess960
An option handled by your GUI. If true, Stockfish will play Chess960.

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.
* #### UCI_AnalyseMode
An option handled by your GUI.

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).
* #### SyzygyPath
Path to the folders/directories storing the Syzygy tablebase files. Multiple
directories are to 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.

The "SyzygyProbeLimit" option should normally be left at its default value.
* #### SyzygyProbeDepth
Minimum remaining search depth for which a position is probed. Set this option
to a higher value to probe less agressively if you experience too much slowdown
(in terms of nps) due to TB probing.

* #### Syzygy50MoveRule
Disable to let fifty-move rule draws detected by Syzygy tablebase probes count
as wins or losses. This is useful for ICCF correspondence games.

* #### SyzygyProbeLimit
Limit Syzygy tablebase probing to positions with at most this many pieces left
(including kings and pawns).


## What to expect from Syzygybases?

**What to expect**
If the engine is searching a position that is not in the tablebases (e.g.
a position with 8 pieces), it will access the tablebases during the search.
If the engine reports a very large score (typically 123.xx), this means
If the engine reports a very large score (typically 153.xx), this means
that it has found a winning line into a tablebase position.

If the engine is given a position to search that is in the tablebases, it
@@ -71,7 +117,7 @@ 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.**

It is therefore clear that behaviour is not identical to what one might
It is therefore clear that this 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
@@ -82,7 +128,7 @@ needed for optimal play and in addition being able to take into account
the 50-move rule.


### Compiling it yourself
## Compiling Stockfish yourself from the sources

On Unix-like systems, it should be possible to compile Stockfish
directly from the source code with the included Makefile.
@@ -96,23 +142,41 @@ 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.

### Resource For Understanding the Code Base

* [Chess Programming Wiki](https://www.chessprogramming.org/Main_Page)
has good overall chess engines explanations
(techniques used here are well explained like hash maps etc), it was
also recommended by the [support team at stockfish.](http://support.stockfishchess.org/discussions/questions/1132-how-to-understand-stockfish-sources)
## Understanding the code base and participating in the project

Stockfish's improvement over the last couple of years has been a great
community effort. There are a few ways to help contribute to its growth.

### Donating hardware

Improving Stockfish requires a massive amount of testing. You can donate
your hardware resources by installing the [Fishtest Worker](https://github.com/glinscott/fishtest/wiki/Running-the-worker)
and view the current tests on [Fishtest](http://tests.stockfishchess.org/tests).

### Improving the code

If you want to help improve the code, there are several valuable ressources:

* [In this wiki,](https://www.chessprogramming.org) many techniques used in
Stockfish are explained with a lot of background information.

* [The section on Stockfish](https://www.chessprogramming.org/Stockfish)
describes many features and techniques used by Stockfish. However, it is
generic rather than being focused on Stockfish's precise implementation.
Nevertheless, a helpful resource.

* [Here](https://www.chessprogramming.org/Stockfish) you can find a set
of features and techniques used by Stockfish and each of them is explained
at the wiki, however, it's a generic way rather than focusing on Stockfish's
own implementation, but it will still help you.
* The latest source can always be found on [GitHub](https://github.com/official-stockfish/Stockfish).
Discussions about Stockfish take place in the [FishCooking](https://groups.google.com/forum/#!forum/fishcooking)
group and engine testing is done on [Fishtest](http://tests.stockfishchess.org/tests).
If you want to help improve Stockfish, please read this [guideline](https://github.com/glinscott/fishtest/wiki/Creating-my-first-test)
first, where the basics of Stockfish development are explained.


### Terms of use
## 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
Stockfish is free, and distributed under the **GNU General Public License version 3**
(GPL v3). 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
@@ -123,5 +187,5 @@ 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
For full details, read the copy of the GPL v3 found in the file named
*Copying.txt*.

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