1. Introduction

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



Glaurung is a free UCI chess engine.  It is not a complete chess

program, but requires some UCI compatible GUI (like XBoard with

PolyGlot, eboard, José, 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 Glaurung with your

GUI.



Glaurung 2 is a completely rewritten version of Glaurung.  Apart from

the parallel search code, almost no code is shared with Glaurung

1.2.1, the previous stable version.  The new program is clearly

stronger than the old, but has a less attractive style of play,

because there are still a few major holes in its evaluation function

(most notably space and development).



This version of Glaurung 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 Glaurung 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 Glaurung on Unix-like

    systems.  For further information about how to compile Glaurung

    yourself, read section 4 below.



  * MacOSX/, a subdirectory containing excutables for Apple Macintosh

    computers running Mac OS X 10.4 (Tiger) and newer.  There are two

    executables, one for OS X 10.4, and one for OS X 10.5.  The

    executable for OS X 10.4 will work in 10.5 as well, but the one

    for 10.5 is faster.



  * LinuxX86/, a subdirectory containing 32-bit and 64-bit x86 GNU/Linux

    executables.



  * Windows/, a subdirectory containing 32-bit and 64-bit Windows

    executables.



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

    adapter.





3. Opening books

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



This version of Glaurung 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".



A book file contributed by Salvo Spitaleri can be found on the

Glaurung web page.





4. Compiling it yourself

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



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

Glaurung 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

Glaurung 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 Glaurung on certain 64-bit 

systems, regardless of the endianness.  If Glaurung 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 Glaurung 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. 







5. History

----------



2007-05-06: Glaurung 2 - epsilon

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



The first public release, and the first version of my new program

which is able to match the old Glaurung 1.2.1 on a single CPU.  Lots

of features and chess knowledge is still missing.



2007-05-10: Glaurung 2 - epsilon/2

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



This version is very close to 2 - epsilon.  The major changes are:



  * A number of compatibility problems which appeared when trying to

    compile Glaurung 2 - epsilon on various operating systems and CPUs

    have been solved.



  * Fixed a major bug in the detection of rooks trapped inside a

    friendly king.



  * Added knowledge about several types of drawn endgames.



  * Fixed a few FRC related bugs.  FRC now works, but because of

    serious holes in the evaluation function the program plays very

    badly.



  * A slightly more sophisticated king safety evaluation.



2007-06-07: Glaurung 2 - epsilon/3

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



The first public version with support for multiple CPUs.  Unless you

have a dual-core (or better) computer, use Glaurung with a PolyGlot

book, or runs games with ponder on, you may want to skip this version,

which is almost certainly no stronger than 2 - epsilon/2 when running

on a single CPU.  The main changes compared to the previous version

are:



  * Parallel search, with support for 1-4 CPUs.  The program currently

    always allocates a separate pawn hash table and material hash

    table for four threads, which is a pure waste of RAM if your

    computer has just a single CPU.  This will be fixed in a future

    version.



  * Fixed a bug in book randomization.  When using Polyglot books, the

    previous version would always select exactly the same move in the

    same position after a restart of the program.  Thanks to Pavel

    Háse for pointing this out.



  * Fixed a UCI pondering bug: Glaurung no longer instantly prints its

    best move when the maximum depth is reached during a ponder

    search, as the previous version did.  According to the UCI

    protocol, it is not allowed to print the best move before the

    engine has received the "stop" or "quit" command.



  * Additional search information:  The new version displays hash

    saturation and the current line(s) of search.



  * Several minor bug fixes and optimizations in the search and

    evaluation. 



2007-06-08: Glaurung 2 - epsilon/4

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



A bugfix release, with only a single important change:



   * Fixed a very serious pondering bug.  As pointed out by Marc

     Lacrosse, the previous version would lose on time in almost every

     single game with pondering enabled.  The new version handles

     pondering correctly (or so I hope).  When playing with ponder

     off, the new version is identical to version 2 - epsilon/3.



2007-06-25: Glaurung 2 - epsilon/5

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



Another minor update, including the following improvements and bug

fixes:



   * As Werner Schüle discovered, the previous version would sometimes

     stop thinking and lose on time right before delivering checkmate

     (which is of course a very unfortunate moment to lose on time).

     I haven't been able to reproduce Werner's problem on my computer

     (probably because I run a different OS), but I have fixed the bug

     which I suspect caused the time losses.  I hope the time losses

     will no longer occur with 2 - epsilon/5.



   * The program is now slightly less resource-hungry on computers

     with less than 4 CPU cores: The previous version would always

     allocated separate pawn and material hash tables for four

     threads, even when running on a single-core CPU.  The new version

     only allocates pawn and material hash tables for the threads

     which are actually used.



   * A minor reorganization of the memory layout has made the parallel

     search about 10% more efficient (at least on my computer, but the

     results are likely to vary considerably on different systems).



   * The Intel Mac OS X binary is much faster than before, thanks to

     the Intel C++ compiler (previous versions were compiled with

     GCC).



   * A few other very minor bug fixes and enhancements.



2007-11-21: Glaurung 2.0

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



The first stable (or so I hope) and feature-complete version of

Glaurung 2.  The following are the main changes compared to the

previous version:



   * The license has been changed from GPL version 2 to GPL version 3.



   * MultiPV mode.



   * Support for the "searchmoves" option in the UCI "go" command.

     This means that it is possible to ask Glaurung to exclude some

     moves from its analysis, or to restrict its analysis to just a

     handful of moves selected by the user.  This feature must also be

     supported by the GUI under which Glaurung is run.  Glaurung's own

     GUI does currently not support this feature.



   * Chess960 support now works.  The program still plays this game 

     very badly, because of lack of opening knowledge.



   * Much more aggressive pruning in the last few plies of the main

     search.



   * Somewhat better scaling on multi-CPU systems, and support for up

     to 8 CPUs.



   * Lots of new UCI parameters.



   * Improved time managment, especially in games with pondering on 

     (i.e. when the engine is allowed to think when it's the

     opponent's turn to move).



   * Some evaluation improvements, and some new basic endgame

     patterns.



   * The program should no longer crash if the game lasts longer than

     1000 plies.

 

   * Many minor bug fixes and other tiny improvements throughout the

     code.  

 

   * More generously commented code, and numerous cosmetic changes in

     coding style.



2007-11-22: Glaurung 2.0.1

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



   * Fixed (or so I hope) a bug which would occasionally cause one of

     the search threads to get stuck forever in its idle loop.



2008-05-14: Glaurung 2.1

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



This version contains far too many changes to list them all, but most

of them are minor and cosmetic.  The most important and noticable

changes are a lot of new UCI parameters, and many improvements in the

evaluation function.  The highlights are:



   * Extensive changes in the evaluation function.  The addition of

     king safety is the most important improvement, but there are also

     numerous little improvements elsewhere in the evaluation.  There

     is still much work left to do in the evaluation function, though.

     Space and development are still missing, and the tuning is likely

     to be very poor.  Currently, the program is optimized for an

     entertaining style rather than maximum strength.



   * More accurate forward pruning.  The previous version used the

     null move refutation move to improve the pruning accuracy by

     means of a very simple trick: It did not allow pruning of any

     moves with the piece captured by the null move refutation move.

     In Glaurung 2.1, this has been enhanced: It does not allow

     pruning of moves which defend the destination square of the null

     move refutation move, nor of moves which block the ray of the

     piece in the case that the moving piece in the null move

     refutation move is a slider.



   * More conservative use of LMR at PV nodes.  The previous version

     searched the first 6 moves with full depth, 2.1 by default

     searches the first 14 moves with full depth (but there is a new

     UCI parameter for configuring this).  I am not at all sure

     whether this is an improvement.  More thorough testing is

     required. 



   * Feedback from the evaluation to the search.  The search passes an

     object of type 'EvalInfo' to the eval, and the eval fills this

     struct with various potentially useful information (like the sets

     of squares attacked by each piece type, the middle game and

     endgame components of the eval, etc.).  At the moment, almost

     none of this information is actually used by the search.  The

     only exception is that the evaluation function is now used to

     adjust the futility pruning margin in the quiescence search.



   * Less extensions.  This hurts the programs performance a lot in most

     test suites, but I hope it improves the branching factor in deep

     searches.



   * A very long list of new UCI parameters, especially for tuning the

     evaluation. 





6. Terms of use

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



Glaurung 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 Glaurung 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 tord@glaurungchess.com