by Philipp Claßen

About Ghost:

Ghost is a free amateur chess engine written in C++ (download-section)
Ghost was also used as a subject for an important school work (german: "Facharbeit")
The name Ghost was taken from the name of Wolf Larsen's ship in the novel "The Seawolf" by Jack London.

News:

2017-05-30: New releases for Windows are available:
- Ghost 3.1
- Ghost 3.1 (non-POPCNT version) (for older CPUs before 2010)
One critical bug in the evaluation has been fixed. The new version has an improved heuristic for lazy exit tests, which leads to a significant improvement in the overall playing strength.
2017-03-19: 64-bit Windows builds of Ghost 3 are now available:
- Ghost 3.0
- Ghost 3.0 (non-POPCNT version) (for older CPUs before 2010)
2016-10-15: Fixed two critical bugs in the search. The new version of the Beta should be stable, now. See the Ghost 3 page for more details.
2016-09-15: Finally, Ghost 3 enters Beta phase.

Still lots of work to be done but in the meantime you can see updates about Ghost 3 here. There is even a 64-bit Windows binary if you cannot wait and have to try it out immediately.
2014-12-16: Ghost 2.0.2 now ranks at place #130 on the CCRL 40/4 rating list:
- Compared to Ghost 2.0.1 that is a significant improvement of 142 elo.
- Many thanks to Graham Banks for running the gauntlet tournament!
New download options: Arch Linux users can use the AUR package
2014-10-27: Ghost 2.0.2 released (see download-section):
- New optimized builds:
  - Finally, there is a 64-bit Windows executable. In comparison with Ghost 2.0.1 (32-bit), it is about twice as fast.
  - The 64-bit Linux binary should be around 10-20% faster than 2.0.1 (64-bit)
- Usability: By default, optimized search settings are used. Thus, it is no longer necessary to overwrite them with --read-settings
- Backported: Fixes a bug that affects the search. I have discovered it while working on Ghost 3 but I am not certain whether it has significant effects on the playing strength.
2011-03-27: Ghost 2.0.1 currently ranks at place #121 on the CCRL 40/4 rating list:
- 121 Ghost 2.0.1 32-bit 2483 +17 −17 53.5% −26.6 23.3% 1206
- That's an improvement of over 250 elo compared to Ghost 1!
2011-03-25: Ghost 2.0.1 currently ranks at place #145 on the CCRL 40/40 rating list:
- 145-146 Ghost 2.0.1 2405 +32 -32 48.7% +11.1 26.8% 340
- It's also currenty playing test games under 40/4 time limits, with even more promising results so far.
2010-07-14: Ghost 2.0.1 released. An upgrade is highly recommended to benefit from the improved playing strength.
2010-06-29: Ghost 2.0.1beta is available in a Windows version.
- It includes a new settings file that uses a much more selective search and seems to improve playing strength in first tests by roughly 50-100 elo!
- This setting (alternative2.cfg) uses features that won't work with the current linux-version, so it's not recommended to use them under Linux yet.
- However, with the upcoming 2.0.1 version, there will be some additional bug fixes and the new settings will be fully supported in all available versions!
2010-05-09: Fixed the missing version numbers of the engines:
- Ghost 1 has been promoted from 0.14 to 1.0
- Ghost 2 starts with 2.0
There is also an updated build of Ghost 2 for Win32 (using GCC 4.5 under Cygwin).
2010-05-02: No, this site is not dead! As the work on Ghost 3 has been started, it is time for new releases (see download-section):
- The stable Linux version of Ghost 2 (64-bit).
- An slightly outdated Windows binary of Ghost 2 (32-bit). (Unfortunately, the latest code depends on C++0x extensions that are not yet available on Windows.)
- A new 64-bit Linux version of Ghost 1. All fans of this ancient engine should update! (On my two test machines, the 64-bit engine is twice as fast as the 32-bit version).
What has been changed from version 1 to 2? In short, Ghost 2 has been completely rewritten, which greatly improved its playing strength:
- Better evaluation:
  Ghost 2 is capable of playing solid, positional chess, and is less reckless than Ghost 1.
- Improved endgame knowlege:
  The former weakness has become quite a strength, as Ghost 2 should not be underestimated in technical endgames.
- Enhanced search algorithm:
  Although Ghost 2 is a positional chess engine, it is also a better tactician than Ghost 1.
- Additional features:
  - Supports Nalimov tablebases
  - Allows to alter its playing style (try --personality Tal)
In contrast to the major differences between version 1 and 2, Ghost 3 will not be started from scratch. However, the search algorithm definitely needs to be reworked. Ghost 2 uses a MTD(f) algorithm, but it is still open whether Ghost 3 will return to the traditional Negascout. In any case, it will add support for multicore machines.
2004-09-22: Finally, some minor updates on the engine. You can download the new version 0.14 of Ghost 1 in the download-section. There is also a new linux binary for version 0.14. Most changes are related to some bugs in the search function which should be fixed now.
Ghost 1 will not be developed any further except for bugfixes. All efforts will be concentrated on the completely new Ghost 2-version.

About the author of Ghost:

Philipp Claßen
He made his final exam at the "Gymnasium Landau a.d. Isar", Germany.
Performed his civilian service (ger.: Zivildienst) in Straubing, Germany.
Subsequently, he studied computer science at the University of Passau, Germany.
After graduating, he went to Munich and joined a company called Nickwoods, where he developed systems for algorithmic trading (high-frequency trading).
In 2010, he moved to Hamburg to join the software company freiheit.com.
In March 2011, he again relocated to Munich, to work for Mercateo.com, an innovative B2B trading platform.
In April 2017, he joined Cliqz, a startup in Munich. Backed by Mozilla, its mission is to redesign the Internet for the user by combining the power of data, browser, and search.

Search algorithms:

Ghost 3:

MTD(f) search
Multicore support

Internally, it uses work-stealing provided by the Threading Building Blocks library.
Currently, there is still a known scalability bug in my implementation, so the speedup is not optimal (especially on an 8 core machine, where I get only about 5.5x).
I hope that I soon find time to fix the problem. Still, even in its current state, using multiple CPUs leads to a significant improvement in playing strength.

Singular Extensions (SE)

This is the most important algorithmical addition in comparison with Ghost 2. It was a clear improvement to the search.
Although, I try to keep the engine as original as possible, my current implementation is inspired by ideas popularized by Stockfish.

All in all, the search is fairly minimal. It is still work in progress and hopefully we will see some improvements in the near future.
As a side note, Enhanced Transposition Cutoff (ETC) is no longer used. It tried hard to make it work but at best it was break-even and the code became more complicated.

Ghost 2:

MTD(f) search
Late move reduction (LMR) with verification search
(Many thanks to the authors of Fruit and Glaurung!)
Killer + history tables
Internal iterative deepening
Selective techniques like:
- Recursive nullmove ("2-3 plys reduction")
- Razoring + futility prunning
- History pruning
Enhanced Transposition Table Cutoff
Unique techniques:
- Perpetual check detection (much safer than in Ghost 1)
- Pin detection extension
- Local history counter (in contrast to global history counters)

Ghost 1:

Negascout search
Internal iterative deepening
Killer + history tables
Selective techniques like:
- Recursive nullmove ("3 plys reduction")
- Razoring + futility prunning
Prescan tables (never really worked well...)
Unique techniques:
- (Crazy) perpetual check detection (an unique, but too dangerous idea!)

Download:

Ghost 3.1 for Linux (64-bit version)
Ghost 3.1 for Linux (32-bit version)
Ghost 3.1 for Windows (64-bit version)
Ghost 2.0.2 for Linux (32-bit and 64-bit version)
Ghost 2.0.2 for Windows (32-bit and 64-bit version)
Ghost 1 for Linux (32-bit and 64-bit version)
Ghost 1 for Windows (only 32-bit version)

For Arch Linux based distributions, it is recommended to use the AUR package.

What about 32-bit Windows?

I know that there are requests for 32-bit Windows. Unfortunately, when I build a 32-bit binary of Ghost 3, it crashes immediately. If you would like to see a release of Ghost 3 for 32-bit Windows, please let us know.

Micro-Donation:

If you like Ghost, please flatter us:

Contact:

email addresses:
- Philipp Claßen philipp.classen [at] posteo.de, author of Ghost
- Michael Claßen michael.classen [at] gmx.net (concerning this website)

authors: Michael Claßen, Philipp Claßen

impressum

Last modified: Thu Oct 27 16:23:55 CET 2014