Welcome to the Houdini Chess Engine home page. Houdini is a state-of-the-art chess engine for Windows combining outstanding positional evaluation with the most sophisticated search algorithm.

The name Houdini was chosen because of the engine's positional style, its tenacity in difficult positions and its ability to defend stubbornly and escape with a draw – sometimes by the narrowest of margins. On the other hand Houdini will often use razor-sharp tactics to deny its opponents escape routes when it has the better position.

At the time of writing Houdini leads all the major Computer Chess rating lists and is widely considered to be the strongest chess engine on the planet. From numerous interviews it appears that many top Grand Masters including the current chess World Champion Viswanathan Anand use and appreciate Houdini.

The Chess Club Live Facebook page phrased it like this: "If there ever was a computer descendant of the romantic players like Morphy, Anderssen, Spielmann, Marshall, Bogojulbow, Tal, Nezhmetdinov, Shirov, Morozevich it would be Houdini. Houdini is the current World number 1 chess engine and plays in a very romantic style."

Follow the development of the Houdini Chess Engine on Facebook:

Houdini 2 is now available!

News Flash: The update Houdini 2.0c has now been released, see the list of changes!

The new Houdini 2 focuses on enhancing the user experience and analysis capabilities of the engine, while providing a useful improvement in strength.

Click here to see a list of new features and improvements in Houdini 2. Full details about installation and configuration of the engine are available in the on-line Houdini Chess Engine User's Guide.

Improved Analysis support: Save Hash to File, Load Hash from File, Never Clear Hash

The complete hash table can be saved to a disk file and reloaded later for continuing the analysis.

Houdini 2 makes better use of the data in the hash table to restart instantly the analysis at the point where it was previously interrupted.

By saving the hash table in a disk file you can interrupt the analysis anytime. At a later date you can reload the hash table file in memory to continue the analysis as if no interruption had happened.

The new "Never Clear Hash" option will keep the hash data in memory even when the position changes or when starting a new game.

Position Learning

The "Position Learning" mode will automatically save analysis results in a learning database that will be reused in future analysis. This is a more convenient, but less powerful method of using previous analysis results than the manual Save Hash/Load Hash operations of the previous point.

Strength Limit feature

Houdini 2 can limit its skill level from 0 (beginner) to 100 (full strength).

The strength is limited through a combination of techniques: limiting the number of positions searched, purposely picking a non-optimal move, and ignoring table bases.

Up to what skill level can you beat Houdini?

Chess960 (Fischer Random Chess) Support

Houdini 2 supports Chess960 a.k.a. Fischer Random Chess games.

Mate Search

To speed up solving deep mates, you can fix a limit on the search depth during the mate search.

Houdini Pro version for high-end users with powerful hardware

For advanced servers with many cores on multiple sockets (usually with so-called NUMA architecture), a special Houdini Pro version is available. It significantly improves the scaling of Houdini up to 32 cores and makes use of up to 32 GB of hash memory.

Improved strength

Improved evaluation and search make Houdini 2 Standard about 25 Elo stronger than its predecessor Houdini 1.5a. On high-end hardware Houdini 2 Pro with its additional NUMA-related speed improvements is about 40 Elo stronger than Houdini 1.5ab-16.

Houdini 2 Versions for Windows

Houdini is written for Windows and will run on any not too ancient Windows version. On Linux you can run Houdini using Wine without any significant performance loss.

Two Houdini 2 versions are available:

Houdini 2 Standard €39.95 +VAT Best buy for most users with main-stream hardware. Supports up to 6 cores and 4 GB of hash. Houdini 2 Pro €59.95 +VAT For high-end users with powerful hardware. Supports up to 32 cores and 32 GB of hash and NUMA-architecture. Click here for more information about Houdini Pro.

Purchasing Houdini 2 will entitle you to all updates and corrections made to Houdini 2, direct e-mail support by the Houdini author and discounts to future versions of Houdini.

The Houdini 2 download link and serial number will be sent to you by e-mail within 24 hours of purchase. If you haven't received the confirmation mail within that time frame, check your spam folder first, and if the mail is not there please contact us immediately via the support e-mail address houdini@cruxis.be.

Too expensive? You can still download the free Houdini 1.5 which at the time of the Houdini 2 release remains unmatched in strength by any other chess engine.

Support

Direct support by the author of Houdini, Robert Houdart, is available by e-mail at the address houdini@cruxis.be.

Before mailing please check out the on-line Houdini Chess Engine User's Guide with installation tips and Frequently Asked Questions.
If for whatever reason e-mail communication fails, you can contact us on Facebook .

Version history

Houdini 2

• Houdini 2.0c (20111120): Maintenance update with minor bug corrections and new analysis options.
• Houdini 2.0b (20111007): Maintenance update with minor bug corrections and Nalimov EGTB support.
• Houdini 2.00 (20110901): Improved analysis capabilities, enhanced search and evaluation.

Houdini 1.5

• Houdini 1.5a (20110115): Maintenance update with work-arounds for Fritz GUI and other minor improvements.
• Houdini 1.50 (20101215): Improved search and evaluation. Gaviota Table Base Support.

Houdini 1.0

• Houdini 1.03a (20100717): Bug fix for Multi-PV.
• Houdini 1.03 (20100715): Multi-PV, searchmove and large page support. Improved evaluation function.
• Houdini 1.02 (20100618): SMP and hash collision bug fixes. Work-around for Shredder GUI.
• Houdini 1.01 (20100601): Bug fixes. Improved search algorithm.
• Houdini 1.00 (20100515): First release.

Acknowledgements

An invaluable resource for any chess engine author is the excellent Chess Programming Wiki.

Without many ideas and techniques from the open source chess engines Ippolit and Stockfish, Houdini would not nearly be as strong as it is now.

The Gaviota EGTB probing code used by Houdini is © Miguel A. Ballicora.