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Released October 15, 2012.
Houdini 3 contains many evaluation and search improvements in all phases of the game and is about 50 Elo stronger than its predecessor Houdini 2 (which at the time of writing was still unmatched by any other engine). The opening improvements relate mostly to piece mobility and space management and are most convincingly demonstrated by the progress in Fischer Random Chess for which Houdini 3 has become about 75 Elo stronger. In the middle game Houdini 3 has significant enhancements for recognizing pieces with limited mobility and in king-side safety. Houdini 3 will seek deeper in end games and solve more positions than before.
In the new Tactical Mode Houdini 3 will prefer tactical instead of positional solutions. In tactical test suites the Tactical Mode will find more solutions and provide significantly faster solution times, often by a factor of 3 to 10.
The Accelerated Principal Variation Search or “Smart Fail-High” is especially useful in very deep analysis when a different move becomes best at very high search depth. Houdini 3 will apply an automatic depth reduction that often speeds up finding the Principal Variation by a factor of 5 to 10.
Besides Nalimov and Gaviota End Game Table Bases, Houdini 3 now also supports Scorpio bitbases. These bitbases are loaded in memory when the program starts (requiring about 300 MB of memory) and are then readily available to the engine.
Hash usage has been optimized, improving back-tracking analysis. Houdini 3 Pro will now support hash tables up to 256 GB.
The engine evaluations have been carefully recalibrated so that +1.00 pawn advantage gives a 80% chance of winning the game against an equal opponent at blitz time control. At +2.00 the engine will win 95% of the time, and at +3.00 about 99% of the time. If the advantage is +0.50, expect to win nearly 50% of the time.
Fun fact: Over 10 million chess games were played for the development and tuning of Houdini 3!
Released November 20, 2011.
Improvements and New Features
Released October 7, 2011.
Improvements and New Features
Released September 1, 2011.
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.
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.
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 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.