LittleThought: Chess Engine

Stay up to date!

Back to main LittleThought page.

Change History

LittleThought v1.052 (22/04/2010)

Fixed the last Chess960 bug!

LittleThought v1.051 (21/04/2010)

Fixed several Chess960 bugs
Fixed display of illegal move error msg

LittleThought v1.05 (20/04/2010)

Added Chess960 support
Re-implementation of multithreading, now uses YBWC and can use up to 8 threads
Extensive retesting of all eval features and removed several misbehaving features
Improved time management - can handle sub-second games and better able to extend/reduce time on searches
Added divide command
Fixed problem with using opening book
Fixed crash with extremely long games
Fixed a time control initialisation bug when switching between modes without restarting

LittleThought v1.04 (07/11/2009)

Fixed illegal move bug encountered when playing long games (> 200 moves)
Fixed bug with false single reply extensions being triggered
Several performance enhancements throughout the code (~15-20% faster)
Some endgame evaluation improvements
Several improvements to the search reductions
Better time management at very fast controls
Rename UseBook to OwnBook as per UCI standard
Fixed 64-bit compile options so the 64-bit program is significantly faster than the 32-bit one

LittleThought v1.03 (04/01/2008)

Rewrote move scoring algorithms
Modified reductions/pruning
Modified lazy eval settings
Some debug logging enhancements
Fixed hash write bug
Fixed several SMP issues

LittleThought v1.02 (07/11/2007)

Fixed bug in q search
Fixed bug in lazy eval
Complete redesign of node recognisers and vastly improved specialised endgame knowledge

LittleThought v1.01 (25/07/2007)

Fixed SMP bugs (repetition, check extensions, root ordering)
Fixed hash indexing bug and tweaked memory utilisation
Fixed bug with mobility eval (was getting used randomly!) and improved it
Fixed bug in endgame recogniser
Fixed bug in 50 move draw check
Prevent LMR of killer moves
Added 50-move rule to internal node draw recognition
Improved single reply extensions
Tweaked extensions/reductions
Some performance improvements
Lots of eval fine tuning of values
Enhanced interior node evaluation

LittleThought v1.00 (03/02/2007)

Bug fixes include:

Fixed eval problem with 50 move rule
Fixed bugs in move generator (was searching duplicate moves and skipping some legal moves)
Fixed bug in move scoring
Fixed bug in handling of "position fen" commands used to analyze games
Fixed issue with recogniton of special endgame positions
Fixed bugs with rook eval
Fixed randomisation bug with book
Fixed issue with single reply extensions
Fixed UCI move number display
Fixed calculation of next ply estimated time
Fixed UCI lower/upper bound score output
Fixed horrendous hash bug
Fixed bug in PVS re-search
Fixed go depth command
Fixed repetition detector (and improved performance)
Fixed storing of mate scores in hash
Fixed pawn hashing bug
Added EP capture into check evasion move generator!

Improvements made:

Added eval cache (UCI param EvalHash default 16MB)
Improved pawn + bishop eval
Improved recapture extensions
Moved more eval into lazy eval section
Tweaked null move criteria
Added null move verification search
More endgame recognisers
Added penalties for losing castling rights
Added simple candidate passed pawn eval
Added connected passed pawns bonus
Reduced value of passed rook-pawns
Implemented fractional extensions and tweaked extension settings
Added passed pawn extensions
Tweaks to q search cutoff criteria
Improved passed pawn eval with queens
Tweaked Knight's piece square table
Improved KRvK strategy
Reduced underpromotion moves
Added knight outpost eval
Tweaked futility pruning criteria
Improved mobility eval
Tweaked LMR settings
Tweaked aspiration search
Tweaked recapture extensions
Added mate distance pruning
Special root move ordering
Rewrote hash replacement scheme and probing
Tweaked check extensions
Tweaks to time management
LOTS of performance enhancements

Other:

Removed 15 sec buffer from time controls used to workaround Polyglot issue with new cygwin dll (can re-enable it via new TimeBuffer parameter)
Reduced default pawn hash table to 1024KB and changed UCI parameter from MB to KB
Added support for go nodes xxx
Added more debug level output (tracelevel=2) to show all root move scores
Reduced volume of UCI info at shallow depths
Improved EPD file parsing for running test suites

LittleThought v0.98 (12/11/2006)

Fixed stupid board drawing issue (when in console mode, not UCI)
Fixed several move generator bugs
Fixed incredibly stupid hash bug
Redesigned hash table for more efficient usage
Improved eval for knights
Added extended futility pruning
Replaced Verbose uci option with TraceLevel which allows various levels of debugging output

LittleThought v0.971 (08/11/2006)

Improved eval for knights
Fixed bug in eval for rooks
Added some additional knowledge to the eval for rooks and queens
Cleaned up some debugging code

LittleThought v0.97 (22/10/2006)

Fixed several hanging and timing issues with Polyglot from v0.95 (yaay!)
Fixed nasty bug in move generator from v0.94
Disabled misbehaving mate threat extensions from v0.93
Modified Q search to avoid some types of horizon problems
Added single reply extension
Improved trans table aging method

LittleThought v0.96 (20/08/2006)

Added UCI option logstats more for my benefit than anyone else's, but maybe other engine authors will find it usefull
Finally added some king safety eval
Modified null move pruning logic
Disabled I/O buffering to try and fix some Polyglot timing issues

LittleThought v0.95 (20/08/2006)

PV Split parallel search implemented - up to 4 searcher threads supported (not much better than 2 though)
Cleaned up code alot to help in transition to SMP search and uncovered several bugs
Sends more regular and complete UCI stats
Some decent performance improvements (up to 30%)
Fixed bug in LMR and futility pruning criteria
Fixed several hashing bugs
Fixed time control bug
Fixed a bug with the boolean UCI parameters
Tweaks to aspiration search
Tweaks to time control usage
Removed some useless SSE2 code so it now works on older CPUs

LittleThought v0.94 (23/07/2006)

Compiled 64-bit version (about 1.5x faster!)
Resized pawn hash entries for less memory usage
New opening book format to use less memory
Performance optimisations
Fixed futility pruning
Move ordering improvements
Initial changes to support multithreading
Added recogniser for KBNvK end games

LittleThought v0.93 (11/07/2006)

Added end game score modifiers for some probable drawn positions
Added extra pawn end game knowledge (some KPvK stuff)
Fixed flush problem under Fritz GUI
Added skill level modification option (NumBeers)
Fixed UCI hash configuration problem
Improved futility pruning
Improved Q search
Fixed bugs in end game eval, pawn eval, king safety eval
Several performance optimisations
Added null move threat extensions
Modified move scoring

LittleThought v0.92 (15/06/2006)

Removed Winboard support, UCI only now (too much overhead supporting two interfaces!)
Added recapture extensions
Fixed static eval symmetry bugs
Added some simple mobility scoring to static eval
Improved killer move handling
Improved LMR criteria

LittleThought v0.91 05/06/2006

Fixed intermittent crashing bug

LittleThought v0.90 03/06/2006

Fixed problem causing LT to lose on time in certain scenarios

LittleThought v0.89 01/06/2006

Fixed null move bug
Improved Q search move ordering
Enhancements to pruning/reductions/extensions
Additional XBoard protocol support
Removed support for non-PVS searches

LittleThought v0.88 21/05/2006

Enhanced UCI info
Fixed Q Search bug (caused false mate reporting among other things)
Improved move generator for check evasions (and fixed a few bugs!)
Fixed unstoppable pawn detection
Improved end game knowledge and draw recognisers
Slight improvement in move ordering with IID
Misc eval improvements (king safety, bishops, tropism)
Fixed bug with UCI position setup (position fen command)
Improved Q search move ordering

LittleThought v0.87 15/05/2006

Completely rewrote move generator/make move to allow for improved move ordering/performance
Created very simple (and dumb) opening book (and created new option usebook)
Added futility pruning

LittleThought v0.86 07/05/2006

Fixed null moves (yaaaay) and re-enabled them by default
Improved some end game eval
Fixed issue with mate scores (for real this time!)

LittleThought v0.85 06/05/2006

Added pondering
Added go infinite and stop commands (allow analysis until told to stop)
Sends hash full % UCI info
Added verbose option (default false) to disable info string commands

LittleThought v0.84 05/05/2006

Improved time control (may extend time if almost finished a ply on timeout, moves quick if only a single legal move)
Fixed yet another nasty move generator bug (how on earth did old versions ever win a game?)
Fixed issue with storing mate scores in hash table incorrectly

LittleThought v0.83 01/05/2006

Fixed some king safety eval
Added additional Winboard commands: time, otime
Fixed and re-enabled pawn hash, plus some other performance improvements means it is ~50% higher nps now!
Improved pawn eval

LittleThought v0.82 30/04/2006

Fixed bug in move generator causing some moves to be skipped!

LittleThought v0.81 29/04/2006

Fixed problems with setoption command (was not using advanced search algos)
Fixed problem with MTD(f) search
Changed default search to PVS
Tidied some UCI info output
Fixed draw by repetition bug causing it to lose instead of draw
Improved null move logic (?)
Some additional eval logic (recognise insufficient material, improved pawns)
Fixed bugs in Q search
Fixed move generator bug (invalid killer moves)
Fixed bugs with null move and hash tables
Fixed bug with move ordering
Fixed some small memory leaks
Fixed bug in history scoring

LittleThought v0.80 23/04/2006

First released version for ChessWar IX and WBEC Qualifying