Chess Engines Diary

Blunder - UCI chess engine Author: Frederic Marchais Blunder  is a brand-new engine that the Chess Engines Diary team hasn’t tested yet. Two earlier engines with the same name were created by Christian Dean and Jan Frase . The first test results will be out soon, so keep an eye on our website for updates. Blunder 0.7.0 what's new?  Skill system, UCI fixes, time management, bench tooling Features: - Skill UCI option (1-20) with eval noise for weakened play - UCI_LimitStrength / UCI_Elo options with linear Elo-to-skill mapping - Book usage scales with skill level - Coach commands always run at full strength Bug fixes: - UCI bestmove 0000 under fast-chess (race condition + multipv override) - Time management: set abort flag when hard limit exceeded (~900 Elo gain) - NPS reporting in test_positions() Bench tooling: - bench elo: binary search for absolute Elo vs Stockfish - fast-chess 1.8 compatibility (pgnout, args, parser) - Streaming output for kiro-monitor hang detection ...

Blunder - UCI chess engine Author: Frederic Marchais Blunder 0.3.8 is a brand-new engine that the Chess Engines Diary team hasn’t tested yet. Two earlier engines with the same name were created by Christian Dean and Jan Frase . The first test results will be out soon, so keep an eye on our website for updates. Blunder 0.3.8 download

  Blunder - chess engine, first (mostly) UCI conform playable version! Author: Jan Frase An attempt to build a chess engine from scratch. Built with Java Blunder 2025-08-14 download

Blunder - UCI chess engine Author: Christian Dean, Rating CEDR= 2611 v.8.5.5 Blunder 8.5.5 includes several new features, as well as some strength gaining tweaks to the engine. Singular extensions have been added, as well as bishop outposts. The time management has been tweaked to be a bit stronger, as well as late-move reductions. Bugs where the fifty-move rule wasn't reset for a capture and checkmate didn't trump the fifty-move rule have been corrected, as well as a bug in the transposition table replacement scheme. This version of Blunder should be ~40-50 Elo stronger than 8.0.0 at bullet time controls. Blunder 8.5.5 download Individual statistics:  Blunder 7.6 - 60 games CEDR (+ 42,=  6,- 12), 75.0 % Jinx 1.0                      :   4 (+  4,=  0,-  0), 100.0 % NoC 4.20                      :   4 (+  1,=  2,-  1), ...

Blunder - UCI chess engine Author: Christian Dean, Rating CEDR= 2569 v.8.0.0 This release is very similar in spirit to that of 5.0.0, in the sense that much of the work done has been improvement and optimization of the code base through slow, large-scale refactoring, which has brought about Elo gains, although several new strength-gaining features have been implemented. Blunder 8.0.0 is estimated to be about 50 Elo stronger than 7.6.0 at bullet time controls. It'd be impossible to list every last change, but a summary of some of the major areas will be listed below. Improvements to Blunder's move generator have been made, improving it's speed by 10-15%. Thanks in particular to Koivisto, for giving me the idea to store the hash of a position  as part of it's irreversible state, leading to a nice speed increase. Small tweaks have been made to the UCI that's made it a bit more user friendly and hopefully more straightforward to use. Magic bitboard generation code and ...

Author: Christian Dean Blunder 7.6.0 for Android download

Blunder - UCI chess engine Author: Christian Dean, Rating CEDR= 2985 (75 place) v.7.6.0 This release contains no new features, but various tweaks of existing ones that have improved Blunder's strength. History values are decreased when the move fails to raise alpha or cause a beta-cutoff, queen promotions are considered in quiescence search, pawn pushes to the 6th rank and above are no longer reduced, and late-move reductions are no longer allowed to drop the search directly into quiescence search. These changes are summarized below and resulted in a gain of around 80 Elo in self-play. Blunder 7.6.0 download

Blunder - UCI chess engine Author: Christian Dean, Rating CEDR= 2807 (60 place) v.7.5.0 The release of Blunder 7.5.0 consists of mostly strength gaining tweaks to Blunder's previous features, with the exception of the addition of late-move pruning/move-count based pruning. This version is estimated to be roughly 30 Elo stronger than Blunder 7.4.0. Blunder 7.5.0 download

Blunder - UCI chess engine Author: Christian Dean, Rating CEDR= 2807 (60 place) v.7.4.0 The release of this version includes evaluation terms for passed pawns and knight outposts, a new form of dynamic time management, and a better tuned evaluation, particularly with regards to king safety. All of these additions amount to about 50 Elo in gauntlet testing over 7.3.0, and self-play tests show Blunder 7.4.0 is roughly 50 Elo stronger than 7.3.0 (tc=inf/10+0.1): Blunder 7.4.0 download

Blunder - UCI chess engine Author: Christian Dean, Rating CEDR= 2807 (60 place) v.7.3.0 New features included in this version are evaluation terms for king safety and pawn structure. Both are still quite basic and have much lacking, but I believe them to be solid designs to build on in future versions. Addtionally, all evaluation terms have been retuned on a larger dataset, yielding some minior gains. However, most of the strength gain in this new version comes from slight tweaks to the pruning parameters and conditions for late-move reductions, null-move pruning, and futility pruning. Lastly, there are some non-strength gaining tweaks here and there, code clean-ups, and the command line interface is much more user friendly. The major changes as usual are summarized below: Engine Improved command-line interface UCI command movetime now implemented Search Tweaked futility pruning's allowed depth and margins Tweaked the formula for calculating null-move reductions (much more agressi...

Blunder - UCI chess engine Author: Christian Dean, Rating CEDR= 2533 v.7.2.0 This release is not a notable strength improvement over 7.1.0. However, 7.2.0 does introduce a polyglot opening book loader as the primary new feature. Several UCI options are provided to make usage of the loader. Additionally, various places in the codebase have been refactored and cleaned-up, and the evaluation for Blunder has been retuned and restructured to allow for more granularity. Lastly, a makefile is now included so Blunder can be more easily compiled across platforms. Engine Polyglot opening book loader Evaluation Refactored & retuned Blunder 7.2.0 download

Blunder - UCI chess engine Author: Christian Dean, Rating CEDR= 2533 v.7.1.0 The release of this version includes late-move reductions, basic futility pruning, as well as a static-exchange evaluation routine, as well as a little refractoring and bug-fixing here and there. The Elo gains for each feature can be seen in the commit history. Going forward this will be the place where I try to document Elo gains (if any) from new features. Blunder 7.1.0 download

Blunder - UCI chess engine Author: Christian Dean, Rating CEDR= 2533 v.7.0.0 These additions show 7.0.0 is a little more than 100 Elo stronger than Blunder 6.0.0 (6.1.0 is not discussed here as it is a slight, but more stable regression from 6.0.0's strength) in self-play, and combined with gauntlet testing, gives a strength estimate of 2250-2350 Elo. Blunder 7.0.0 download

Blunder - UCI chess engine Author: Christian Dean, Rating CEDR= 2533 Blunder 6.1.0 download

Author: Christian Dean Blunder 6.0.0 for Android download

From the author:  v. 6.0.0   Blunder 6.0.0 includes an implementation of reverse futility pruning and history heuristics, both which from self-play contributed 80-100 Elo. Additionally, the UCI stop command has been implemented, as well as some general code cleanups. Blunder 6.0.0's estimated rating is ~2100-2150 Elo. Author: Christian Dean Blunder 6.0.0 download

From the author:  Blunder 5.0.0 is a complete rewrite of the engine. Many basic design ideas and principles were kept, and some areas were just ported over, but the majority of the code-base was rewritten, and the layout of the project was completely changed. The motivations behind this rewrite were twofold: First, I was dissatisfied with Blunder's speed and wanted to take another crack at creating an engine that was simply faster. Second, I didn't like how Blunder was designed in several places, and I quickly realized these "several places" constitued large chunks of the code-base. So Blunder 5.0.0 was the result. From the testing I've done, Blunder 5.0.0 is 20-30% faster than Blunder 4.0.0, and perft(6) from the starting position was coming in at around 6-8s (14-18 Mnps), whereas perft(6) from the starting position for Blunder 4.0.0 was generally 10-12s (10-12Mnps). And overall, I'm happy with the refractoring I've done and my code feels cleaner in many...