v1.5.1

• 🐛 Threefold repetition bugfix: Revert "Detect threefold repetition on pvNode (#796)" (#818)

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Full Changelog: v1.5.0...v1.5.1

v1.5.0

• 🔍 Add Futility pruning (FP) (#733)
• 🔍 LMR: allow when in check (#702)
• 🔍 LMR: reduce more if there's a TT move and a capture (#706)
• 🔍 Move RFP before NMP (#732)
• 🔍 SPSA search parameters tuning (#730, #764)
• ⚖️ Remove double pawns penalty [proper SPRT pawn eval] (#746)
• ⚖️ Index bishop mobility bonus by attacks count (#758)
• ⚖️ Index rook mobility bonus by attacks count exluding own pieces (#768)
• ⚖️ Add knight mobility bonus and index it by attacks count excluding own pieces (#775)
• ⚖️ Take only pawns into account for king shield (#789)
• ⚖️ Add king virtual mobility indexed by mobility count (#785)
• ⚖️ Use some Stoofvlees quiet data for eval tuning (#710)
• ⚡ Improve search logic (#725)
• ⚡ Use optimized method to check if a move was valid (#716)
• ⚡ Use a StringBuilder to generate UCI info command (#805)
• ⚡ Remove option to disable TT (#720)
• ⚡ Remove manual piece count during static eval (#698)
• ⚡ Simplify TaperedEvaluationTermByRank (#757)
• ⚡ Simplify TaperedEvaluationTermByCount (#767)
• ⚡ Simplify Aspiration windows (#802)
• 🐛 Fix index out of range exception on max depth (#708)
• 🐛 Detect threefold repetition on pvNode (#796)
• 🐛 Fix Game.MakeMove behavior on invalid moves (#804)

Non strength-winning changes:

• Add ponder support (#772)
• Generate UCI options for search parameters dynamically (#734)
• Normalize mobility values (#788)

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Full Changelog: v1.4.0...v1.5.0

v1.4.0

• 🔍 Improve RFP (#652)
• 🔍 Avoid doing TT cutoffs on PV nodes (#653)
• 🔍 Use TT score as positional eval for pruning (#692)
• ⚖ Tweak pawnless endgames evaluation (#693)
• ⌛ Tweak time management (#664, #665, #667, #668, #671, #677, #691)
• ⚡ Stop checking for two/threefold repetition and 50 moves draws in QSearch (#673)
• ⚡ Refactor Update50movesRule() method (#678)
• ⚡ Reimplement repetition detection (#679)
• ⚡ Prefetch TT entry in NegaMax search (#681)
• ⚡ Remove Position.StaticEval() heap allocations (#683)
• ⚡ Force GC collection at the end of Engine constructor and after ucinewgame (#685)
• ⚡ Use packed evaluation (#697)
• 🐛 Clear history on newgame (#649)
• 🐛 Fix long input position commands parsing (#650)
• 🐛 Fix engine stall when depth over 100 is reached during search (#651)
• 🐛 Don't search with fixed depth when cutechess provides 0s to move (#654)
• 🐛 Prevent illegal moves when low in time (#657)
• 🐛 Error when searching at max depth (#670)

Non strength-winning changes:

• Add fen UCI command (#688
• Increase max TT size from 1GB to 8GB (#669)
• 🐛 Fix behavior of consecutive go commands (#655)

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Full Changelog: v1.3.0...v1.4.0

v1.3.0

• 🔍 Add basic (quiet) history malus/penalty (#610)
• 🔍 Add capture history (#634)
• 🔍 Update (quiet) history moves only in beta cutoffs (#608)
• 🔍 Stop clearing quiet history (#637)
• 🔍 Take quiet history into consideration for LMR (#613)
• ⚡ Refactor move encoding methods and stop encoding special move flags individually (#622)
• ⚡ Store captured pieces as part of the move (#604)
• ⚡ Use jagged arrays ([][]) instead of multidimensional ones ([,]) (#605, #606, #607)
• ⚡ Simplify triple repetition detection logic, removing some branching (#623)
• ⚡ Make Piece an integer enum (#603)

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Full Changelog: v1.2.0...v1.3.0

v1.2.0

• 🔍 Prune SEE bad captures in QSearch (#558)
• 🔍 Reduce SEE bad captures in regular search (#564, #571)
• 🔍 Use spsa tuned search values (#543, #553)
• ⚖️ Add rook mobility to eval (#539)
• 🧬 Improve move generation: hardcode castling moves and a few calculated variables (#541)
• 🧬 Implement SEE and order bad captures after killers but before quiet moves (#554)
• ⚡ Reduce TT entry size to 8 bytes (#544)
• ⚡ Optimize go command parsing (#545)
• ⚡ Split MoveGenerator.GenerateAllMoves and MoveGenerator.GenerateCaptures to avoid branching (#549)
• ⚡ Set search thread as high priority (#546)
• ⚡ SEE micro-optimizations (#566)
• ⚡ Use stack-allocated span for movegen (#551, #596)
• ⚡ Optimize PositionHash (#582)
• ⚡ Optimize castling and en-passant moves Zobrist hashing (#577)
• ⚡ Replace EnPassantCaptureSquares dictionary with equivalent array (#578)
• ⚡ Optimize FEN parsing (#581)
• ⚡ Attempt to initialize MoveGenerator and GoCommand asap (#576)
• 🐛 Fix engine crash due to a negative calculated time to move (#555)
• 🐛 Add support for negative wtime and btime (#556)
• 🐛 Enable InvariantGlobalization and fix crash in some Linux scenarios (#575)

Non strength-winning changes:

• Add option to run bench at different depths (#537)

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Full Changelog: v1.1.0...v1.2.0

v1.1.0

• 🔍 Add Internal Iterative Reduction (IIR) (#507)
• 🔍 Add basic LMP (#512)
• 🔍 Improve TT replacement scheme: add required conditions for always replace (#526)
• 🔍 Add third killer move (#517, #525)
• 🔍 Use new history bonus formula based on Sirius and Berserk one (#527)
• 🔍 In case of 'fake' ponder-hit, research from depth 1 (#467)
• ⚖ Re-tune eval using some Stash data (#515)
• ⚡ Avoid PEXT array initialization when PEXT isn't supported (#516)

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Full Changelog: v1.0.1...v1.1.0

v1.0.1

Non strength-winning changes:

• 🐛 Clamp static evaluation within +- checkmate limits, preventing illegal moves (and erratic behavior in general) in positions with too much material on one side (#510).

  We're talking about positions here such as QQQQQQQQ/QQQQQQQQ/QQQQQQQQ/QQQQQQQQ/QQQQQQQQ/QQQQQQQQ/QPPPPPPP/K6k b - - 0 1, which will never happen in a real game but can be artificially set up (i.e. in lichess), so no strength change is expected in regular engine games.

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Full Changelog: v1.0.0...v1.0.1

v1.0.0

Getting out from ZeroVer club now that these two conditions are met:

• Lynx has basically reached feature-parity with BBC, engine outcome of BitBoard Chess Engine in C YouTube playlist that helped me the most during the initial phases of Lynx development.
• .NET 8 GA has been released and therefore Lynx no longer relies on pre-release SDK or library versions.

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• 🔍 Rewrite NMP (#479, #482, #492, #493, #494)
• 🔍 In case of 'ponder-hit', research last depth (#466)
• 🔍 Don't clear TT move if no best move is provided: keep old one II (#478)
• ⚖ Use PSQTs tuned without explicit piece values (#425)
• ⚡ Incremental move sorting (#477)
• ⚡ Avoid checking lack of material in static evaluation when the phase is high enough (#490)

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Full Changelog: v0.19.0...v1.0.0

v0.19.0

• 🔍 Tune LMR reduction (#452)
• 🔍 PVS-LMR logic improvement (#456)
• 🔍 Implement TT in quiescence search (#308)
• 🔍 Don't clear TT move if no best move is provided: keep old one (#462)
• ⌛ Check _searchCancellationTokenSource in qsearch as well (#454)
• 🐛 Avoid storing the same move duplicated in both killer moves (#458)
• 🐛 Ensure no search depth 0 happens after a 'ponder hit' (#465)

Non-strength winning chnages:

• 🐛 Fix ucinewgame command when followed by go command (#455)

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Full Changelog: v0.18.0...v0.19.0

v0.18.0

• ⚖ Tune PSQT (#414, #415, #417)
• 🔍 Add razoring (#429)
• 🔍 Add soft cap history moves score (#442)
• 🔍 Revisit and improve Aspiration Windows (#437)
• ⚡ Implement PEXT bitboards for bishop and rook attacks (#451)
• 🐛 Fix evaluation when checkmate is delivered at the same time 50 moves rule apply (#453)
• 🐛 Fix move ordering at high depths/LTC (#448, indirectly #442)
• 🐛 Avoid re-searches in IDDFS (#439)

Non-strength winning changes:

• ⚖ Normalize eval and add UCI_ShowWDL option (#421, #422)
• 🧹 Remove UseOnlineTablebaseInSearch from UCI (#441)

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Full Changelog: v0.17.0...v0.18.0