New version chess engine: Lynx 1.9.0 (Windows, MacOS, Linux)

Lynx it's written in C# (.NET 6). UCI protocol is needed.

Chess Engines Diary Rating CEDR=2890

Lynx release artifacts are self-contained and require no dependencies to be run.

However, you can also choose to build Lynx yourself.

Requirements

NET 6 SDK. You can find instructions about how to install it in yo

v.1.9.0

🔍 Search

Add PVS SEE pruning (#1521)

LMR: reduce more on TT capture when current move isn't (#1529)

LMR: reduce more on no TT PV (#1476)

LMR: deeper/shallower (#1535)

LMR: fractional w/ quantised base (#1514)

LMR: split base and history factor in quiet and noisy (#1512)

QSearch: don't use TT static eval (#1312)

QSearch: reuse TT score instead of TT static eval in QSearch when possible (#1319)

QSearch: don't do standing pat when in check (#1389)

Always predict cutnodes in ZWS with reduction, even if the reduction is 0 (#1304)

Extend on TT hit at low depths when TT cutoff doesn't happen but TT depth > depth (#1342)

Replace first legal move with BestMoveRoot() method when search depth 1 isn't completed (#1449)

Countermoves update: add pvNode || depth >= 3 condition (#1456)

IIR: on !ttHit -> on !ttHit || !ttMove (#1516)

Use final eval when available (checkmate, stalemate) as cached TT static eval (#1288)

SPSA (#1405, #1537)

⚖️ Evaluation

Pieces protected by pawns -> bucketed array, indexed by piece (#1324, #1336)

Passed pawns -> opponent buckets to passed pawns bucketed arrays (#1349)

Bishop major threats (#1415, #1420)

Bishop in non-blocked long diagonal (#1439)

Pawn islands (#1431)

Connected rooks (#1436)

Incremental static evaluation for PSQTs (#1350, #1353)

Pawn structure eval table (#1365)

Incremental phase (#1412)

⚡Speedups

Split ScoreMove between regular search and qsearch (#1410)

Remove Engine.StopSearching and Engine_stopRequested (#1296)

Use in readonly struct when passing args, when possible (#1462)

Precalculated pawn islands (#1440)

Remove passed pawns double array (#1491)

Add inline hints to TTElement getters (#1513)

Use explicit SEE.IsGoodCapture() method when we know it's a capture (#1528)

Replace GetLS1BIndex() + ResetLS1B() loop calls with a WithoutLS1B() method that 'outs' the index (#1536)

⌛ Time management

Don't search for shorter mates when low on time (#1398)

🟰 Multithreaded search

Replace Task.WhenAll with Task.WhenEach, processing faster results from extra threads (#1545)

🐛 Bugfixes

Engine doesn't becomes unresponsible any more when number of Threads gets close or over the logical cores of the machine (#1292)

Fix crash when multithreading and pondering when GUI doesn't wait for bestmove after a stop (#1394)

Fix cutechess warnings when pondering by avoiding single-move early returns while pondering (#1395)

Use TT recalculated scores everywhere and move TT cutoffs to NegaMax and QSearch methods (#1310)

Distinguish side on initial Zobrist key calculation (#1363)

Ensure that hashfull calculation doesn't fail if TT < 1k items (even if not currently possible) (#1393)

Non-strength winning changes

Make engine <-> GUI time overhead configurable (via EngineGuiCommunicationTimeOverhead) (#1442)

Refuse to parse FENs without (or with more than) one white and one black king (#1351)

Don't stop when a short-enough mate is found, continue trying to find a faster one (#1287)

Make single move score more recognizable (#1461)

Replace first legal move with BestMoveRoot() method when search depth 1 isn't completed (#1449)

Plan for whenever ChessGUI wakes up feeling like sending negative movestogo (#1519)

Lynx 1.7.0 vs other engines:

Berserk 12	0/8	-8	8 Games
Seer 2.7.0	0/8	-8	8 Games
Pingu 2.0.0	1/6	-4	6 Games
Stockfish 15.1	0.5/6	-5	6 Games
Mida 2.2	0.5/6	-5	6 Games
Boychesser 1.0	0.5/6	-5	6 Games
Brainlearn 26.1	0/6	-6	6 Games
Hazard 3.78	0/6	-6	6 Games
ShashChess 34.1	0/6	-6	6 Games
Vafra 12.5 Cfish	0/6	-6	6 Games
Obsidian 6.0	0/6	-6	6 Games
Polyfish 231022	0/6	-6	6 Games
Pawn 2.0	0/6	-6	6 Games
CorChess 20231024	0/6	-6	6 Games
Raid 2.78i_X	0/6	-6	6 Games
Tofiks 1.3.0	4/4	+4	4 Games
Alpaca 0.2.5	4/4	+4	4 Games
Lux 3.4	1/4	-2	4 Games
RukChess 3.0.16	0.5/4	-3	4 Games
Sirius 5.0	0.5/4	-3	4 Games
Akimbo 0.7.0	0/4	-4	4 Games

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Lynx 1.9.0 download 

github:https://github.com/lynx-chess/Lynx/releases/