Hydra 1.1.0 - new version chess engine

Hydra - UCI-compatible chess engine written in pure Python — no C extensions, no numpy, no external dependencies.
Estimated strength: ~2000 Elo (Stockfish UCI_Elo calibration, 100 ms/move).

Author: Miloslav Macůrek

Hydra 1.1.0 what's new?

This release is focused entirely on performance. No new features, no new search algorithms — just making the existing engine significantly faster, which directly translates to stronger play.

Estimated strength: ~2000 ELO

What changed

Evaluation cache — static eval is now cached by Zobrist hash (up to 65 536 entries), avoiding redundant recomputation for positions seen multiple times during search

Pawn structure cache enlarged from 4 096 → 32 768 entries

Removed hanging-pieces detection from static evaluation — SEE (Static Exchange Evaluation) already handles tactical compensation in search, making the static penalty redundant and expensive

Conditional SEE skip — captures where the victim is worth more than the attacker are ordered directly via MVV-LVA, saving a full SEE call per move in most exchanges

Faster LSB extraction in move generation — replaced De Bruijn multiplication + table lookup with (bb & -bb).bit_length() - 1, leveraging CPython's native integer representation (~21% faster per call, 82 call sites updated)

History-malus micro-optimisations — destination square hoisted out of inner loop, set-literal allocations eliminated.

Hydra 1.1.0 - download from page