go-chess-minimax, v1.7

The library that implements a chess engine based on the minimax algorithm.

Improve the replacing strategy for same transpositions on storing in a transposition table.

calculate a move quality via searching terminators: move quality is directly proportional to a time of its evaluation;
in a transposition table:
- store moves qualities together with corresponding transpositions;
- replacing same transpositions on storing only if new one has a greater move quality.

move searcher used the negamax algorithm;
optimizations:
- alpha-beta pruning;
- transposition table:
  - storing transpositions in an LRU cache;
  - hashing a transposition by its representation in Forsyth–Edwards Notation;
  - replacing same transpositions on storing only if new one has a greater move quality:
    - move quality is directly proportional to a time of its evaluation;
  - sharing a transposition table between searches;
  - transposition table is safe for concurrent use (via a mutual exclusion lock over a whole storage);
- iterative deepening;
- parallel search (Lazy SMP):
  - launch concurrent searches with same depths;
searching termination:
- by a deep;
- by a time;
- by calling a special method (it's safe for concurrent use);
position evaluation only by a material (based on an evaluation function of Claude Shannon);
architecture features:
- easily extensible and composable architecture of searching;
- composable searching terminators.

Content: code.

License: MIT.