Chess engine: Astra 5.1 JA

Astra is a UCI chess engine written in C++.

Author: Semih Özalp

## Credits

- [Stockfish](https://github.com/official-stockfish/Stockfish)

- [Koivisto](https://github.com/Luecx/Koivisto)

- [Smallbrain](https://github.com/Disservin/Smallbrain)

- [Chess Programming Wiki](https://www.chessprogramming.org/Main_Page)

v.5.0:

NNUE Architecture

Previously 2x(768→1024)→1; now features a king bucket of size 10, resulting in a new arch: 2x(10x768→1024)→1

Evaluation

Besides the new network I added phase evaluation as well

Search

Improved time management within the search

Various other minor improvements

Miscellaneous

More efficient transposition table implementation

Added cuckoo tables to detect upcoming repetitions

Results vs. Astra 4.1

Astra-5 vs Astra-4.1 (STC)

Elo: 186.0 ± 7.3 (95%)

SPRT: 8.0+0.08s Threads=1 Hash=16MB

GAMES: N: 5474 W: 2984 L: 305 D: 2185

Astra 5.0 vs other engines:

Bitbit 1.3	8/8	+8	8 Games
Deep Blunder 1.2.0 JA	6/6	+6	6 Games
Aramis 1.4.0 JA	6/6	+6	6 Games
Schneckbert 1.0	5.5/6	+5	6 Games
Beef 0.3.6 JA	5.5/6	+5	6 Games
Demolito 2025-01-28	5/6	+4	6 Games
Yukari 2025.02.4 JA	5/6	+4	6 Games
Black Cat 2.5 JA	4.5/6	+3	6 Games
Odonata 1.0.0 JA	4.5/6	+3	6 Games
Perelandra 2.0	2.5/6	-1	6 Games
Berserk 20250203	1.5/6	-3	6 Games
SF-PRO2 05.02.2025	1/6	-4	6 Games
Colossus 2025a	4/4	+4	4 Games
Pioneer 0.3.2 JA	4/4	+4	4 Games
Mufasa 0.2.1 JA	4/4	+4	4 Games
Trinket 3.5.0 JA	4/4	+4	4 Games
Fatalii 0.9.0	4/4	+4	4 Games
Thrawn 2.1 JA	3.5/4	+3	4 Games
Midnight 9 JA	3/4	+2	4 Games
Peacekeeper 3.01 JA	2/4	+0	4 Games
Alexander 5.0	1.5/4	-1	4 Games

Jim Ablett compiles:

Astra 5.1 JA download