Lambergar v0.5.2

Release Notes

• This release brings some minor bug fixes.
• UCI interface has been reorganized and is now smaller in terms of code size, but has same functionality.
• Some code refactoring so that the project can be compiled with newer zig versions. However, zig versions newer than 0.12.0-dev.1536+6b9f7e26c make engine really slow.
• Improved time controls.
• Strength of the engine remains the same as in version v0.5.1.

Lambergar v0.5.1

Release Notes

This release brings several bug fixes, with the major one addressing a flaw in the calculation formula for determining the new history value. The previous formula did not limit the history value, leading to an integer overflow issue at certain points, resulting in negative values. Consequently, during move sorting, the best quiet moves were erroneously placed last. This issue was more pronounced during longer time controls, where there were more opportunities to increase the history value. At lower time controls (up to 10 seconds per move), the new formula may actually reduce the engine's strength by 10-20 ELO points. However, at longer time controls, version v0.5.1 demonstrates improvement in engine strength over the previous version. At approximately 1 minute per move, the new version is approximately 50 ELO points stronger, with even more significant gains observed at longer time controls.

Lambergar v0.5.0

Builds

Currently there are two basic builds: vintage and popcnt. The vintage version is for really old computers, while popcnt is for modern computers.

Main Features

• Improved evaluation function: Now includes tuned:
  • Piece values
  • PSQT (Positional Square Table)
  • Pawn evaluation:
    • Passers
    • Isolated pawns
    • Blocked pawns
    • Supported pawns
    • Evaluation of pawn phalanx
  • Piece mobility
  • Piece attacking evaluation
  • Basic king safety
• Some minor improvements: Search function, history heuristics, and move sorting
• Time controls: improved time controls

Lambergar v0.4.1

Release Notes

This release includes two bug fixes:

1. Excessive Memory Usage: We resolved an issue with excessive memory usage. The problem originated from the use of an incorrect memory allocator. Previously, we used the Arena memory allocator, which, according to a discussion on Ziggit, does not release memory. We have now switched to using the c_allocator directly.

2. Engine Unresponsiveness: We fixed an issue where the engine would get stuck in search mode and not respond to commands from the interface. This was due to the use of a single thread, and interfacing was only possible once the search had finished. We have now resolved this by using a separate thread for the search routine. This improvement also lays the groundwork for implementing a multi-threaded search in the future.

Please note that these changes do not improve the engine's strength.

Lambergar v0.4.0

Builds

Currently there are two basic build: vintage and popcnt. Vintage version is for really old computers, popcnt is for modern computers.

Main features

• New evaluation parameters
• Tuner for evaluation parameters
• Changed history heuristics and move sorting
• Improved apiration window algorithm
• Changes in prunings and reductions
• I have been changing and massaging the code quite a bit, so I lost the track of all the changes, but the improvements are quite substantial

Time controls 30s+0.5s

Score of Lambergar vs Lamb031: 706 - 67 - 207  [0.826] 980
...      Lambergar playing White: 379 - 21 - 91  [0.865] 491
...      Lambergar playing Black: 327 - 46 - 116  [0.787] 489
...      White vs Black: 425 - 348 - 207  [0.539] 980
Elo difference: 270.6 +/- 22.9, LOS: 100.0 %, DrawRatio: 21.1 %

v0.3.1c

• release with different x86-64 microarchitecture levels

• x86-64 is baseline microarchitecture

• x86-64-v2 supports vector instructions up to Streaming SIMD Extensions 4.2 (SSE4.2) and Supplemental Streaming SIMD Extensions 3 (SSSE3), the POPCNT instruction.

• x86-64-v3 adds vector instructions up to AVX2, MOVBE, and additional bit-manipulation instructions.

• x86-64-v4 includes vector instructions from some of the AVX-512 variants.

(source: https://developers.redhat.com/blog/2021/01/05/building-red-hat-enterprise-linux-9-for-the-x86-64-v2-microarchitecture-level#background_of_the_x86_64_microarchitecture_levels)

v0.3.1b

• Fixed issues with UCI commands requiring space after command to work on Windows.
• Compiled for two Intel architectures

Lambergar v0.3.1

This is the first public release of Lambergar chess engine.