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Bread 2.0.0

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@Nonlinear2 Nonlinear2 released this 18 Oct 22:56
· 261 commits to main since this release
v2.0.0
3f254a2

Thanks to a new neural network and many search improvements, Bread 2.0.0 is much stronger than version 1.6.0!

Short time control (8 + 0.08 s) +382 Elo
Long time control (40 + 0.4 s) +340 Elo

NNUE

Bread's neural network has been mostly rewritten. It was retrained from zero knowledge on 40 million games of self play, making Bread a "zero" engine.

More precisely, improvements include:

  • a modified architecture: 768x2 -> 1024x2 -> 1, trained on ~5 billion positions with 10 self play training iterations (~369 elo)
  • screlu activation for the feature transformer (~21 elo)
  • output buckets (~5 elo)
  • direct accumulator calculation (~30 elo)
  • a sped up L1 inference (~8 elo)

Main search:

  • use tt_capture for nmp reductions (~7 elo)
  • add continuation history pruning (~15 elo)
  • two SPSA tunes (~48 elo)

General improvements:

  • add support for the genfens command
  • fixed makefile executable extension for linux
  • improve threefold detection (~22 elo)

Improved Nonsense option

Bread features a uci option called Nonsense, which has been improved in this release. If the option is active, bread will:

  • play the bongcloud opening
  • print lyrics from "never gonna give you up" during search
  • take all of the opponent's pieces and promote all pawns to knights and bishops

Progression tests results

STC: 8 + 0.08 s

Results of bread_engine_2.0.0 vs bread_engine_1.6.0 (8+0.08, 1t, 16MB, UHO_2024_8mvs_big_+115_+134.pgn):
Elo: 382.18 +/- 19.10, nElo: 618.97 +/- 15.23
LOS: 100.00 %, DrawRatio: 7.60 %, PairsRatio: 461.00
Games: 2000, Wins: 1666, Losses: 65, Draws: 269, Points: 1800.5 (90.03 %)
Ptnml(0-2): [0, 2, 76, 241, 681], WL/DD Ratio: 4.85

LTC: 40 + 0.4 s

Results of bread_engine_2.0.0 vs bread_engine_1.6.0 (40+0.4, 1t, 128MB, UHO_2024_8mvs_big_+115_+134.pgn):
Elo: 339.63 +/- 19.19, nElo: 552.46 +/- 17.58
LOS: 100.00 %, DrawRatio: 8.67 %, PairsRatio: 227.33
Games: 1500, Wins: 1188, Losses: 60, Draws: 252, Points: 1314.0 (87.60 %)
Ptnml(0-2): [0, 3, 65, 233, 449], WL/DD Ratio: 7.12
Assets 4
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