Luna Chess-Engine (LCE) 3.1.7 - new version chess engine for Android

Luna Chess Engine
Luna is a high-performance chess engine written in Rust, designed for efficiency and strength. It combines classical bitboard-based move generation with a state-of-the-art NNUE (Efficiently Updatable Neural Network) evaluation, allowing for deep positional understand in.

Author: Spunc595

Luna Chess-Engine (LCE) JA what's new?

Evaluation: akimbo's material scaling factor, now applied

Luna's embedded NNUE network is akimbo's, used as-is under its MIT license.

akimbo scales the network's output at search time by a factor that depends on

the material left on the board. Luna was not applying it.

The factor lowers evaluations, and lowers them most in the endgame, where the

multiplier reaches its minimum. It is not a uniform rescaling: it depends on

material, which changes inside the search tree at every capture, so it directly

affects exchange decisions.

Two things are established:

It reproduces the reference implementation exactly. With the factor

applied, Luna's evaluation matches akimbo's with zero difference across 2000

positions — checked against an akimbo binary built at the commit that

introduced the network, not against a reimplementation.

It wins games. Accepted by SPRT at 10+0.1, bounds [0, 10],

alpha = beta = 0.05, with zero losses on time.

One thing is not. The obvious explanation — that the network was trained with

the factor active, so its raw output expects to be scaled afterwards — does not

hold: akimbo's own data-generation build disables the factor, and the trainer

applies no output scaling. So this is an empirical search-time correction that

matches the reference engine and measurably gains strength, with the mechanism

still open. It is described here as what it is rather than as what it would be

convenient for it to be.

No Elo figure is published for this change. The SPRT estimate comes from a run

that stopped early, which biases it upward, and an unbiased fixed-length

measurement has not been made.

Luna Chess-Engine (LCE) 3.1.7 download

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