Janis Eccarius
2a3f0d6be3
Build & Test (NowChessSystems) TeamCity build failed
Training: for Black-to-move positions, mirror the board (ranks flipped,
colours swapped) before feature extraction so the model always sees the
position from the side-to-move's perspective. Eval label is negated to
match. Implemented in fen_to_features (board.mirror()) and __getitem__
(' b ' check in FEN string).
Inference (legacy evaluate()): applies the same flip for Black so the
model receives features in the format it was trained on. The
scoreFromOutput negation converts back to White's absolute perspective.
Incremental accumulator path is unchanged — it uses the raw HalfKP
features with the existing sign-negation at output; the quality gain comes
from the richer training distribution.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>