allways fill history for en passant (LeelaChessZero#1837)

(cherry picked from commit 3a88534)
uwuplant · Feb 2, 2023 · eee9ec2 · eee9ec2
1 parent 27ef14e
commit eee9ec2
Showing 1 changed file with 6 additions and 1 deletion.
diff --git a/src/neural/encoder.cc b/src/neural/encoder.cc
@@ -247,7 +247,12 @@ InputPlanes EncodePositionForNN(
         !board.en_passant().empty()) {
       break;
     }
-    if (history_idx < 0 && fill_empty_history == FillEmptyHistory::NO) break;
+    // If en-passant is possible we know the previous move.
+    if (fill_empty_history == FillEmptyHistory::NO &&
+        (history_idx < -1 ||
+         (history_idx == -1 && board.en_passant().empty()))) {
+      break;
+    }
     // Board may be flipped so compare with position.GetBoard().
     if (history_idx < 0 && fill_empty_history == FillEmptyHistory::FEN_ONLY &&
         position.GetBoard() == ChessBoard::kStartposBoard) {