Ensure stable count for nnueKing

diff --git a/src/variant.h b/src/variant.h
index a6dbee5..085e9b4 100644 (file)
--- a/src/variant.h
+++ b/src/variant.h
@@ -241,6 +241,15 @@ struct Variant {
       nnueKing =  pieceTypes & KING ? KING
                 : extinctionPieceCount == 0 && (extinctionPieceTypes & COMMONER) ? COMMONER
                 : NO_PIECE_TYPE;
+      // The nnueKing has to present exactly once and must not change in count
+      if (nnueKing != NO_PIECE_TYPE)
+      {
+          // If the nnueKing is involved in promotion, count might change
+          if (   ((promotionPawnTypes[WHITE] | promotionPawnTypes[BLACK]) & nnueKing)
+              || ((promotionPieceTypes[WHITE] | promotionPieceTypes[BLACK]) & nnueKing)
+              || std::find(std::begin(promotedPieceType), std::end(promotedPieceType), nnueKing) != std::end(promotedPieceType))
+              nnueKing = NO_PIECE_TYPE;
+      }
       if (nnueKing != NO_PIECE_TYPE)
       {
           std::string fenBoard = startFen.substr(0, startFen.find(' '));