Moved the nnue folder.

src/nnue/features/enpassant.cpp

@@ -0,0 +1,47 @@
+//Definition of input feature quantity K of NNUE evaluation function
+
+#if defined(EVAL_NNUE)
+
+#include "enpassant.h"
+#include "index_list.h"
+
+namespace Eval {
+
+  namespace NNUE {
+
+    namespace Features {
+
+      // Get a list of indices with a value of 1 among the features
+      void EnPassant::AppendActiveIndices(
+        const Position& pos, Color perspective, IndexList* active) {
+        // do nothing if array size is small to avoid compiler warning
+        if (RawFeatures::kMaxActiveDimensions < kMaxActiveDimensions) return;
+
+        auto epSquare = pos.state()->epSquare;
+        if (epSquare == SQ_NONE) {
+          return;
+        }
+
+        if (perspective == BLACK) {
+          epSquare = Inv(epSquare);
+        }
+
+        auto file = file_of(epSquare);
+        active->push_back(file);
+      }
+
+      // Get a list of indices whose values ??have changed from the previous one in the feature quantity
+      void EnPassant::AppendChangedIndices(
+        const Position& pos, Color perspective,
+        IndexList* removed, IndexList* added) {
+        // Not implemented.
+        assert(false);
+      }
+
+    }  // namespace Features
+
+  }  // namespace NNUE
+
+}  // namespace Eval
+
+#endif  // defined(EVAL_NNUE)