Sync public subset from Flux

include/modules/neural_networks/loss/Loss.h

@@ -0,0 +1,32 @@
+#pragma once
+
+#include "./core/omp_config.h"
+
+#include "./utils/vector.h"
+#include "./utils/matrix.h"
+
+#include "./numerics/vecmean.h"
+
+namespace neural_networks{
+
+	template <typename Td, typename Ti>
+	struct Loss{
+
+			utils::Vector<Td> sample_losses;
+			Td data_loss;
+
+			virtual utils::Vector<Td> forward(const utils::Matrix<Td>& output, const utils::Matrix<Ti>& y) = 0;
+
+			Td calculate(const utils::Matrix<Td>& output, const utils::Matrix<Ti>& y){
+				
+				// Calculate sample losses
+				sample_losses = forward(output, y);
+
+				// Calculate mean loss
+				data_loss = numerics::vecmean(sample_losses);
+				return data_loss;
+
+			}
+	};
+
+} // end namespace neural_networks