Add ELU layer

Author: fohx13

include/af/nn/Modules/Activations.hpp

@@ -58,5 +58,16 @@ namespace af
             autograd::Variable forward(const autograd::Variable &input);
         };
 
+        class ELU : public Module
+        {
+        private:
+            double m_alpha;
+        public:
+            ELU(double alpha = 1.0);
+
+            autograd::Variable forward(const autograd::Variable &input);
+        };
+      
+
     }
 }

src/nn/Modules/Activations.cpp

@@ -67,5 +67,16 @@ namespace af
 
         }
 
+        ELU::ELU(double alpha) :
+          m_alpha(alpha)
+        {
+        }
+
+        Variable ELU::forward(const Variable &input)
+        {
+            auto res = max(input, m_alpha * (exp(input) - 1));
+            return res;
+        }
+      
     }
 }