Added support for ELU activation

MLP/include/MLP.hpp

@@ -19,6 +19,7 @@ class MLP
     SIGMOID,
     TANH,
     RELU,
+    ELU,
     LINEAR,
     SPARSEMAX,
     CUBE,

MLP/src/MLP.cpp

@@ -15,6 +15,9 @@ std::string MLP::activation2str(Activation a)
     case RELU :
       return "RELU";
       break;
+    case ELU :
+      return "ELU";
+      break;
     case CUBE :
       return "CUBE";
       break;
@@ -43,6 +46,8 @@ MLP::Activation MLP::str2activation(std::string s)
     return LINEAR;
   else if(s == "RELU")
     return RELU;
+  else if(s == "ELU")
+    return ELU;
   else if(s == "CUBE")
     return CUBE;
   else if(s == "SIGMOID")
@@ -230,6 +235,9 @@ inline dynet::Expression MLP::activate(dynet::Expression h, Activation f)
     case RELU :
       return rectify(h);
       break;
+    case ELU :
+      return elu(h);
+      break;
     case SIGMOID :
       return logistic(h);
       break;