Added operator<< for the DNN solvers.

dlib/dnn/solvers.h

@@ -119,6 +119,12 @@ namespace dlib
             deserialize(item.momentum, in);
         }
 
+        friend std::ostream& operator<< (std::ostream& out, const sgd& item)
+        {
+            out << "sgd: weight_decay="<<item.get_weight_decay() << ", momentum="<<item.get_momentum(); 
+            return out;
+        }
+
     private:
 
         template <typename layer_type> 
@@ -294,6 +300,12 @@ namespace dlib
             deserialize(item.t, in);
         }
 
+        friend std::ostream& operator<< (std::ostream& out, const adam& item)
+        {
+            out << "adam: weight_decay="<<item.get_weight_decay() << ", momentum1="<<item.get_momentum1() << ", momentum2="<<item.get_momentum2(); 
+            return out;
+        }
+
     private:
 
         template <typename layer_type> 

dlib/dnn/solvers_abstract.h

@@ -64,6 +64,11 @@ namespace dlib
         provides serialization support  
     !*/
 
+    std::ostream& operator<< (std::ostream& out, const EXAMPLE_SOLVER& item);
+    /*!
+        Prints the solver's name and parameters to out.
+    !*/
+
 // ----------------------------------------------------------------------------------------
 // ----------------------------------------------------------------------------------------
 // ----------------------------------------------------------------------------------------
@@ -121,6 +126,11 @@ namespace dlib
         provides serialization support  
     !*/
 
+    std::ostream& operator<< (std::ostream& out, const sgd& item);
+    /*!
+        Prints the solver's name and parameters to out.
+    !*/
+
 // ----------------------------------------------------------------------------------------
 
     class adam
@@ -181,6 +191,11 @@ namespace dlib
         provides serialization support  
     !*/
 
+    std::ostream& operator<< (std::ostream& out, const adam& item);
+    /*!
+        Prints the solver's name and parameters to out.
+    !*/
+
 // ----------------------------------------------------------------------------------------
 
 }