Added get_learning_rate_multiplier() and get_weight_decay_multiplier() global

functions.

dlib/algs.h

@@ -488,6 +488,13 @@ namespace dlib
 
 // ----------------------------------------------------------------------------------------
 
+    struct general_ {};
+    struct special_ : general_ {};
+    template<typename> struct int_ { typedef int type; };
+
+// ----------------------------------------------------------------------------------------
+
+
     /*!A is_same_object 
 
         This is a templated function which checks if both of its arguments are actually

dlib/dnn/core.h

@@ -24,6 +24,38 @@
 namespace dlib
 {
 
+// ----------------------------------------------------------------------------------------
+
+    namespace impl
+    {
+        template <typename T, typename int_<decltype(&T::get_learning_rate_multiplier)>::type = 0>
+        double get_learning_rate_multiplier (
+            const T& obj,
+            special_
+        ) { return obj.get_learning_rate_multiplier(); }
+
+        template <typename T>
+        double get_learning_rate_multiplier ( const T& obj, general_) { return 1; }
+    }
+    template <typename T>
+    double get_learning_rate_multiplier(const T& obj) { return impl::get_learning_rate_multiplier(obj, special_()); }
+
+// ----------------------------------------------------------------------------------------
+
+    namespace impl
+    {
+        template <typename T, typename int_<decltype(&T::get_weight_decay_multiplier)>::type = 0>
+        double get_weight_decay_multiplier (
+            const T& obj,
+            special_
+        ) { return obj.get_weight_decay_multiplier(); }
+
+        template <typename T>
+        double get_weight_decay_multiplier ( const T& obj, general_) { return 1; }
+    }
+    template <typename T>
+    double get_weight_decay_multiplier(const T& obj) { return impl::get_weight_decay_multiplier(obj, special_()); }
+
 // ----------------------------------------------------------------------------------------
 
     namespace impl
@@ -849,8 +881,9 @@ namespace dlib
         void update_parameters(sstack<solver_type> solvers, double learning_rate)
         {
             DLIB_CASSERT(solvers.size()>=num_computational_layers,"");
-            // Don't try to adjust the parameters if this layer doesn't have any.
-            if (params_grad.size() != 0)
+            // Don't try to adjust the parameters if this layer doesn't have any or the
+            // learning rate is disabled for this layer.
+            if (params_grad.size() != 0 && get_learning_rate_multiplier(details) != 0)
             {
                 const tensor& step = solvers.top()(learning_rate, details, static_cast<const tensor&>(params_grad));
                 tt::add(details.get_layer_params(), details.get_layer_params(), step);
@@ -1200,8 +1233,9 @@ namespace dlib
         void update_parameters(sstack<solver_type> solvers, double learning_rate)
         {
             DLIB_CASSERT(solvers.size()>=num_computational_layers,"");
-            // Don't try to adjust the parameters if this layer doesn't have any.
-            if (params_grad.size() != 0) 
+            // Don't try to adjust the parameters if this layer doesn't have any or the
+            // learning rate is disabled for this layer.
+            if (params_grad.size() != 0 && get_learning_rate_multiplier(details) != 0) 
             {
                 const tensor& step = solvers.top()(learning_rate, details, static_cast<const tensor&>(params_grad));
                 tt::add(details.get_layer_params(), details.get_layer_params(), step);

dlib/dnn/core_abstract.h

@@ -67,6 +67,32 @@ namespace dlib
               (except computes it using a numerically accurate method)
     !*/
 
+// ----------------------------------------------------------------------------------------
+
+    template <typename T>
+    double get_learning_rate_multiplier(
+        const T& obj
+    ); 
+    /*!
+        ensures
+            - if (obj has a get_learning_rate_multiplier() member function) then
+                - returns obj.get_learning_rate_multiplier()
+            - else
+                - returns 1
+    !*/
+
+    template <typename T>
+    double get_weight_decay_multiplier(
+        const T& obj
+    ); 
+    /*!
+        ensures
+            - if (obj has a get_weight_decay_multiplier() member function) then
+                - returns obj.get_weight_decay_multiplier()
+            - else
+                - returns 1
+    !*/
+
 // ----------------------------------------------------------------------------------------
 
     bool dnn_prefer_fastest_algorithms(