Added scale_prev_ layer.

dlib/dnn/layers.h

@@ -2272,6 +2272,121 @@ namespace dlib
     using mult_prev9_  = mult_prev_<tag9>;
     using mult_prev10_ = mult_prev_<tag10>;
 
+// ----------------------------------------------------------------------------------------
+
+    template <
+        template<typename> class tag
+        >
+    class scale_prev_
+    {
+    public:
+        const static unsigned long id = tag_id<tag>::id;
+
+        scale_prev_() 
+        {
+        }
+
+        template <typename SUBNET>
+        void setup (const SUBNET& sub)
+        {
+            auto&& src = sub.get_output();
+            reshape_scales = alias_tensor(src.num_samples()*src.k());
+            reshape_src = alias_tensor(src.num_samples()*src.k(),src.nr()*src.nc());
+        }
+
+        template <typename SUBNET>
+        void forward(const SUBNET& sub, resizable_tensor& output)
+        {
+            auto&& src = sub.get_output();
+            auto&& scales = layer<tag>(sub).get_output();
+            DLIB_CASSERT(scales.num_samples() == src.num_samples() &&
+                         scales.k()           == src.k() &&
+                         scales.nr()          == 1 &&
+                         scales.nc()          == 1 );
+
+            output.copy_size(src);
+            tt::scale_channels(false, output, src, scales);
+        }
+
+        template <typename SUBNET>
+        void backward(const tensor& gradient_input, SUBNET& sub, tensor& /*params_grad*/)
+        {
+            auto&& src = sub.get_output();
+            auto&& scales = layer<tag>(sub).get_output();
+            // The gradient just flows backwards to the two layers that forward()
+            // read from.
+            tt::scale_channels(true, sub.get_gradient_input(), gradient_input, scales);
+
+            auto&& scales_grad = layer<tag>(sub).get_gradient_input();
+            auto sgrad = reshape_scales(scales_grad);
+            tt::dot_prods(true, sgrad, reshape_src(src), reshape_src(gradient_input));
+        }
+
+        const tensor& get_layer_params() const { return params; }
+        tensor& get_layer_params() { return params; }
+
+        friend void serialize(const scale_prev_& item, std::ostream& out)
+        {
+            serialize("scale_prev_", out);
+            serialize(item.reshape_scales, out);
+            serialize(item.reshape_src, out);
+        }
+
+        friend void deserialize(scale_prev_& item, std::istream& in)
+        {
+            std::string version;
+            deserialize(version, in);
+            if (version != "scale_prev_")
+                throw serialization_error("Unexpected version '"+version+"' found while deserializing dlib::scale_prev_.");
+            deserialize(item.reshape_scales, in);
+            deserialize(item.reshape_src, in);
+        }
+
+        friend std::ostream& operator<<(std::ostream& out, const scale_prev_& item)
+        {
+            out << "scale_prev"<<id;
+            return out;
+        }
+
+        friend void to_xml(const scale_prev_& item, std::ostream& out)
+        {
+            out << "<scale_prev tag='"<<id<<"'/>\n";
+        }
+
+    private:
+        alias_tensor reshape_scales;
+        alias_tensor reshape_src;
+        resizable_tensor params;
+    };
+
+    template <
+        template<typename> class tag,
+        typename SUBNET
+        >
+    using scale_prev = add_layer<scale_prev_<tag>, SUBNET>;
+
+    template <typename SUBNET> using scale_prev1  = scale_prev<tag1, SUBNET>;
+    template <typename SUBNET> using scale_prev2  = scale_prev<tag2, SUBNET>;
+    template <typename SUBNET> using scale_prev3  = scale_prev<tag3, SUBNET>;
+    template <typename SUBNET> using scale_prev4  = scale_prev<tag4, SUBNET>;
+    template <typename SUBNET> using scale_prev5  = scale_prev<tag5, SUBNET>;
+    template <typename SUBNET> using scale_prev6  = scale_prev<tag6, SUBNET>;
+    template <typename SUBNET> using scale_prev7  = scale_prev<tag7, SUBNET>;
+    template <typename SUBNET> using scale_prev8  = scale_prev<tag8, SUBNET>;
+    template <typename SUBNET> using scale_prev9  = scale_prev<tag9, SUBNET>;
+    template <typename SUBNET> using scale_prev10 = scale_prev<tag10, SUBNET>;
+
+    using scale_prev1_  = scale_prev_<tag1>;
+    using scale_prev2_  = scale_prev_<tag2>;
+    using scale_prev3_  = scale_prev_<tag3>;
+    using scale_prev4_  = scale_prev_<tag4>;
+    using scale_prev5_  = scale_prev_<tag5>;
+    using scale_prev6_  = scale_prev_<tag6>;
+    using scale_prev7_  = scale_prev_<tag7>;
+    using scale_prev8_  = scale_prev_<tag8>;
+    using scale_prev9_  = scale_prev_<tag9>;
+    using scale_prev10_ = scale_prev_<tag10>;
+
 // ----------------------------------------------------------------------------------------
 
     class relu_

dlib/dnn/layers_abstract.h

@@ -2326,6 +2326,76 @@ namespace dlib
     using mult_prev9_  = mult_prev_<tag9>;
     using mult_prev10_ = mult_prev_<tag10>;
 
+// ----------------------------------------------------------------------------------------
+
+    template <
+        template<typename> class tag
+        >
+    class scale_prev_
+    {
+        /*!
+            WHAT THIS OBJECT REPRESENTS
+                This is an implementation of the EXAMPLE_COMPUTATIONAL_LAYER_ interface
+                defined above.  This layer scales the output channels of the previous layer
+                by multiplying it with the output of the tagged layer.  To be specific:
+                    - Let INPUT  == sub.get_output()
+                    - Let SCALES == layer<tag>(sub).get_output()
+                    - This layer takes INPUT and SCALES as input.
+                    - The output of this layer has the same dimensions as INPUT.
+                    - This layer requires:
+                        - SCALES.num_samples() == INPUT.num_samples()
+                        - SCALES.k()  == INPUT.k()
+                        - SCALES.nr() == 1
+                        - SCALES.nc() == 1
+                    - The output tensor is produced by pointwise multiplying SCALES with
+                      INPUT at each spatial location.  Therefore, if OUT is the output of
+                      this layer then we would have:
+                        OUT(n,k,r,c) == INPUT(n,k,r,c)*SCALES(n,k)
+        !*/
+
+    public:
+        scale_prev_(
+        ); 
+
+        template <typename SUBNET> void setup (const SUBNET& sub);
+        template <typename SUBNET> void forward(const SUBNET& sub, resizable_tensor& output);
+        template <typename SUBNET> void backward(const tensor& gradient_input, SUBNET& sub, tensor& params_grad);
+        const tensor& get_layer_params() const; 
+        tensor& get_layer_params(); 
+        /*!
+            These functions are implemented as described in the EXAMPLE_COMPUTATIONAL_LAYER_ interface.
+        !*/
+    };
+
+
+    template <
+        template<typename> class tag,
+        typename SUBNET
+        >
+    using scale_prev = add_layer<scale_prev_<tag>, SUBNET>;
+
+    // Here we add some convenient aliases for using scale_prev_ with the tag layers. 
+    template <typename SUBNET> using scale_prev1  = scale_prev<tag1, SUBNET>;
+    template <typename SUBNET> using scale_prev2  = scale_prev<tag2, SUBNET>;
+    template <typename SUBNET> using scale_prev3  = scale_prev<tag3, SUBNET>;
+    template <typename SUBNET> using scale_prev4  = scale_prev<tag4, SUBNET>;
+    template <typename SUBNET> using scale_prev5  = scale_prev<tag5, SUBNET>;
+    template <typename SUBNET> using scale_prev6  = scale_prev<tag6, SUBNET>;
+    template <typename SUBNET> using scale_prev7  = scale_prev<tag7, SUBNET>;
+    template <typename SUBNET> using scale_prev8  = scale_prev<tag8, SUBNET>;
+    template <typename SUBNET> using scale_prev9  = scale_prev<tag9, SUBNET>;
+    template <typename SUBNET> using scale_prev10 = scale_prev<tag10, SUBNET>;
+    using scale_prev1_  = scale_prev_<tag1>;
+    using scale_prev2_  = scale_prev_<tag2>;
+    using scale_prev3_  = scale_prev_<tag3>;
+    using scale_prev4_  = scale_prev_<tag4>;
+    using scale_prev5_  = scale_prev_<tag5>;
+    using scale_prev6_  = scale_prev_<tag6>;
+    using scale_prev7_  = scale_prev_<tag7>;
+    using scale_prev8_  = scale_prev_<tag8>;
+    using scale_prev9_  = scale_prev_<tag9>;
+    using scale_prev10_ = scale_prev_<tag10>;
+
 // ----------------------------------------------------------------------------------------
 
     template<