Optimized eigen kernel for spatial mean (#1094)

* Optimized eigen kernel for 2D reduction on a 4D tensor used for spatial mean

* revert change to serializer

src/ngraph/runtime/cpu/cpu_emitter.cpp

@@ -2095,6 +2095,16 @@ namespace ngraph
                            << "{" << join(sum->get_reduction_axes()) << "}"
                            << ");\n";
                 }
+                else if (args[0].get_element_type() == element::f32 &&
+                         args[0].get_shape().size() == 4 && sum->get_reduction_axes().size() == 2)
+                {
+                    writer << "cpu::kernel::reduce_sum_4d_2rd_float32(" << args[0].get_name()
+                           << ", " << out[0].get_name() << ", "
+                           << "{" << join(args[0].get_shape()) << "}, "
+                           << "{" << join(out[0].get_shape()) << "}, "
+                           << "{" << join(sum->get_reduction_axes()) << "}"
+                           << ");\n";
+                }
                 else if (args[0].get_element_type() == element::f32 &&
                          args[0].get_shape().size() == 4 && sum->get_reduction_axes().size() == 4)
                 {

src/ngraph/runtime/cpu/cpu_kernels.hpp

@@ -158,6 +158,12 @@ namespace ngraph
                                                const Shape& output_shape,
                                                const AxisSet& reduction_axes);
 
+                void reduce_sum_4d_2rd_float32(float* input,
+                                               float* output,
+                                               const Shape& input_shape,
+                                               const Shape& output_shape,
+                                               const AxisSet& reduction_axes);
+
                 void reduce_sum_all_4d_float32(float* input,
                                                float* output,
                                                const Shape& input_shape,

src/ngraph/runtime/cpu/kernel/reduce_sum.cpp

@@ -57,6 +57,15 @@ namespace ngraph
                 {
                     reduce_sum_all<float, 4>(input, output, input_shape, output_shape);
                 }
+                void reduce_sum_4d_2rd_float32(float* input,
+                                               float* output,
+                                               const Shape& input_shape,
+                                               const Shape& output_shape,
+                                               const AxisSet& reduction_axes)
+                {
+                    reduce_sum<float, 4, 2>(
+                        input, output, input_shape, output_shape, reduction_axes);
+                }
             }
         }
     }