Add BN layer from BVLC/caffe PR BVLC#1965

Added bn_layer.[cpp/cu] with corresponding hpp file.
Performs batch-normalization with in-place scale/shift.

Originally created by
ducha-aiki: https://github.com/ducha-aiki
ChenglongChen: https://github.com/ChenglongChen
Russell91: https://github.com/Russell91
jjkjkj: https://github.com/jjkjkj

detailed discussion of this implementation can be found at:
BVLC#1965

include/caffe/layers/bn_layer.hpp

@@ -0,0 +1,79 @@
+#ifndef CAFFE_BN_LAYER_HPP_
+#define CAFFE_BN_LAYER_HPP_
+
+#include <vector>
+
+#include "caffe/blob.hpp"
+#include "caffe/layer.hpp"
+#include "caffe/proto/caffe.pb.h"
+#include "caffe/util/math_functions.hpp"
+
+namespace caffe {
+
+/**
+* @brief Batch Normalization per-channel with scale & shift linear transform.
+*
+*/
+template <typename Dtype>
+class BNLayer : public Layer<Dtype> {
+ /*
+ notice:
+ this code is based on the implementation of by following authors.
+
+ ducha-aiki: https://github.com/ducha-aiki
+ ChenglongChen: https://github.com/ChenglongChen
+ Russell91: https://github.com/Russell91
+ jjkjkj: https://github.com/jjkjkj
+
+ detailed discussion of this implementation can be found at:
+ https://github.com/BVLC/caffe/pull/1965
+ */
+ public:
+  explicit BNLayer(const LayerParameter& param)
+      : Layer<Dtype>(param) {}
+  virtual void LayerSetUp(const vector<Blob<Dtype>*>& bottom,
+      const vector<Blob<Dtype>*>& top);
+  virtual void Reshape(const vector<Blob<Dtype>*>& bottom,
+      const vector<Blob<Dtype>*>& top);
+  virtual inline const char* type() const { return "BN"; }
+  virtual inline int ExactNumBottomBlobs() const { return 1; }
+  virtual inline int MinTopBlobs() const { return 1; }
+  // if the BNMode is "LEARN" mamximum 3 top blobs are available
+  virtual inline int MaxTopBlobs() const {
+    return (this->layer_param_.bn_param().bn_mode() ==
+            BNParameter_BNMode_LEARN) ? 3 : 1;
+  }
+
+ protected:
+  virtual void Forward_cpu(const vector<Blob<Dtype>*>& bottom,
+      const vector<Blob<Dtype>*>& top);
+  virtual void Forward_gpu(const vector<Blob<Dtype>*>& bottom,
+      const vector<Blob<Dtype>*>& top);
+  virtual void Backward_cpu(const vector<Blob<Dtype>*>& top,
+      const vector<bool>& propagate_down, const vector<Blob<Dtype>*>& bottom);
+  virtual void Backward_gpu(const vector<Blob<Dtype>*>& top,
+      const vector<bool>& propagate_down, const vector<Blob<Dtype>*>& bottom);
+
+  // spatial mean & variance
+  Blob<Dtype> spatial_mean_, spatial_variance_;
+  // batch mean & variance
+  Blob<Dtype> batch_mean_, batch_variance_;
+  // buffer blob
+  Blob<Dtype> buffer_blob_;
+
+  Blob<Dtype> x_norm_;
+  // x_sum_multiplier is used to carry out sum using BLAS
+  Blob<Dtype> spatial_sum_multiplier_, batch_sum_multiplier_;
+
+  // dimension
+  int N_;
+  int C_;
+  int H_;
+  int W_;
+  // eps
+  Dtype var_eps_;
+};
+
+}  // namespace caffe
+
+#endif  // CAFFE_BN_LAYER_HPP_