From e386936ee911bde8891d5dd7810ae988e851e380 Mon Sep 17 00:00:00 2001
From: Jeff Donahue <jeff.donahue@gmail.com>
Date: Sat, 15 Feb 2014 12:07:02 -0800
Subject: [PATCH] make split_layer backward obey propagate_down

---
 src/caffe/layers/split_layer.cpp | 77 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)
 create mode 100644 src/caffe/layers/split_layer.cpp

diff --git a/src/caffe/layers/split_layer.cpp b/src/caffe/layers/split_layer.cpp
new file mode 100644
index 0000000..cdfd539
--- /dev/null
+++ b/src/caffe/layers/split_layer.cpp
@@ -0,0 +1,77 @@
+// Copyright 2014 Jeff Donahue
+
+#include <vector>
+
+#include "caffe/layer.hpp"
+#include "caffe/vision_layers.hpp"
+#include "caffe/util/math_functions.hpp"
+
+namespace caffe {
+
+template <typename Dtype>
+void SplitLayer<Dtype>::SetUp(const vector<Blob<Dtype>*>& bottom,
+      vector<Blob<Dtype>*>* top) {
+  CHECK_EQ(bottom.size(), 1) << "Split Layer takes a single blob as input.";
+  CHECK_GE(top->size(), 1) << "Split Layer takes at least one blob as output.";
+  count_ = bottom[0]->count();
+  for (int i = 0; i < top->size(); ++i) {
+    (*top)[i]->Reshape(bottom[0]->num(), bottom[0]->channels(),
+                       bottom[0]->height(), bottom[0]->width());
+    CHECK_EQ(count_, (*top)[i]->count());
+  }
+};
+
+template <typename Dtype>
+void SplitLayer<Dtype>::Forward_cpu(const vector<Blob<Dtype>*>& bottom,
+      vector<Blob<Dtype>*>* top) {
+  const Dtype* bottom_data = bottom[0]->cpu_data();
+  for (int i = 0; i < top->size(); ++i) {
+    Dtype* top_data = (*top)[i]->mutable_cpu_data();
+    caffe_copy(count_, bottom_data, top_data);
+  }
+}
+
+template <typename Dtype>
+void SplitLayer<Dtype>::Forward_gpu(const vector<Blob<Dtype>*>& bottom,
+      vector<Blob<Dtype>*>* top) {
+  const Dtype* bottom_data = bottom[0]->gpu_data();
+  for (int i = 0; i < top->size(); ++i) {
+    Dtype* top_data = (*top)[i]->mutable_gpu_data();
+    caffe_gpu_copy(count_, bottom_data, top_data);
+  }
+}
+
+template <typename Dtype>
+Dtype SplitLayer<Dtype>::Backward_cpu(const vector<Blob<Dtype>*>& top,
+      const bool propagate_down, vector<Blob<Dtype>*>* bottom) {
+  if (propagate_down) {
+    const Dtype* top_diff = top[0]->cpu_diff();
+    Dtype* bottom_diff = (*bottom)[0]->mutable_cpu_diff();
+    caffe_copy(count_, top_diff, bottom_diff);
+    for (int i = 1; i < top.size(); ++i) {
+      top_diff = top[i]->cpu_diff();
+      caffe_axpy(count_, Dtype(1.), top_diff, bottom_diff);
+    }
+  }
+  return Dtype(0.);
+}
+
+
+template <typename Dtype>
+Dtype SplitLayer<Dtype>::Backward_gpu(const vector<Blob<Dtype>*>& top,
+      const bool propagate_down, vector<Blob<Dtype>*>* bottom) {
+  if (propagate_down) {
+    const Dtype* top_diff = top[0]->gpu_diff();
+    Dtype* bottom_diff = (*bottom)[0]->mutable_gpu_diff();
+    caffe_gpu_copy(count_, top_diff, bottom_diff);
+    for (int i = 1; i < top.size(); ++i) {
+      top_diff = top[i]->gpu_diff();
+      caffe_gpu_axpy(count_, Dtype(1.), top_diff, bottom_diff);
+    }
+  }
+  return Dtype(0.);
+}
+
+INSTANTIATE_CLASS(SplitLayer);
+
+}  // namespace caffe
-- 
2.7.4