From 839b0502648a5dcf056c3f4a6ace1d0198e6b03e Mon Sep 17 00:00:00 2001
From: Evan Shelhamer <shelhamer@imaginarynumber.net>
Date: Fri, 4 Mar 2016 15:35:16 -0800
Subject: [PATCH] share columnation buffers for convolution to save memory

share the im2col / col2im buffers among convolution + deconvolution
layers by making the buffer a static member.

@longjon deserves all the credit for the reshaping #594 and this patch.
---
 include/caffe/layers/base_conv_layer.hpp | 4 +++-
 src/caffe/layers/base_conv_layer.cpp     | 3 +++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/include/caffe/layers/base_conv_layer.hpp b/include/caffe/layers/base_conv_layer.hpp
index 0160a833dd2..8cdbd2d1b43 100644
--- a/include/caffe/layers/base_conv_layer.hpp
+++ b/include/caffe/layers/base_conv_layer.hpp
@@ -165,7 +165,9 @@ class BaseConvolutionLayer : public Layer<Dtype> {
   int col_offset_;
   int output_offset_;
 
-  Blob<Dtype> col_buffer_;
+  // N.B. sharing the col buffer reduces memory but interferes with
+  // ND conv and parallelism
+  static Blob<Dtype> col_buffer_;
   Blob<Dtype> bias_multiplier_;
 };
 
diff --git a/src/caffe/layers/base_conv_layer.cpp b/src/caffe/layers/base_conv_layer.cpp
index 4a4c68e009a..8a7b5e8c8d3 100644
--- a/src/caffe/layers/base_conv_layer.cpp
+++ b/src/caffe/layers/base_conv_layer.cpp
@@ -8,6 +8,9 @@
 
 namespace caffe {
 
+template <typename Dtype>
+Blob<Dtype> BaseConvolutionLayer<Dtype>::col_buffer_;
+
 template <typename Dtype>
 void BaseConvolutionLayer<Dtype>::LayerSetUp(const vector<Blob<Dtype>*>& bottom,
       const vector<Blob<Dtype>*>& top) {