add CropLayer for cropping one blob to another using induced coordinates

include/caffe/vision_layers.hpp

@@ -453,6 +453,41 @@ class CuDNNPoolingLayer : public PoolingLayer<Dtype> {
 };
 #endif
 
+template <typename Dtype>
+class CropLayer : public Layer<Dtype> {
+ public:
+  explicit CropLayer(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 LayerParameter_LayerType type() const {
+    return LayerParameter_LayerType_CROP;
+  }
+  virtual inline int ExactNumBottomBlobs() const { return 2; }
+  virtual inline int ExactNumTopBlobs() const { return 1; }
+  virtual inline DiagonalAffineMap<Dtype> coord_map() {
+    vector<pair<Dtype, Dtype> > coefs;
+    coefs.push_back(make_pair(1, - crop_h_));
+    coefs.push_back(make_pair(1, - crop_w_));
+    return DiagonalAffineMap<Dtype>(coefs);
+  }
+
+ protected:
+  virtual void Forward_cpu(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 Forward_gpu(const vector<Blob<Dtype>*>& bottom,
+      const vector<Blob<Dtype>*>& top);
+  virtual void Backward_gpu(const vector<Blob<Dtype>*>& top,
+      const vector<bool>& propagate_down, const vector<Blob<Dtype>*>& bottom);
+
+  int crop_h_, crop_w_;
+};
+
 }  // namespace caffe
 
 #endif  // CAFFE_VISION_LAYERS_HPP_

src/caffe/layers/crop_layer.cpp

@@ -0,0 +1,126 @@
+#include <algorithm>
+#include <map>
+#include <set>
+#include <vector>
+
+#include "caffe/layer.hpp"
+#include "caffe/net.hpp"
+#include "caffe/vision_layers.hpp"
+
+namespace caffe {
+
+template <typename Dtype>
+void CropLayer<Dtype>::LayerSetUp(const vector<Blob<Dtype>*>& bottom,
+    const vector<Blob<Dtype>*>& top) {
+  // Construct a map from top blobs to layer inds, skipping over in-place
+  // connections.
+  map<Blob<Dtype>*, int> down_map;
+  for (int layer_ind = 0; layer_ind < this->net_->top_vecs().size();
+       ++layer_ind) {
+    vector<Blob<Dtype>*> tops = this->net_->top_vecs()[layer_ind];
+    for (int top_ind = 0; top_ind < tops.size(); ++top_ind) {
+      if (down_map.find(tops[top_ind]) == down_map.end()) {
+        down_map[tops[top_ind]] = layer_ind;
+      }
+    }
+  }
+  // Walk back from the first bottom, keeping track of all the blobs we pass.
+  set<Blob<Dtype>*> path_blobs;
+  Blob<Dtype>* blob = bottom[0];
+  int layer_ind;
+  // TODO this logic can be simplified if all blobs are tops
+  path_blobs.insert(blob);
+  while (down_map.find(blob) != down_map.end()) {
+    layer_ind = down_map[blob];
+    if (this->net_->bottom_vecs()[layer_ind].size() == 0) {
+      break;
+    }
+    blob = this->net_->bottom_vecs()[layer_ind][0];
+    path_blobs.insert(blob);
+  }
+  // Now walk back from the second bottom, until we find a blob of intersection.
+  Blob<Dtype>* inter_blob = bottom[1];
+  while (path_blobs.find(inter_blob) == path_blobs.end()) {
+    CHECK(down_map.find(inter_blob) != down_map.end())
+        << "Cannot align apparently disconnected blobs.";
+    layer_ind = down_map[inter_blob];
+    CHECK_GT(this->net_->bottom_vecs()[layer_ind].size(), 0)
+        << "Cannot align apparently disconnected blobs.";
+    inter_blob = this->net_->bottom_vecs()[layer_ind][0];
+  }
+  // Compute the coord map from the blob of intersection to each bottom.
+  vector<DiagonalAffineMap<Dtype> > coord_maps(2,
+      DiagonalAffineMap<Dtype>::identity(2));
+  for (int i = 0; i < 2; ++i) {
+    for (Blob<Dtype>* blob = bottom[i]; blob != inter_blob;
+         blob = this->net_->bottom_vecs()[down_map[blob]][0]) {
+      shared_ptr<Layer<Dtype> > layer = this->net_->layers()[down_map[blob]];
+      coord_maps[i] = coord_maps[i].compose(layer->coord_map());
+    }
+  }
+  // Compute the mapping from first bottom coordinates to second.
+  DiagonalAffineMap<Dtype> crop_map =
+      coord_maps[1].compose(coord_maps[0].inv());
+  for (int i = 0; i < 2; ++i) {
+    // Check for scale mismatch (unfortunately, CHECK_DOUBLE_EQ does not
+    // support a message like the other CHECKs).
+    CHECK_DOUBLE_EQ(crop_map.coefs()[i].first, 1);
+    CHECK_LE(crop_map.coefs()[i].second, 0) << "Negative crop width.";
+    // Check that the crop width is an integer.
+    CHECK_DOUBLE_EQ(crop_map.coefs()[i].second,
+        round(crop_map.coefs()[i].second));
+  }
+  crop_h_ = - round(crop_map.coefs()[0].second);
+  crop_w_ = - round(crop_map.coefs()[1].second);
+}
+
+template <typename Dtype>
+void CropLayer<Dtype>::Reshape(const vector<Blob<Dtype>*>& bottom,
+    const vector<Blob<Dtype>*>& top) {
+  top[0]->Reshape(bottom[0]->num(), bottom[0]->channels(), bottom[1]->height(),
+      bottom[1]->width());
+}
+
+template <typename Dtype>
+void CropLayer<Dtype>::Forward_cpu(const vector<Blob<Dtype>*>& bottom,
+    const vector<Blob<Dtype>*>& top) {
+  const Dtype* bottom_data = bottom[0]->cpu_data();
+  Dtype* top_data = top[0]->mutable_cpu_data();
+  for (int n = 0; n < top[0]->num(); ++n) {
+    for (int c = 0; c < top[0]->channels(); ++c) {
+      for (int h = 0; h < top[0]->height(); ++h) {
+        caffe_copy(top[0]->width(),
+            bottom_data + bottom[0]->offset(n, c, crop_h_ + h, crop_w_),
+            top_data + top[0]->offset(n, c, h));
+      }
+    }
+  }
+}
+
+template <typename Dtype>
+void CropLayer<Dtype>::Backward_cpu(const vector<Blob<Dtype>*>& top,
+    const vector<bool>& propagate_down, const vector<Blob<Dtype>*>& bottom) {
+  const Dtype* top_diff = top[0]->cpu_diff();
+  Dtype* bottom_diff = bottom[0]->mutable_cpu_diff();
+  if (propagate_down[0]) {
+    caffe_set(bottom[0]->count(), static_cast<Dtype>(0), bottom_diff);
+    for (int n = 0; n < top[0]->num(); ++n) {
+      for (int c = 0; c < top[0]->channels(); ++c) {
+        for (int h = 0; h < top[0]->height(); ++h) {
+          caffe_copy(top[0]->width(),
+              top_diff + top[0]->offset(n, c, h),
+              bottom_diff + bottom[0]->offset(n, c, crop_h_ + h, crop_w_));
+        }
+      }
+    }
+  }
+}
+
+#ifdef CPU_ONLY
+STUB_GPU(CropLayer);
+#endif
+
+INSTANTIATE_CLASS(CropLayer);
+REGISTER_LAYER_CLASS(CROP, CropLayer);
+
+}  // namespace caffe

src/caffe/layers/crop_layer.cu

@@ -0,0 +1,60 @@
+#include <vector>
+
+#include "caffe/vision_layers.hpp"
+
+namespace caffe {
+
+// Copy (one line per thread) from one array to another, with arbitrary
+// strides in the last two dimensions.
+template <typename Dtype>
+__global__ void copy_kernel(const int n, const int height, const int width,
+    const int src_outer_stride, const int src_inner_stride,
+    const int dest_outer_stride, const int dest_inner_stride,
+    const Dtype* src, Dtype* dest) {
+  CUDA_KERNEL_LOOP(index, n) {
+    int src_start = index / height * src_outer_stride
+                  + index % height * src_inner_stride;
+    int dest_start = index / height * dest_outer_stride
+                   + index % height * dest_inner_stride;
+    for (int i = 0; i < width; ++i) {
+      dest[dest_start + i] = src[src_start + i];
+    }
+  }
+}
+
+template <typename Dtype>
+void CropLayer<Dtype>::Forward_gpu(const vector<Blob<Dtype>*>& bottom,
+    const vector<Blob<Dtype>*>& top) {
+  const Dtype* bottom_data = bottom[0]->gpu_data();
+  Dtype* top_data = top[0]->mutable_gpu_data();
+  const int lines = top[0]->count() / top[0]->width();
+
+  // NOLINT_NEXT_LINE(whitespace/operators)
+  copy_kernel<<<CAFFE_GET_BLOCKS(lines), CAFFE_CUDA_NUM_THREADS>>>(
+      lines, top[0]->height(), top[0]->width(),
+      bottom[0]->height() * bottom[0]->width(), bottom[0]->width(),
+      top[0]->height() * top[0]->width(), top[0]->width(),
+      bottom_data + bottom[0]->offset(0, 0, crop_h_, crop_w_), top_data);
+}
+
+template <typename Dtype>
+void CropLayer<Dtype>::Backward_gpu(const vector<Blob<Dtype>*>& top,
+    const vector<bool>& propagate_down, const vector<Blob<Dtype>*>& bottom) {
+  const Dtype* top_diff = top[0]->gpu_diff();
+  Dtype* bottom_diff = bottom[0]->mutable_gpu_diff();
+  const int lines = top[0]->count() / top[0]->width();
+
+  if (propagate_down[0]) {
+    caffe_gpu_set(bottom[0]->count(), static_cast<Dtype>(0), bottom_diff);
+    // NOLINT_NEXT_LINE(whitespace/operators)
+    copy_kernel<<<CAFFE_GET_BLOCKS(lines), CAFFE_CUDA_NUM_THREADS>>>(
+        lines, top[0]->height(), top[0]->width(),
+        top[0]->height() * top[0]->width(), top[0]->width(),
+        bottom[0]->height() * bottom[0]->width(), bottom[0]->width(),
+        top_diff, bottom_diff + bottom[0]->offset(0, 0, crop_h_, crop_w_));
+  }
+}
+
+INSTANTIATE_LAYER_GPU_FUNCS(CropLayer);
+
+}  // namespace caffe

src/caffe/proto/caffe.proto

@@ -227,7 +227,7 @@ message LayerParameter {
   // line above the enum. Update the next available ID when you add a new
   // LayerType.
   //
-  // LayerType next available ID: 40 (last added: DECONVOLUTION)
+  // LayerType next available ID: 41 (last added: CROP)
   enum LayerType {
     // "NONE" layer type is 0th enum element so that we don't cause confusion
     // by defaulting to an existent LayerType (instead, should usually error if
@@ -240,6 +240,7 @@ message LayerParameter {
     CONCAT = 3;
     CONTRASTIVE_LOSS = 37;
     CONVOLUTION = 4;
+    CROP = 40;
     DATA = 5;
     DECONVOLUTION = 39;
     DROPOUT = 6;