Merge pull request #287 from gangliao/bilinear

Add bilinear interpolation layer

doc/ui/api/trainer_config_helpers/layers.rst

@@ -275,6 +275,12 @@ interpolation_layer
     :members: interpolation_layer
     :noindex:
 
+bilinear_interp_layer
+----------------------
+..  automodule:: paddle.trainer_config_helpers.layers
+    :members: bilinear_interp_layer
+    :noindex:
+
 power_layer
 -----------
 ..  automodule:: paddle.trainer_config_helpers.layers

paddle/cuda/include/hl_cnn.h

@@ -240,6 +240,70 @@ extern void hl_CMRNorm_backward(
     size_t channels, size_t height, size_t width, size_t sizeX,
     real alpha, real beta);
 
+/**
+ * @brief   Bilinear interpolation forward.
+ *
+ * @param[in]   inData      input value.
+ * @param[in]   inImgH      input image height.
+ * @param[in]   inImgW      input image width.
+ * @param[in]   inputH      input batchSize.
+ * @param[in]   inputW      input image data dim.
+ * @param[out]  outData     output value.
+ * @param[in]   outImgH     output image height.
+ * @param[in]   outImgW     output image width.
+ * @param[in]   outputH     output batchSize.
+ * @param[in]   outputW     output image data dim.
+ * @param[in]   numChannels number of channels.
+ * @param[in]   ratioH      inImgH / outImgH.
+ * @param[in]   ratioW      inImgW / outImgW.
+ *
+ */
+extern void hl_bilinear_forward(const real* inData,
+                                const size_t inImgH,
+                                const size_t inImgW,
+                                const size_t inputH,
+                                const size_t inputW,
+                                real* outData,
+                                const size_t outImgH,
+                                const size_t outImgW,
+                                const size_t outputH,
+                                const size_t outputW,
+                                const size_t numChannels,
+                                const real ratioH,
+                                const real ratioW);
+
+ /**
+ * @brief   Bilinear interpolation backward.
+ *
+ * @param[out]  inGrad      input gradient.
+ * @param[in]   inImgH      input image height.
+ * @param[in]   inImgW      input image width.
+ * @param[in]   inputH      input batchSize.
+ * @param[in]   inputW      input image data dim.
+ * @param[in]   outGrad     output gradient.
+ * @param[in]   outImgH     output image height.
+ * @param[in]   outImgW     output image width.
+ * @param[in]   outputH     output batchSize.
+ * @param[in]   outputW     output image data dim.
+ * @param[in]   numChannels number of channels.
+ * @param[in]   ratioH      inImgH / outImgH.
+ * @param[in]   ratioW      inImgW / outImgW.
+ *
+ */                               
+extern void hl_bilinear_backward(real* inGrad,
+                                 const size_t inImgH,
+                                 const size_t inImgW,
+                                 const size_t inputH,
+                                 const size_t inputW,
+                                 const real* outGrad,
+                                 const size_t outImgH,
+                                 const size_t outImgW,
+                                 const size_t outputH,
+                                 const size_t outputW,
+                                 const size_t numChannels,
+                                 const real ratioH,
+                                 const real ratioW);
+
 /**
  * @brief   MaxOut forward.
  *

paddle/cuda/include/stub/hl_cnn_stub.h

@@ -89,6 +89,34 @@ inline void hl_CMRNorm_backward(
     size_t channels, size_t height, size_t width, size_t sizeX,
     real alpha, real beta) {}
 
+inline void hl_bilinear_forward(const real* inData,
+                                const size_t inImgH,
+                                const size_t inImgW,
+                                const size_t inputH,
+                                const size_t inputW,
+                                real* outData,
+                                const size_t outImgH,
+                                const size_t outImgW,
+                                const size_t outputH,
+                                const size_t outputW,
+                                const size_t numChannels,
+                                const real ratioH,
+                                const real ratioW) {}
+
+inline void hl_bilinear_backward(real* inGrad,
+                                const size_t inImgH,
+                                const size_t inImgW,
+                                const size_t inputH,
+                                const size_t inputW,
+                                const real* outGrad,
+                                const size_t outImgH,
+                                const size_t outImgW,
+                                const size_t outputH,
+                                const size_t outputW,
+                                const size_t numChannels,
+                                const real ratioH,
+                                const real ratioW) {}
+
 inline void hl_maxout_forward(
     const real* inData, real* outData, int* idData,
     size_t batchSize, size_t size, size_t featLen, size_t group) {}

paddle/cuda/src/hl_cuda_cnn.cu

@@ -522,7 +522,7 @@ void hl_CMRNorm_backward(size_t frameCnt, const real* inV,
                          size_t height, size_t width, size_t sizeX,
                          real alpha, real beta) {
   size_t threadsNum = frameCnt * height * width;
-  size_t blocksX = (threadsNum + 1024 -1) / 1024;
+  size_t blocksX = (threadsNum + 1024 - 1) / 1024;
   size_t blocksY = 1;
   dim3 threads(1024, 1);
   dim3 grid(blocksX, blocksY);
@@ -532,6 +532,138 @@ void hl_CMRNorm_backward(size_t frameCnt, const real* inV,
   CHECK_SYNC("hl_CMRNorm_backward");
 }
 
+__global__ void KeBilinearInterpFw(const real* in,
+                                   const size_t inImgH,
+                                   const size_t inImgW,
+                                   const size_t inputH,
+                                   const size_t inputW,
+                                   real* out,
+                                   const size_t outImgH,
+                                   const size_t outImgW,
+                                   const size_t outputH,
+                                   const size_t outputW,
+                                   const size_t numChannels,
+                                   const real ratioH,
+                                   const real ratioW) {
+  int nthreads = outputH * outputW;                      
+  int tid = blockIdx.x * blockDim.x + threadIdx.x;
+  if (tid < nthreads) {
+    int outIdH = tid / outputW;
+    int outIdW = tid % outputW;
+    int inImgSize = inputW / numChannels;
+    int outImgSize = outputW / numChannels;
+    int channelId = outIdW / outImgSize;
+
+    int outImgIdy = (outIdW % outImgSize) / outImgW;
+    int inImgIdy = ratioH * outImgIdy;
+    int hId = (inImgIdy < inImgH - 1) ? 1 : 0;
+    real h1lambda = ratioH * outImgIdy - inImgIdy;
+    real h2lambda = 1.f - h1lambda;
+
+    int outImgIdx = tid % outImgW;
+    int inImgIdx = ratioW * outImgIdx;
+    int wId = (inImgIdx < inImgW - 1) ? 1 : 0;
+    real w1lambda = ratioW * outImgIdx - inImgIdx;
+    real w2lambda = 1.f - w1lambda;
+
+    const real* inPos =
+      &in[outIdH * inputW + channelId * inImgSize + inImgIdy * inImgW + inImgIdx];
+
+    // bilinear interpolation
+    out[outIdH * outputW + outIdW] =
+      h2lambda * (w2lambda * inPos[0]            + w1lambda * inPos[wId]) + 
+      h1lambda * (w2lambda * inPos[hId * inImgW] + w1lambda * inPos[hId * inImgW + wId]);
+  }
+}
+
+void hl_bilinear_forward(const real* inData,
+                         const size_t inImgH,
+                         const size_t inImgW,
+                         const size_t inputH,
+                         const size_t inputW,
+                         real* outData,
+                         const size_t outImgH,
+                         const size_t outImgW,
+                         const size_t outputH,
+                         const size_t outputW,
+                         const size_t numChannels,
+                         const real ratioH,
+                         const real ratioW) {
+  int threadNum = outputH * outputW;
+  int blocks = (threadNum + 1024 - 1) / 1024;
+
+  KeBilinearInterpFw<<< blocks, 1024, 0, STREAM_DEFAULT>>>(
+    inData, inImgH, inImgW, inputH, inputW, outData, outImgH,
+    outImgW, outputH, outputW, numChannels, ratioH, ratioW);
+  CHECK_SYNC("hl_bilinear_forward failed");
+}
+
+__global__ void KeBilinearInterpBw(real* in,
+                                   const size_t inImgH,
+                                   const size_t inImgW,
+                                   const size_t inputH,
+                                   const size_t inputW,
+                                   const real* out,
+                                   const size_t outImgH,
+                                   const size_t outImgW,
+                                   const size_t outputH,
+                                   const size_t outputW,
+                                   const size_t numChannels,
+                                   const real ratioH,
+                                   const real ratioW) {
+  int nthreads = outputH * outputW;
+  int tid = blockIdx.x * blockDim.x + threadIdx.x;
+  if (tid < nthreads) {
+    int outIdH = tid / outputW;
+    int outIdW = tid % outputW;
+    int inImgSize = inputW / numChannels;
+    int outImgSize = outputW / numChannels;
+    int channelId = outIdW / outImgSize;
+
+    int outImgIdy = (outIdW % outImgSize) / outImgW;
+    int inImgIdy = ratioH * outImgIdy;
+    int hId = (inImgIdy < inImgH - 1) ? 1 : 0;
+    real h1lambda = ratioH * outImgIdy - inImgIdy;
+    real h2lambda = 1.f - h1lambda;
+
+    int outImgIdx = tid % outImgW;
+    int inImgIdx = ratioW * outImgIdx;
+    int wId = (inImgIdx < inImgW - 1) ? 1 : 0;
+    real w1lambda = ratioW * outImgIdx - inImgIdx;
+    real w2lambda = 1.f - w1lambda;
+
+    real* inPos =
+      &in[outIdH * inputW + channelId * inImgSize + inImgIdy * inImgW + inImgIdx];
+    const real* outPos = &out[outIdH * outputW + outIdW];
+    atomicAdd(&inPos[0], h2lambda * w2lambda * outPos[0]);
+    atomicAdd(&inPos[wId], h2lambda * w1lambda * outPos[0]);
+    atomicAdd(&inPos[hId * inImgW], h1lambda * w2lambda * outPos[0]);
+    atomicAdd(&inPos[hId * inImgW + wId], h1lambda * w1lambda * outPos[0]);
+  }
+}
+
+void hl_bilinear_backward(real* inGrad,
+                          const size_t inImgH,
+                          const size_t inImgW,
+                          const size_t inputH,
+                          const size_t inputW,
+                          const real* outGrad,
+                          const size_t outImgH,
+                          const size_t outImgW,
+                          const size_t outputH,
+                          const size_t outputW,
+                          const size_t numChannels,
+                          const real ratioH,
+                          const real ratioW) {
+  int threadNum = outputH * outputW;
+  int blocks = (threadNum + 1024 - 1) / 1024;
+
+  KeBilinearInterpBw<<< blocks, 1024, 0, STREAM_DEFAULT>>>(
+    inGrad, inImgH, inImgW, inputH, inputW, outGrad, outImgH,
+    outImgW, outputH, outputW, numChannels, ratioH, ratioW);
+  CHECK_SYNC("hl_bilinear_backward failed");
+}
+
 __global__ void maxoutFpCompute(size_t nthreads, const real * inData,
                                 real * outData, int* idData, 
                                 size_t size, size_t featLen, size_t groups) {

paddle/gserver/layers/BilinearInterpLayer.cpp

+/* Copyright (c) 2016 Baidu, Inc. All Rights Reserve.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License. */
+
+#include "BilinearInterpLayer.h"
+#include "paddle/utils/Logging.h"
+#include "paddle/utils/Stat.h"
+
+namespace paddle {
+
+REGISTER_LAYER(bilinear_interp, BilinearInterpLayer);
+
+size_t BilinearInterpLayer::getSize() {
+  inImgH_ = inputLayers_[0]->getOutput().getFrameHeight();
+  inImgW_ = inputLayers_[0]->getOutput().getFrameWidth();
+
+  const BilinearInterpConfig& conf = config_.inputs(0).bilinear_interp_conf();
+  if (inImgH_ == 0) {
+    inImgH_ = conf.img_size_y();
+  }
+  if (inImgW_ == 0) {
+    inImgW_ = conf.img_size_x();
+  }
+
+  outImgH_ = conf.out_size_y();
+  outImgW_ = conf.out_size_x();
+  numChannels_ = conf.num_channels();
+
+  CHECK(outImgH_ > 0 && outImgW_ > 0);
+  CHECK(inImgH_ > 0 && inImgW_ > 0);
+  CHECK(numChannels_);
+
+  ratioH_ = (outImgH_ > 1) ?
+    static_cast<real>(inImgH_ - 1) / (outImgH_ - 1) : 0.f;
+  ratioW_ = (outImgW_ > 1) ?
+    static_cast<real>(inImgW_ - 1) / (outImgW_ - 1) : 0.f;
+
+  getOutput().setFrameHeight(outImgH_);
+  getOutput().setFrameWidth(outImgW_);
+  return outImgH_ * outImgW_ * numChannels_;
+}
+
+bool BilinearInterpLayer::init(const LayerMap& layerMap,
+                               const ParameterMap& parameterMap) {
+  /* Initialize the basic parent class */
+  Layer::init(layerMap, parameterMap);
+
+  CHECK_EQ(1, config_.inputs_size());
+
+  return true;
+}
+
+void BilinearInterpLayer::forward(PassType passType) {
+  Layer::forward(passType);
+
+  size_t batchSize = getInput(0).getBatchSize();
+  size_t size = getSize();
+  {
+    REGISTER_TIMER_INFO("FwResetTimer", getName().c_str());
+    resetOutput(batchSize, size);
+  }
+
+  MatrixPtr inV = getInputValue(0);
+  MatrixPtr outV = getOutputValue();
+  {
+    REGISTER_TIMER_INFO("FwBilinearInterpTimer", getName().c_str());
+    outV->bilinearForward(*inV, inImgH_, inImgW_, outImgH_, outImgW_,
+      numChannels_, ratioH_, ratioW_);
+  }
+}
+
+void BilinearInterpLayer::backward(const UpdateCallback& callback) {
+  (void) callback;
+
+  MatrixPtr inputG = getInputGrad(0);
+  MatrixPtr outG = getOutputGrad();
+  {
+    REGISTER_TIMER_INFO("BwBilinearInterpTimer", getName().c_str());
+    if (inputG) {
+      inputG->bilinearBackward(*outG, outImgH_, outImgW_, inImgH_, inImgW_,
+        numChannels_, ratioH_, ratioW_);
+    }
+  }
+}
+}  // namespace paddle

paddle/gserver/layers/BilinearInterpLayer.h

+/* Copyright (c) 2016 Baidu, Inc. All Rights Reserve.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License. */
+
+#pragma once
+
+#include "Layer.h"
+#include "paddle/math/Matrix.h"
+
+namespace paddle {
+
+/**
+ * @brief A layer for bilinear interpolation which is
+ *        used on conv layer output.
+ *
+ * @note  The config file api is bilinear_interp_layer.
+ */
+class BilinearInterpLayer : public Layer {
+protected:
+  size_t outImgH_, outImgW_;
+  size_t inImgH_, inImgW_;
+  real ratioH_, ratioW_;
+  size_t numChannels_;
+
+public:
+  explicit BilinearInterpLayer(const LayerConfig& config) : Layer(config) {}
+
+  virtual ~BilinearInterpLayer() {}
+
+  size_t getSize();
+  bool init(const LayerMap& layerMap, const ParameterMap& parameterMap);
+  void forward(PassType passType);
+  void backward(const UpdateCallback& callback = nullptr);
+};
+
+}  // namespace paddle

paddle/gserver/tests/test_LayerGrad.cpp

@@ -175,6 +175,27 @@ TEST(Projection, conv) {
 }
 #endif
 
+TEST(Layer, BilinearInterpLayer) {
+  TestConfig config;
+  config.layerConfig.set_type("bilinear_interp");
+  config.biasSize = 0;
+  config.inputDefs.push_back({INPUT_DATA, "layer_0", 4096, 0});
+
+  LayerInputConfig* input = config.layerConfig.add_inputs();
+  BilinearInterpConfig* bilinear = input->mutable_bilinear_interp_conf();
+  bilinear->set_img_size_x(32);
+  bilinear->set_img_size_y(32);
+  bilinear->set_num_channels(4);
+
+  for (auto useGpu : {false, true}) {
+    for (auto outSize : {32, 64}) {
+      bilinear->set_out_size_x(outSize);
+      bilinear->set_out_size_y(outSize);
+      testLayerGrad(config, "bilinear_interp", 10, false, useGpu);
+    }
+  }
+}
+
 TEST(Layer, concat) {
   TestConfig config;
   config.biasSize = 0;

paddle/math/Matrix.cpp

@@ -23,6 +23,7 @@ limitations under the License. */
 
 #include "paddle/utils/Logging.h"
 #include <string.h>
+#include "hl_cnn.h"
 #include "hl_gpu.h"
 #include "hl_table_apply.h"
 #include "hl_top_k.h"
@@ -1231,6 +1232,62 @@ void GpuMatrix::addColumnVector(const Matrix& b) {
   BaseMatrix::addColVector(const_cast<Matrix&>(b));
 }
 
+void GpuMatrix::bilinearForward(const Matrix& in,
+                                const size_t inImgH,
+                                const size_t inImgW,
+                                const size_t outImgH,
+                                const size_t outImgW,
+                                const size_t numChannels,
+                                const real ratioH,
+                                const real ratioW) {
+  CHECK(dynamic_cast<const GpuMatrix*>(&in));
+
+  const size_t outputW = getWidth();
+  const size_t outputH = getHeight();
+  const size_t inputW = in.getWidth();
+  const size_t inputH = in.getHeight();
+
+  real* outData = getData();
+  const real* inData  = in.getData();
+
+  if (inImgH == outImgW && inImgW == outImgW) {
+    this->copyFrom(in);
+  } else {
+    hl_bilinear_forward(
+      inData, inImgH, inImgW, inputH, inputW, outData,
+      outImgH, outImgW, outputH, outputW, numChannels,
+      ratioH, ratioW);
+  }
+}
+
+void GpuMatrix::bilinearBackward(const Matrix& out,
+                                 const size_t outImgH,
+                                 const size_t outImgW,
+                                 const size_t inImgH,
+                                 const size_t inImgW,
+                                 const size_t numChannels,
+                                 const real ratioH,
+                                 const real ratioW) {
+  CHECK(dynamic_cast<const GpuMatrix*>(&out));
+
+  const size_t inputW = getWidth();
+  const size_t inputH = getHeight();
+  const size_t outputW = out.getWidth();
+  const size_t outputH = out.getHeight();
+
+  real* inGrad = getData();
+  const real* outGrad = out.getData();
+
+  if (outImgH == inImgH && outImgW == inImgW) {
+    this->add(const_cast<Matrix&>(out));
+  } else {
+    hl_bilinear_backward(
+      inGrad, inImgH, inImgW, inputH, inputW, outGrad,
+      outImgH, outImgW, outputH, outputW, numChannels,
+      ratioH, ratioW);
+  }
+}
+
 /**
  * CpuMatrix
  */
@@ -3841,6 +3898,112 @@ void CpuMatrix::classificationErrorMulti(Matrix& output, Matrix& label,
   }
 }
 
+void CpuMatrix::bilinearForward(const Matrix& in,
+                                const size_t inImgH,
+                                const size_t inImgW,
+                                const size_t outImgH,
+                                const size_t outImgW,
+                                const size_t numChannels,
+                                const real ratioH,
+                                const real ratioW) {
+  CHECK(dynamic_cast<const CpuMatrix*>(&in));
+
+  size_t outputW = getWidth();
+  size_t batchSize = getHeight();
+  size_t inputW = in.getWidth();
+  size_t inputH = in.getHeight();
+  size_t inPosOffset = inImgH * inImgW;
+  size_t outPosOffset = outImgH * outImgW;
+  (void)(inputH);
+
+  real* outData = getData();
+  const real* inData  = in.getData();
+
+  if (inImgH == outImgH && inImgW == outImgW) {
+    this->copyFrom(in);
+  } else {
+    for (size_t k = 0; k < batchSize; ++k) {   // loop for batches
+      for (size_t i = 0; i < outImgH; ++i) {  // loop for images
+        size_t h = ratioH * i;
+        size_t hid = (h < inImgH - 1) ? 1 : 0;
+        real h1lambda = ratioH * i - h;
+        real h2lambda = 1 - h1lambda;
+
+        for (size_t j = 0; j < outImgW; ++j) {
+          size_t w = ratioW * j;
+          size_t wid = (w < inImgW - 1) ? 1 : 0;
+          real w1lambda = ratioW * j - w;
+          real w2lambda = 1 - w1lambda;
+          // calculate four position for bilinear interpolation
+          const real* inPos = &inData[k * inputW + h * inImgW + w];
+          real* outPos = &outData[k * outputW + i * outImgW + j];
+          for (size_t c = 0; c < numChannels; ++c) {  // loop for channels
+            // bilinear interpolation
+            outPos[0] =
+              h2lambda * (w2lambda * inPos[0] + w1lambda * inPos[wid]) +
+              h1lambda * (w2lambda * inPos[hid * inImgW] +
+              w1lambda * inPos[hid * inImgW + wid]);
+            inPos += inPosOffset;
+            outPos += outPosOffset;
+          }
+        }
+      }
+    }
+  }
+}
+
+void CpuMatrix::bilinearBackward(const Matrix& out,
+                                 const size_t outImgH,
+                                 const size_t outImgW,
+                                 const size_t inImgH,
+                                 const size_t inImgW,
+                                 const size_t numChannels,
+                                 const real ratioH,
+                                 const real ratioW) {
+  CHECK(dynamic_cast<const CpuMatrix*>(&out));
+
+  size_t inputW = getWidth();
+  size_t inputH = getHeight();
+  size_t outputW = out.getWidth();
+  size_t batchSize = out.getHeight();
+  size_t inPosOffset = inImgH * inImgW;
+  size_t outPosOffset = outImgH * outImgW;
+  (void)(inputH);
+
+  real* inGrad = getData();
+  const real* outGrad = out.getData();
+
+  if (inImgH == outImgH && inImgW == outImgW) {
+    this->add(const_cast<Matrix&>(out));
+  } else {
+    for (size_t k = 0; k < batchSize; ++k) {   // loop for batches
+      for (size_t i = 0; i < outImgH; ++i) {  // loop for images
+        size_t h = ratioH * i;
+        size_t hid = (h < inImgH - 1) ? 1 : 0;
+        real h1lambda = ratioH * i - h;
+        real h2lambda = 1 - h1lambda;
+        for (size_t j = 0; j < outImgW; ++j) {
+          size_t w = ratioW * j;
+          size_t wid = (w < inImgW - 1) ? 1 : 0;
+          real w1lambda = ratioW * j - w;
+          real w2lambda = 1 - w1lambda;
+
+          real* inPos = &inGrad[k * inputW + h * inImgW + w];
+          const real* outPos = &outGrad[k * outputW + i * outImgW + j];
+          for (size_t c = 0; c < numChannels; ++c) {  // loop for channels
+            inPos[0] += h2lambda * w2lambda * outPos[0];
+            inPos[wid] += h2lambda * w1lambda * outPos[0];
+            inPos[hid * inImgW] += h1lambda * w2lambda * outPos[0];
+            inPos[hid * inImgW + wid] += h1lambda * w1lambda * outPos[0];
+            inPos += inPosOffset;
+            outPos += outPosOffset;
+          }
+        }
+      }
+    }
+  }
+}
+
 ////////////////////////////////////////////////////////////////
 //               functions executed via cpu                   //
 ////////////////////////////////////////////////////////////////

paddle/math/Matrix.h

@@ -995,6 +995,26 @@ public:
   virtual void paramReluBackwardDiff(Matrix& oGrad, Matrix& data, Matrix& W) {
     LOG(FATAL) << "Not implemented";
   }
+  virtual void bilinearForward(const Matrix& in,
+                               const size_t inImgH,
+                               const size_t inImgW,
+                               const size_t outImgH,
+                               const size_t outImgW,
+                               const size_t numChannels,
+                               const real ratioH,
+                               const real ratioW) {
+    LOG(FATAL) << "Not implemented";
+  }
+  virtual void bilinearBackward(const Matrix& out,
+                                const size_t outImgH,
+                                const size_t outImgW,
+                                const size_t inImgH,
+                                const size_t inImgW,
+                                const size_t numChannels,
+                                const real ratioH,
+                                const real ratioW) {
+    LOG(FATAL) << "Not implemented";
+  }
 };
 
 inline std::ostream& operator<<(std::ostream& os, const Matrix& mat) {
@@ -1265,6 +1285,24 @@ public:
                                        int contextLength,
                                        int contextStart, int totalPad,
                                        size_t beginPad);
+
+  void bilinearForward(const Matrix& in,
+                       const size_t inImgH,
+                       const size_t inImgW,
+                       const size_t outImgH,
+                       const size_t outImgW,
+                       const size_t numChannels,
+                       const real ratioH,
+                       const real ratioW);
+
+  void bilinearBackward(const Matrix& out,
+                        const size_t outImgH,
+                        const size_t outImgW,
+                        const size_t inImgH,
+                        const size_t inImgW,
+                        const size_t numChannels,
+                        const real ratioH,
+                        const real ratioW);
 };
 
 class CpuMatrix : public Matrix {
@@ -1553,6 +1591,24 @@ public:
   void multiBinaryLabelCrossEntropy(Matrix& output, Matrix& label);
   void multiBinaryLabelCrossEntropyBp(Matrix& output, Matrix& label);
   void classificationErrorMulti(Matrix& output, Matrix& label, real threshold);
+
+  void bilinearForward(const Matrix& in,
+                       const size_t inImgH,
+                       const size_t inImgW,
+                       const size_t outImgH,
+                       const size_t outImgW,
+                       const size_t numChannels,
+                       const real ratioH,
+                       const real ratioW);
+
+  void bilinearBackward(const Matrix& out,
+                        const size_t outImgH,
+                        const size_t outImgW,
+                        const size_t inImgH,
+                        const size_t inImgW,
+                        const size_t numChannels,
+                        const real ratioH,
+                        const real ratioW);
 };
 
 class SharedCpuMatrix : public CpuMatrix {

paddle/math/tests/test_matrixCompare.cpp

@@ -90,6 +90,73 @@ void MatrixCheckErr(const Matrix& matrix1, const Matrix& matrix2) {
   EXPECT_EQ(count, 0) << "There are " << count << " different element.";
 }
 
+void testBilinearFwdBwd(int numSamples, int imgSizeH, int imgSizeW,
+                        int channels) {
+  int inWidth = imgSizeH * imgSizeW * channels;
+  int outWidth = 2 * imgSizeH * 2 * imgSizeW * channels;
+  real ratioH = 0.5;
+  real ratioW = 0.5;
+  // forward
+  MatrixPtr input = CpuMatrix::create(numSamples, inWidth, false, false);
+  MatrixPtr inputGpu = GpuMatrix::create(numSamples, inWidth, false, true);
+
+  MatrixPtr target = CpuMatrix::create(numSamples, outWidth, false, false);
+  MatrixPtr targetGpu = GpuMatrix::create(numSamples, outWidth, false, true);
+  MatrixPtr targetCheck = CpuMatrix::create(numSamples, outWidth, false, false);
+
+  input->randomizeUniform();
+  inputGpu->copyFrom(*input);
+
+  target->bilinearForward(*input, imgSizeH, imgSizeW,
+      2 * imgSizeH, 2 * imgSizeW, channels, ratioH, ratioW);
+  targetGpu->bilinearForward(*inputGpu, imgSizeH, imgSizeW,
+      2 * imgSizeH, 2 * imgSizeW, channels, ratioH, ratioW);
+
+  // check
+  targetCheck->copyFrom(*targetGpu);
+  MatrixCheckErr(*target, *targetCheck);
+
+  // backward
+  MatrixPtr inputGrad = CpuMatrix::create(numSamples, inWidth, false, false);
+  MatrixPtr inputGpuGrad = GpuMatrix::create(numSamples, inWidth, false, true);
+
+  MatrixPtr targetGrad = CpuMatrix::create(numSamples, outWidth, false, false);
+  MatrixPtr targetGpuGrad = GpuMatrix::create(numSamples, outWidth, false,
+                                              true);
+  MatrixPtr targetCheckGrad =
+      CpuMatrix::create(numSamples, inWidth, false, false);
+
+  inputGrad->randomizeUniform();
+  targetGrad->randomizeUniform();
+  inputGpuGrad->copyFrom(*inputGrad);
+  targetGpuGrad->copyFrom(*targetGrad);
+
+  inputGrad->bilinearBackward(*targetGrad, 2 * imgSizeH, 2 * imgSizeW,
+      imgSizeH, imgSizeW, channels, ratioH, ratioW);
+  inputGpuGrad->bilinearBackward(*targetGpuGrad, 2 * imgSizeH, 2 * imgSizeW,
+      imgSizeH, imgSizeW, channels, ratioH, ratioW);
+
+  // check
+  targetCheckGrad->copyFrom(*inputGpuGrad);
+  MatrixCheckErr(*inputGrad, *targetCheckGrad);
+}
+
+TEST(Matrix, BilinearFwdBwd) {
+  for (auto numSamples : {5, 10}) {
+    for (auto channels : {8, 16}) {
+      for (auto imgSizeH : {14, 28}) {
+        for (auto imgSizeW : {16, 30}) {
+          VLOG(3) << " numSamples=" << numSamples
+                  << " channels=" << channels
+                  << " imgSizeH=" << imgSizeH
+                  << " imgSizeW=" << imgSizeW;
+          testBilinearFwdBwd(numSamples, imgSizeH, imgSizeW, channels);
+        }
+      }
+    }
+  }
+}
+
 void testMatrixProjectionForward(int contextStart, int contextLength,
                                  bool padding, int batchSize, int inputDim) {
   MatrixPtr cpuInput = std::make_shared<CpuMatrix>(batchSize, inputDim);

proto/ModelConfig.proto.m4

@@ -212,6 +212,15 @@ message OperatorConfig {
   optional int32 num_filters = 7;
 }
 
+message BilinearInterpConfig {
+  // The size of input feature map.
+  optional uint32 img_size_x = 1;
+  optional uint32 img_size_y = 2;
+  // The size of output feature map.
+  required uint32 out_size_x = 3;
+  required uint32 out_size_y = 4;
+  required uint32 num_channels = 5;
+}
 
 message ImageConfig {
   // The image data dimensionality.
@@ -234,7 +243,8 @@ message LayerInputConfig {
   // If the input layer has multi-output.
   // Set the argument name.
   optional string input_layer_argument = 9;
-  optional MaxOutConfig maxout_conf = 10;
+  optional BilinearInterpConfig bilinear_interp_conf = 10;
+  optional MaxOutConfig maxout_conf = 11;
 }
 
 message LayerConfig {

python/paddle/trainer/config_parser.py

@@ -465,6 +465,7 @@ class Input(Cfg):
             sparse_update=None,
             gradient_clipping_threshold=None,
             conv=None,
+            bilinear_interp=None,
             norm=None,
             pool=None,
             image=None,
@@ -768,6 +769,16 @@ class Conv(Cfg):
         if output_x is not None:
           config_assert(output_x <= 0)
 
+# please refer to the comments in proto/ModelConfig.proto
+@config_class
+class BilinearInterp(Cfg):
+    def __init__(
+            self,
+            out_size_x = None,
+            out_size_y = None,
+            num_channels = None):
+        self.add_keys(locals())
+
 # please refer to the comments in proto/ModelConfig.proto
 @config_class
 class Pool(Cfg):
@@ -1008,6 +1019,11 @@ def TestData(data_config, async_load_data=None):
                        " Data definition")
         g_config.test_data_config.async_load_data = async_load_data
 
+def parse_bilinear(bilinear, input_layer_name, bilinear_conf):
+    bilinear_conf.out_size_x = bilinear.out_size_x;
+    bilinear_conf.out_size_y = bilinear.out_size_y;
+    bilinear_conf.num_channels = bilinear.num_channels;
+
 '''
 caffe_mode: compute the output size using floor instead of ceil,
             which is consistent of caffe and CuDNN's convention.
@@ -2470,6 +2486,22 @@ class InterpolationLayer(LayerBase):
         config_assert(input_layer1.size == input_layer2.size,
                       'the two vector inputs should be of the same size')
 
+@config_layer('bilinear_interp')
+class BilinearInterpLayer(LayerBase):
+    def __init__(
+            self,
+            name,
+            inputs,
+            **xargs):
+        super(BilinearInterpLayer, self).__init__(
+            name, 'bilinear_interp', 0, inputs=inputs, **xargs)
+        input_layer = self.get_input_layer(0)
+        parse_bilinear(self.inputs[0].bilinear_interp,
+                       input_layer.name,
+                       self.config.inputs[0].bilinear_interp_conf);
+        conf = self.inputs[0].bilinear_interp
+        self.set_layer_size(conf.out_size_x * conf.out_size_y *  conf.num_channels)
+
 @config_layer('sum_to_one_norm')
 class SumToOneNormLayer(LayerBase):
     def __init__(

python/paddle/trainer_config_helpers/layers.py

@@ -40,8 +40,8 @@ __all__ = ["full_matrix_projection", "AggregateLevel", "ExpandLevel",
            'img_cmrnorm_layer', 'addto_layer',
            'concat_layer', 'lstm_step_layer', 'recurrent_group',
            'memory', 'StaticInput', 'expand_layer', 'scaling_layer',
-           'power_layer', 'interpolation_layer', 'trans_layer',
-           'sum_to_one_norm_layer',
+           'power_layer', 'interpolation_layer', 'bilinear_interp_layer',
+           'trans_layer', 'sum_to_one_norm_layer',
            'get_output_layer', 'LayerType', 'context_projection',
            'beam_search', 'maxid_layer', 'GeneratedInput', 'SubsequenceInput',
            'gru_step_layer', 'recurrent_layer',
@@ -94,6 +94,7 @@ class LayerType(object):
 
     EXPAND_LAYER = 'expand'
     INTERPOLATION_LAYER = 'interpolation'
+    BILINEAR_INTERP_LAYER = 'bilinear_interp'
     POWER_LAYER = 'power'
     SCALING_LAYER = 'scaling'
     TRANS_LAYER = 'trans'
@@ -1259,6 +1260,52 @@ def interpolation_layer(input, weight, name=None, layer_attr=None):
                        size=input[0].size)
 
 
+@wrap_name_default()
+@layer_support()
+def bilinear_interp_layer(input,
+                          out_size_x=None,
+                          out_size_y=None,
+                          name=None,
+                          layer_attr=None):
+    """
+    This layer is to implement bilinear interpolation on conv layer output.
+
+    Please refer to Wikipedia: https://en.wikipedia.org/wiki/Bilinear_interpolation
+
+    The simple usage is:
+
+    .. code-block:: python
+
+       bilinear = bilinear_interp_layer(input=layer1, out_size_x=64, out_size_y=64)
+    
+    :param   input:        A input layer.
+    :type    input:        LayerOutput.
+    :param   out_size_x:   bilinear interpolation output width.
+    :type    out_size_x:   int|None 
+    :param   out_size_y:   bilinear interpolation output height.
+    :type    out_size_y:   int|None
+    :param   name:         The layer's name, which cna not be specified.
+    :type    name:         None|basestring
+    :param   layer_attr:   Extra Layer attribute.
+    :type    layer_attr:   ExtraLayerAttribute
+    :return: LayerOutput object.
+    :rtype:  LayerOutput
+    """
+    assert input.layer_type == LayerType.CONV_LAYER
+    assert isinstance(input.activation, LinearActivation)
+    assert out_size_x > 0 and out_size_y > 0
+    assert input.num_filters is not None
+    num_channels = input.num_filters
+    Layer(name=name,
+          inputs=Input(input.name,
+                       bilinear_interp=BilinearInterp(out_size_x=out_size_x,
+                                                      out_size_y=out_size_y,
+                                                      num_channels=num_channels)),
+          type=LayerType.BILINEAR_INTERP_LAYER,
+          **ExtraLayerAttribute.to_kwargs(layer_attr))
+    return LayerOutput(name, LayerType.BILINEAR_INTERP_LAYER, parents=[input],
+           num_filters=num_channels)
+
 @wrap_name_default()
 @layer_support()
 def power_layer(input, weight, name=None, layer_attr=None):

python/paddle/trainer_config_helpers/tests/configs/generate_protostr.sh

@@ -11,7 +11,7 @@ test_sequence_pooling test_lstmemory_layer test_grumemory_layer
 last_first_seq test_expand_layer test_ntm_layers test_hsigmoid
 img_layers img_trans_layers util_layers simple_rnn_layers unused_layers test_cost_layers
 test_rnn_group shared_fc shared_lstm test_cost_layers_with_weight
-test_maxout test_bi_grumemory math_ops)
+test_bilinear_interp test_maxout test_bi_grumemory math_ops)
 
 
 for conf in ${configs[*]}

python/paddle/trainer_config_helpers/tests/configs/protostr/test_bilinear_interp.protostr

+type: "nn"
+layers {
+  name: "data"
+  type: "data"
+  size: 2304
+  active_type: ""
+}
+layers {
+  name: "__conv_0__"
+  type: "exconv"
+  size: 36864
+  active_type: ""
+  inputs {
+    input_layer_name: "data"
+    input_parameter_name: "___conv_0__.w0"
+    conv_conf {
+      filter_size: 3
+      channels: 1
+      stride: 1
+      padding: 1
+      groups: 1
+      filter_channels: 1
+      output_x: 48
+      img_size: 48
+      caffe_mode: true
+      filter_size_y: 3
+      padding_y: 1
+      stride_y: 1
+    }
+  }
+  bias_parameter_name: "___conv_0__.wbias"
+  num_filters: 16
+  shared_biases: true
+}
+layers {
+  name: "__bilinear_interp_layer_0__"
+  type: "bilinear_interp"
+  size: 65536
+  active_type: ""
+  inputs {
+    input_layer_name: "__conv_0__"
+    bilinear_interp_conf {
+      out_size_x: 64
+      out_size_y: 64
+      num_channels: 16
+    }
+  }
+}
+layers {
+  name: "__pool_0__"
+  type: "pool"
+  size: 16384
+  active_type: ""
+  inputs {
+    input_layer_name: "__bilinear_interp_layer_0__"
+    pool_conf {
+      pool_type: "max-projection"
+      channels: 4
+      size_x: 2
+      stride: 2
+      output_x: 64
+      img_size: 128
+      padding: 0
+      size_y: 2
+      stride_y: 2
+      output_y: 64
+      img_size_y: 128
+      padding_y: 0
+    }
+  }
+}
+layers {
+  name: "__fc_layer_0__"
+  type: "fc"
+  size: 384
+  active_type: "tanh"
+  inputs {
+    input_layer_name: "__pool_0__"
+    input_parameter_name: "___fc_layer_0__.w0"
+  }
+}
+parameters {
+  name: "___conv_0__.w0"
+  size: 144
+  initial_mean: 0.0
+  initial_std: 0.471404520791
+  initial_strategy: 0
+  initial_smart: false
+}
+parameters {
+  name: "___conv_0__.wbias"
+  size: 16
+  initial_mean: 0.0
+  initial_std: 0.0
+  dims: 16
+  dims: 1
+  initial_strategy: 0
+  initial_smart: false
+}
+parameters {
+  name: "___fc_layer_0__.w0"
+  size: 6291456
+  initial_mean: 0.0
+  initial_std: 0.0078125
+  dims: 16384
+  dims: 384
+  initial_strategy: 0
+  initial_smart: true
+}
+input_layer_names: "data"
+output_layer_names: "__fc_layer_0__"
+sub_models {
+  name: "root"
+  layer_names: "data"
+  layer_names: "__conv_0__"
+  layer_names: "__bilinear_interp_layer_0__"
+  layer_names: "__pool_0__"
+  layer_names: "__fc_layer_0__"
+  input_layer_names: "data"
+  output_layer_names: "__fc_layer_0__"
+  is_recurrent_layer_group: false
+}
+

python/paddle/trainer_config_helpers/tests/configs/test_bilinear_interp.py

+from paddle.trainer_config_helpers import *
+
+settings(
+    batch_size=1000,
+    learning_rate=1e-5
+)
+
+data = data_layer(name='data', size=2304)
+
+conv = img_conv_layer(input=data,
+                      filter_size = 3,
+                      num_channels=1,
+                      num_filters=16,
+                      padding=1,
+                      act=LinearActivation(),
+                      bias_attr=True)
+
+bilinear = bilinear_interp_layer(input=conv,
+                                 out_size_x=64,
+                                 out_size_y=64)
+
+pool = img_pool_layer(input=bilinear,
+                      num_channels=4,
+                      pool_size=2,
+                      stride=2,
+                      pool_type=MaxPooling())
+
+fc = fc_layer(input=pool, size=384, bias_attr=False)
+
+outputs(fc)
\ No newline at end of file