From fb46345f007e7c989d8c5d635dc0ff9d24bbbf31 Mon Sep 17 00:00:00 2001
From: hedaoyuan <hedaoyuan@github.com>
Date: Wed, 13 Sep 2017 14:15:58 +0800
Subject: [PATCH] Add groups in convolution operator.

---
 paddle/operators/conv_op.cc     | 22 ++++++++++++++++++--
 paddle/operators/gemm_conv_op.h | 36 ++++++++++++++++++++++-----------
 2 files changed, 44 insertions(+), 14 deletions(-)

diff --git a/paddle/operators/conv_op.cc b/paddle/operators/conv_op.cc
index 107682848b..174f777f0e 100644
--- a/paddle/operators/conv_op.cc
+++ b/paddle/operators/conv_op.cc
@@ -31,12 +31,22 @@ class Conv2DOp : public framework::OperatorWithKernel {
     auto in = ctx.Input<Tensor>("Input");
     auto filter = ctx.Input<Tensor>("Filter");
     auto out = ctx.Output<Tensor>("Output");
+    std::vector<int> strides = Attr<std::vector<int>>("strides");
+    std::vector<int> paddings = Attr<std::vector<int>>("paddings");
+    int groups = context.Attr<int>("groups");
+    int input_channels = in->dims()[1];
+    int output_channels = filter->dims()[0];
+
     PADDLE_ENFORCE_EQ(in->dims().size(), 4, "Conv2DOp intput should be 4-D.");
     PADDLE_ENFORCE_EQ(filter->dims().size(), 4,
                       "Conv2DOp filter should be 4-D.");
+    PADDLE_ENFORCE_EQ(input_channels, filter->dims()[1] * groups,
+                      "The number of input channels should be equal to filter "
+                      "channels * groups.");
+    PADDLE_ENFORCE_EQ(
+        output_channels % groups, 0,
+        "The number of output channels should be divided by groups.");
 
-    std::vector<int> strides = Attr<std::vector<int>>("strides");
-    std::vector<int> paddings = Attr<std::vector<int>>("paddings");
     auto output_height =
         outputSize(in->dims()[2], filter->dims()[2], paddings[0], strides[0]);
     auto output_width =
@@ -71,6 +81,14 @@ the input, filter and strides, paddings parameters.
 )DOC");
     AddAttr<std::vector<int>>("strides", "strides of convolution operator.");
     AddAttr<std::vector<int>>("paddings", "paddings of convolution operator.");
+    AddAttr<int>(
+        "groups",
+        "group size of convolution operator. "
+        "Refer to grouped convolution in Alex Krizhevsky's paper: "
+        "when group=2, the first half of the filters are only connected to the "
+        "first half of the input channels, and the second half only connected "
+        "to the second half.")
+        .SetDefault(1);
   }
 };
 
diff --git a/paddle/operators/gemm_conv_op.h b/paddle/operators/gemm_conv_op.h
index 3b7ba685c8..8ac92d3bd2 100644
--- a/paddle/operators/gemm_conv_op.h
+++ b/paddle/operators/gemm_conv_op.h
@@ -38,6 +38,7 @@ class GemmConvKernel : public framework::OpKernel {
 
     std::vector<int> strides = context.Attr<std::vector<int>>("strides");
     std::vector<int> paddings = context.Attr<std::vector<int>>("paddings");
+    int groups = context.Attr<int>("groups");
 
     int batch_size = input->dims()[0];
     int input_channels = input->dims()[1];
@@ -51,11 +52,11 @@ class GemmConvKernel : public framework::OpKernel {
         paddle::operators::math::ColFormat::kCFO, Place, T>
         im2col;
     // use col_shape in the im2col calculation
-    framework::DDim col_shape = {input_channels, filter_height, filter_width,
-                                 output_height, output_width};
+    framework::DDim col_shape = {input_channels / groups, filter_height,
+                                 filter_width, output_height, output_width};
     // use col_matrix_shape in the gemm calculation
     framework::DDim col_matrix_shape = {
-        input_channels * filter_height * filter_width,
+        input_channels / groups * filter_height * filter_width,
         output_height * output_width};
     Tensor col;
     col.mutable_data<T>(col_shape, context.GetPlace());
@@ -78,16 +79,26 @@ class GemmConvKernel : public framework::OpKernel {
         const_cast<platform::DeviceContext*>(context.device_context_);
 
     // convolution operator: im2col + gemm
+    int in_step = input_channels / groups;
+    int out_step = output_channels / groups;
     for (int i = 0; i < batch_size; i++) {
-      // im2col
-      Tensor in_slice = input->Slice<T>(i, i + 1).Resize(input_shape);
-      im2col(in_slice, col, strides[0], strides[1], paddings[0], paddings[1],
-             device_context);
-
-      // gemm
-      Tensor out_slice = output->Slice<T>(i, i + 1).Resize(output_matrix_shape);
-      math::matmul<Place, T>(filter, false, col_matrix, false, T(1.0),
-                             &out_slice, T(0.0), device_context);
+      Tensor in_slice_batch = input->Slice<T>(i, i + 1).Resize(input_shape);
+      Tensor out_slice_batch =
+          output->Slice<T>(i, i + 1).Resize(output_matrix_shape);
+      for (int g = 0; g < groups; g++) {
+        // im2col
+        Tensor in_slice =
+            in_slice_batch.Slice<T>(g * in_step, (g + 1) * in_step);
+        im2col(in_slice, col, strides[0], strides[1], paddings[0], paddings[1],
+               device_context);
+
+        // gemm
+        Tensor out_slice =
+            out_slice_batch.Slice<T>(g * out_step, (g + 1) * out_step);
+        Tensor filter_slice = filter.Slice<T>(g * out_step, (g + 1) * out_step);
+        math::matmul<Place, T>(filter_slice, false, col_matrix, false, T(1.0),
+                               &out_slice, T(0.0), device_context);
+      }
     }
   }
 };
@@ -114,6 +125,7 @@ class GemmConvGradKernel : public framework::OpKernel {
 
     std::vector<int> strides = context.Attr<std::vector<int>>("strides");
     std::vector<int> paddings = context.Attr<std::vector<int>>("paddings");
+    // int groups = context.Attr<int>("groups");
 
     int batch_size = input->dims()[0];
     int input_channels = input->dims()[1];
-- 
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