Add flatten op (#12341)

* add flatten op

paddle/fluid/operators/CMakeLists.txt

@@ -271,6 +271,8 @@ op_library(parallel_do_op DEPS executor)
 op_library(unsqueeze_op DEPS reshape_op)
 op_library(squeeze_op DEPS reshape_op)
 op_library(extract_rows_op DEPS memory)
+op_library(flatten_op DEPS reshape_op)
+
 
 if (WITH_GPU)
     op_library(conv_op DEPS vol2col depthwise_conv im2col)

paddle/fluid/operators/flatten_op.cc

+/* Copyright (c) 2018 PaddlePaddle Authors. All Rights Reserved.
+
+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 <vector>
+#include "paddle/fluid/framework/op_registry.h"
+
+namespace paddle {
+namespace operators {
+
+using Tensor = framework::Tensor;
+
+class FlattenOpInferShape : public framework::InferShapeBase {
+ public:
+  void operator()(framework::InferShapeContext *ctx) const override {
+    PADDLE_ENFORCE(ctx->HasInput("X"),
+                   "Input (X) of Flatten op should not be null.");
+    PADDLE_ENFORCE(ctx->HasOutput("Out"),
+                   "Output (Output) of Flatten op should not be null.");
+    const auto &axis = ctx->Attrs().Get<int>("axis");
+    const auto &in_dims = ctx->GetInputDim("X");
+    PADDLE_ENFORCE(axis >= 0, "The axis should be greater than or equal to 0.");
+    PADDLE_ENFORCE(
+        axis <= in_dims.size(),
+        "The axis should be less than or equal to input tensor's rank.");
+
+    const auto &out_dims = GetOutputShape(axis, in_dims);
+    ctx->SetOutputDim("Out", framework::make_ddim(out_dims));
+    if (in_dims[0] == out_dims[0]) {
+      // Only pass LoD when the first dimension of output and Input(X)
+      // are the same.
+      ctx->ShareLoD("X", "Out");
+    }
+  }
+
+  static std::vector<int32_t> GetOutputShape(const int axis,
+                                             const framework::DDim &in_dims) {
+    int64_t outer = 1, inner = 1;
+    for (int i = 0; i < in_dims.size(); ++i) {
+      if (i < axis) {
+        outer *= in_dims[i];
+      } else {
+        inner *= in_dims[i];
+      }
+    }
+    std::vector<int32_t> out_shape(2);
+    out_shape[0] = outer;
+    out_shape[1] = inner;
+    return out_shape;
+  }
+};
+
+class FlattenOp : public framework::OperatorBase {
+ public:
+  using OperatorBase::OperatorBase;
+
+ private:
+  void RunImpl(const framework::Scope &scope,
+               const platform::Place &place) const override {
+    auto &axis = Attr<int>("axis");
+    auto in_dims =
+        scope.FindVar(Input("X"))->Get<framework::LoDTensor>().dims();
+    const auto &out_dims = FlattenOpInferShape::GetOutputShape(axis, in_dims);
+
+    framework::AttributeMap attrs;
+    attrs["shape"] = out_dims;
+    attrs["inplace"] = false;
+    // Invoke Reshape Op
+    auto reshape_op = framework::OpRegistry::CreateOp(
+        "reshape", {{"X", {Input("X")}}, {"Shape", {}}},
+        {{"Out", {Output("Out")}}}, attrs);
+    reshape_op->Run(scope, place);
+  }
+};
+
+class FlattenOpMaker : public framework::OpProtoAndCheckerMaker {
+ public:
+  void Make() override {
+    AddInput("X", "(Tensor) A tensor of rank >= axis.");
+    AddOutput("Out",
+              "A 2D tensor is reshaped input tensor. The input dimensions"
+              "up to axis are flattened to the outer dimension of the output"
+              "and the remaining input dimensions are flattened into the inner"
+              "dimension of the output.");
+    AddAttr<int>("axis",
+                 "(int)"
+                 "Indicate up to which input dimensions (exclusive) should be"
+                 "flattened to the outer dimension of the output. The value"
+                 "for axis must be in the range [0, R], where R is the rank of"
+                 "the input tensor. When axis = 0, the shape of the output"
+                 "tensor is (1, (d_0 X d_1 ... d_n), where the shape of the"
+                 "input tensor is (d_0, d_1, ... d_n).")
+        .SetDefault(1);
+    AddComment(R"DOC(
+Flatten Operator
+
+Flattens the input tensor into a 2D matrix.
+
+Examples:
+Case 1:
+  Given
+    X.shape = (3, 100, 100, 4)
+  and
+    axis = 2
+  We get:
+    Out.shape = (3 * 100, 4 * 100)
+
+Case 2:
+  Given
+    X.shape = (3, 100, 100, 4)
+  and
+    axis = 0
+  We get:
+    Out.shape = (1, 3 * 100 * 100 * 4)
+)DOC");
+  }
+};
+
+class FlattenGradInferShape : public framework::InferShapeBase {
+ public:
+  void operator()(framework::InferShapeContext *context) const override {
+    context->SetOutputDim(framework::GradVarName("X"),
+                          context->GetInputDim("X"));
+    context->ShareLoD("X", framework::GradVarName("X"));
+  }
+};
+
+class FlattenGradOp : public framework::OperatorBase {
+ public:
+  using OperatorBase::OperatorBase;
+
+ private:
+  void RunImpl(const framework::Scope &scope,
+               const platform::Place &place) const override {
+    auto dx_name = Output(framework::GradVarName("X"));
+    auto dout_name = Input(framework::GradVarName("Out"));
+    auto in_dims =
+        scope.FindVar(Input("X"))->Get<framework::LoDTensor>().dims();
+    framework::AttributeMap attrs;
+    attrs["shape"] = framework::vectorize2int(in_dims);
+    attrs["inplace"] = false;
+
+    auto reshape_op = framework::OpRegistry::CreateOp(
+        "reshape", {{"X", {dout_name}}, {"Shape", {}}}, {{"Out", {dx_name}}},
+        attrs);
+    reshape_op->Run(scope, place);
+  }
+};
+
+}  // namespace operators
+}  // namespace paddle
+
+USE_OP(reshape);
+
+namespace ops = paddle::operators;
+REGISTER_OPERATOR(flatten, ops::FlattenOp, ops::FlattenOpMaker,
+                  ops::FlattenOpInferShape,
+                  paddle::framework::DefaultGradOpDescMaker<true>);
+REGISTER_OPERATOR(flatten_grad, ops::FlattenGradOp, ops::FlattenGradInferShape);

python/paddle/fluid/tests/unittests/test_flatten_op.py

+#   Copyright (c) 2018 PaddlePaddle Authors. All Rights Reserved.
+#
+# 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.
+
+import unittest
+import numpy as np
+
+from op_test import OpTest
+
+
+class TestFlattenOp(OpTest):
+    def setUp(self):
+        self.op_type = "flatten"
+        self.init_test_case()
+        self.inputs = {"X": np.random.random(self.in_shape).astype("float32")}
+        self.init_attrs()
+        self.outputs = {"Out": self.inputs["X"].reshape(self.new_shape)}
+
+    def test_check_output(self):
+        self.check_output()
+
+    def test_check_grad(self):
+        self.check_grad(["X"], "Out")
+
+    def init_test_case(self):
+        self.in_shape = (3, 2, 2, 5)
+        self.axis = 1
+        self.new_shape = (3, 20)
+
+    def init_attrs(self):
+        self.attrs = {"axis": self.axis}
+
+
+class TestFlattenOp(TestFlattenOp):
+    def init_test_case(self):
+        self.in_shape = (3, 2, 2, 3)
+        self.axis = 0
+        self.new_shape = (1, 36)
+
+
+class TestFlattenOpWithDefaultAxis(TestFlattenOp):
+    def init_test_case(self):
+        self.in_shape = (3, 2, 2, 3)
+        self.new_shape = (3, 12)
+
+    def init_attrs(self):
+        self.attrs = {}
+
+
+class TestFlattenOpSixDims(TestFlattenOp):
+    def init_test_case(self):
+        self.in_shape = (3, 2, 3, 2, 4, 4)
+        self.axis = 4
+        self.new_shape = (36, 16)
+
+
+if __name__ == "__main__":
+    unittest.main()