/* Copyright (c) 2016 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 "paddle/fluid/operators/dropout_op.h"

namespace paddle {
namespace operators {

using framework::Tensor;

class DropoutOp : public framework::OperatorWithKernel {
 public:
  using framework::OperatorWithKernel::OperatorWithKernel;

  void InferShape(framework::InferShapeContext* ctx) const override {
    PADDLE_ENFORCE(ctx->HasInput("X"), "Input(X) must not be null.");

    auto x_dims = ctx->GetInputDim("X");
    ctx->SetOutputDim("Out", x_dims);
    if (ctx->Attrs().Get<bool>("is_test") == false) {
      ctx->SetOutputDim("Mask", x_dims);
    }
    ctx->ShareLoD("X", /*->*/ "Out");
  }
};

class DropoutOpMaker : public framework::OpProtoAndCheckerMaker {
 public:
  DropoutOpMaker(OpProto* proto, OpAttrChecker* op_checker)
      : OpProtoAndCheckerMaker(proto, op_checker) {
    AddInput("X", "The input of dropout op.");
    AddOutput("Out", "The output of dropout op.");
    AddOutput("Mask", "The random sampled dropout mask.").AsIntermediate();

    AddAttr<float>("dropout_prob", "Probability of setting units to zero.")
        .SetDefault(.5f)
        .AddCustomChecker([](const float& drop_p) {
          PADDLE_ENFORCE(drop_p >= 0.0f && drop_p <= 1.0f,
                         "'dropout_prob' must be between 0.0 and 1.0.");
        });
    AddAttr<bool>("is_test", "True if in test phase.").SetDefault(false);
    AddAttr<bool>("fix_seed",
                  "A flag indicating whether to use a fixed seed to generate "
                  "random mask. NOTE: DO NOT set this flag to true in "
                  "training. Setting this flag to true is only useful in "
                  "unittest or for debug that always the same output units "
                  "will be dropped.")
        .SetDefault(false);
    AddAttr<int>("seed", "Dropout random seed.").SetDefault(0);

    AddComment(R"DOC(
Dropout Operator.

Dropout refers to randomly dropping out units in a nerual network. It is a
regularization technique for reducing overfitting by preventing neuron
co-adaption during training. The dropout operator randomly set (according to
the given dropout probability) the outputs of some units to zero, while others
are set equal to their corresponding inputs.

)DOC");
  }
};

class DropoutOpGrad : public framework::OperatorWithKernel {
 public:
  using framework::OperatorWithKernel::OperatorWithKernel;

  void InferShape(framework::InferShapeContext* ctx) const override {
    PADDLE_ENFORCE_EQ(ctx->Attrs().Get<bool>("is_test"), false,
                      "GradOp is only callable when is_test is false");

    PADDLE_ENFORCE(ctx->HasInput("X"), "Input(X) must not be null.");
    PADDLE_ENFORCE(ctx->HasInput("Mask"), "Mask must not be null.");
    PADDLE_ENFORCE(ctx->HasInput(framework::GradVarName("Out")),
                   "Input(Out@GRAD) must not be null.");

    auto x_dims = ctx->GetInputDim("X");
    auto out_dims = ctx->GetInputDim(framework::GradVarName("Out"));
    PADDLE_ENFORCE_EQ(x_dims, out_dims,
                      "Dimensions of Input(X) and Out@Grad must be the same.");
    auto mask_dims = ctx->GetInputDim("Mask");
    PADDLE_ENFORCE_EQ(x_dims, mask_dims,
                      "Dimensions of Input(X) and Mask must be the same.");

    ctx->SetOutputDim(framework::GradVarName("X"), x_dims);
  }
};

}  // namespace operators
}  // namespace paddle

namespace ops = paddle::operators;
REGISTER_OPERATOR(dropout, ops::DropoutOp, ops::DropoutOpMaker,
                  paddle::framework::DefaultGradOpDescMaker<true>)
REGISTER_OPERATOR(dropout_grad, ops::DropoutOpGrad)
REGISTER_OP_CPU_KERNEL(
    dropout, ops::CPUDropoutKernel<paddle::platform::CPUDeviceContext, float>);
REGISTER_OP_CPU_KERNEL(
    dropout_grad,
    ops::DropoutGradKernel<paddle::platform::CPUDeviceContext, float>);