/* 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. */

#pragma once
#include <math.h>
#include <type_traits>
#include "paddle/fluid/framework/op_registry.h"
#include "paddle/fluid/operators/elementwise/elementwise_op_function.h"
#include "paddle/fluid/platform/transform.h"

namespace paddle {
namespace operators {

#define COMPARE_FUNCTOR(func_name, op)                           \
  template <typename InT, typename OutT = bool>                  \
  struct func_name {                                             \
    using ELEM_TYPE = InT;                                       \
    HOSTDEVICE OutT operator()(const InT a, const InT b) const { \
      return static_cast<OutT>(a op b);                          \
    }                                                            \
  };

COMPARE_FUNCTOR(LessThanFunctor, <)
COMPARE_FUNCTOR(LessEqualFunctor, <=)
COMPARE_FUNCTOR(GreaterThanFunctor, >)
COMPARE_FUNCTOR(GreaterEqualFunctor, >=)
#undef COMPARE_FUNCTOR

template <typename InT, typename OutT = bool>
struct EqualFunctor {
  using ELEM_TYPE = InT;
  HOSTDEVICE OutT operator()(const InT a, const InT b) const {
    if (std::is_floating_point<InT>::value) {
      // This branch will be optimized while compiling if T is integer. It is
      // safe to cast a and b to double.
      return static_cast<OutT>(fabs(static_cast<double>(a - b)) < 1e-8);
    } else {
      return static_cast<OutT>(a == b);
    }
  }
};

template <typename InT, typename OutT = bool>
struct NotEqualFunctor {
  using ELEM_TYPE = InT;
  HOSTDEVICE bool operator()(const InT a, const InT b) const {
    return !EqualFunctor<InT, OutT>()(a, b);
  }
};

template <typename DeviceContext, typename Functor, typename InverseFunctor>
class CompareOpKernel
    : public framework::OpKernel<typename Functor::ELEM_TYPE> {
 public:
  void Compute(const framework::ExecutionContext& context) const override {
    using T = typename Functor::ELEM_TYPE;
    using Tensor = framework::Tensor;

    auto* x = context.Input<Tensor>("X");
    auto* y = context.Input<Tensor>("Y");
    auto* z = context.Output<Tensor>("Out");
    int axis = context.Attr<int>("axis");

    auto x_dims = x->dims();
    auto y_dims = y->dims();
    if (x_dims.size() >= y_dims.size()) {
      ElementwiseComputeEx<Functor, DeviceContext, T, bool>(context, x, y, axis,
                                                            Functor(), z);
    } else {
      ElementwiseComputeEx<InverseFunctor, DeviceContext, T, bool>(
          context, x, y, axis, InverseFunctor(), z);
    }
  }
};

}  // namespace operators
}  // namespace paddle

#define REGISTER_COMPARE_KERNEL(op_type, dev, functor, inverse_functor)       \
  REGISTER_OP_##dev##_KERNEL(op_type,                                         \
                             ::paddle::operators::CompareOpKernel<            \
                                 ::paddle::platform::dev##DeviceContext,      \
                                 functor<bool>, inverse_functor<bool>>,       \
                             ::paddle::operators::CompareOpKernel<            \
                                 ::paddle::platform::dev##DeviceContext,      \
                                 functor<int>, inverse_functor<int>>,         \
                             ::paddle::operators::CompareOpKernel<            \
                                 ::paddle::platform::dev##DeviceContext,      \
                                 functor<int16_t>, inverse_functor<int16_t>>, \
                             ::paddle::operators::CompareOpKernel<            \
                                 ::paddle::platform::dev##DeviceContext,      \
                                 functor<int64_t>, inverse_functor<int64_t>>, \
                             ::paddle::operators::CompareOpKernel<            \
                                 ::paddle::platform::dev##DeviceContext,      \
                                 functor<float>, inverse_functor<float>>,     \
                             ::paddle::operators::CompareOpKernel<            \
                                 ::paddle::platform::dev##DeviceContext,      \
                                 functor<double>, inverse_functor<double>>);