/*******************************************************************************
 *
 * MIT License
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 * Copyright (c) 2020 Advanced Micro Devices, Inc.
 *
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 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
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 *
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 *******************************************************************************/
#ifndef CK_REDUCTION_OPERATOR_HPP
#define CK_REDUCTION_OPERATOR_HPP

#include "config.hpp"
#include "data_type.hpp"
#include "type.hpp"

namespace ck {

namespace reduce {

// Every binary operator used in reduction is represented by a templated functor class. Each functor
// class must provide at least
// three members:
// 1) GetIdentityValue() -- the interface to return the "identity element" for the binary
// operator, "identity element" is the unique
//                    element in the algebraic space that doesn't affect the value of other elements
//                    when operated against them, and the concept is similar to zero vector in
//                    vector space
//                    (http://pages.cs.wisc.edu/~matthewb/pages/notes/pdf/linearalgebra/VectorSpaces.pdf).
// 2) IsCompatibleInMemoryDataOperation() -- return true if the reduction task corresponding to this
// operator can use the InMemoryDataOperation to finalize, or else it return false 3) operator() --
// the first argument of the operator must be both an input & output, and the corresponding variable
// usually stores
//                  the accumulated result of many operator() calls; the second argument is only an
//                  input. For indexable binary
//                  operator, the second version of operator() has third argument (which is an
//                  output) to indicate whether the
//                  accumulated value (the first argument) has changed, in which case the recorded
//                  accumulated index also need be
//                  changed.

struct Add
{
    template <typename T>
    __host__ __device__ static constexpr T GetIdentityValue()
    {
        return type_convert<T>(0.0f);
    };

    __host__ __device__ static constexpr bool
    IsCompatibleInMemoryDataOperation(InMemoryDataOperationEnum operation)
    {
        return operation == InMemoryDataOperationEnum::AtomicAdd ||
               operation == InMemoryDataOperationEnum::Set;
    };

    template <typename T>
    __host__ __device__ inline constexpr void operator()(T& a, T b) const
    {
        static_assert(is_same<T, float>::value || is_same<T, double>::value ||
                          is_same<T, int32_t>::value,
                      "The data type is not supported by the Add accumulator!");

        a = a + b;
    }
};

struct Mul
{
    template <typename T>
    __host__ __device__ static constexpr T GetIdentityValue()
    {
        return type_convert<T>(1.0f);
    };

    __host__ __device__ static constexpr bool
    IsCompatibleInMemoryDataOperation(InMemoryDataOperationEnum operation)
    {
        return operation == InMemoryDataOperationEnum::Set;
    };

    template <typename T>
    __host__ __device__ inline constexpr void operator()(T& a, T b) const
    {
        static_assert(is_same<T, float>::value || is_same<T, double>::value ||
                          is_same<T, int32_t>::value,
                      "The data type is not supported by the Mul accumulator!");

        a = a * b;
    }
};

struct Max
{
    template <typename T>
    __host__ __device__ static constexpr T GetIdentityValue()
    {
        return NumericLimits<T>::Lowest();
    };

    __host__ __device__ static constexpr bool
    IsCompatibleInMemoryDataOperation(InMemoryDataOperationEnum operation)
    {
        // ToChange: atomic_max to be added
        return operation == InMemoryDataOperationEnum::Set;
    };

    template <typename T>
    __host__ __device__ inline constexpr void operator()(T& a, T b) const
    {
        static_assert(is_same<T, float>::value || is_same<T, double>::value ||
                          is_same<T, half_t>::value || is_same<T, int32_t>::value ||
                          is_same<T, int8_t>::value,
                      "The data type is not supported by the Max accumulator!");

        if(a < b)
            a = b;
    }

    template <typename T>
    __host__ __device__ inline constexpr void operator()(T& a, T b, bool& changed) const
    {
        static_assert(is_same<T, float>::value || is_same<T, double>::value ||
                          is_same<T, half_t>::value || is_same<T, int32_t>::value ||
                          is_same<T, int8_t>::value,
                      "The data type is not supported by the Max accumulator!");

        if(a < b)
        {
            a       = b;
            changed = true;
        }
    }
};

struct Min
{
    template <typename T>
    __host__ __device__ static constexpr T GetIdentityValue()
    {
        return NumericLimits<T>::Max();
    };

    __host__ __device__ static constexpr bool
    IsCompatibleInMemoryDataOperation(InMemoryDataOperationEnum operation)
    {
        // ToChange: atomic_min to be added
        return operation == InMemoryDataOperationEnum::Set;
    };

    template <typename T>
    __host__ __device__ inline constexpr void operator()(T& a, T b) const
    {
        static_assert(is_same<T, float>::value || is_same<T, double>::value ||
                          is_same<T, half_t>::value || is_same<T, int32_t>::value ||
                          is_same<T, int8_t>::value,
                      "The data type is not supported by the Min accumulator!");

        if(a > b)
            a = b;
    }

    template <typename T>
    __host__ __device__ inline constexpr void operator()(T& a, T b, bool& changed) const
    {
        static_assert(is_same<T, float>::value || is_same<T, double>::value ||
                          is_same<T, half_t>::value || is_same<T, int32_t>::value ||
                          is_same<T, int8_t>::value,
                      "The data type is not supported by the Min accumulator!");

        if(a > b)
        {
            a       = b;
            changed = true;
        }
    }
};

struct AMax
{
    template <typename T>
    __host__ __device__ static constexpr T GetIdentityValue()
    {
        return type_convert<T>(0.0f);
    };

    __host__ __device__ static constexpr bool
    IsCompatibleInMemoryDataOperation(InMemoryDataOperationEnum operation)
    {
        // ToChange: atomic_max to be added
        return operation == InMemoryDataOperationEnum::Set;
    };

    template <typename T>
    __host__ __device__ inline constexpr void operator()(T& a, T b) const
    {
        static_assert(is_same<T, float>::value || is_same<T, double>::value ||
                          is_same<T, half_t>::value || is_same<T, int32_t>::value ||
                          is_same<T, int8_t>::value,
                      "The data type is not supported by the AMax accumulator!");

        if(a < b)
            a = b;
    }

    template <typename T>
    __host__ __device__ inline constexpr void operator()(T& a, T b, bool& changed) const
    {
        static_assert(is_same<T, float>::value || is_same<T, double>::value ||
                          is_same<T, half_t>::value || is_same<T, int32_t>::value ||
                          is_same<T, int8_t>::value,
                      "The data type is not supported by the AMax accumulator!");

        if(a < b)
        {
            a       = b;
            changed = true;
        }
    }
};

template <typename T>
constexpr T GetIdentityValueForInMemoryDataOperation(InMemoryDataOperationEnum operation)
{
    T result = ck::type_convert<T>(0.0f);

    if(operation == InMemoryDataOperationEnum::AtomicMax)
        result = ck::NumericLimits<T>::Lowest();

    return (result);
};

template <InMemoryDataOperationEnum Operation, typename DataType>
struct InMemoryDataOperatonSupportedOnDataType
{
    static constexpr bool value = false;
};

template <typename DataType>
struct InMemoryDataOperatonSupportedOnDataType<InMemoryDataOperationEnum::AtomicAdd, DataType>
{
    static constexpr bool value =
        is_same<DataType, float>::value || is_same<DataType, double>::value;
};

template <typename DataType>
struct InMemoryDataOperatonSupportedOnDataType<InMemoryDataOperationEnum::AtomicMax, DataType>
{
    static constexpr bool value =
        is_same<DataType, float>::value || is_same<DataType, double>::value;
};

template <typename DataType>
struct InMemoryDataOperatonSupportedOnDataType<InMemoryDataOperationEnum::Set, DataType>
{
    static constexpr bool value =
        is_same<DataType, float>::value || is_same<DataType, double>::value ||
        is_same<DataType, half_t>::value || is_same<DataType, bhalf_t>::value ||
        is_same<DataType, int8_t>::value || is_same<DataType, int32_t>::value;
};

template <typename DataType>
struct InMemoryDataOperatonSupportedOnDataType<InMemoryDataOperationEnum::Add, DataType>
{
    static constexpr bool value =
        is_same<DataType, float>::value || is_same<DataType, double>::value ||
        is_same<DataType, half_t>::value || is_same<DataType, int8_t>::value ||
        is_same<DataType, int32_t>::value;
};

}; // end of namespace reduce

} // end of namespace ck

#endif