/*
 * Copyright (c) 2020, NVIDIA CORPORATION. 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.
 */

#ifndef COMMON_CUH
#define COMMON_CUH

#include "cublas_v2.h"
#ifndef CUDART_VERSION
#error CUDART_VERSION Undefined!
#elif (CUDART_VERSION >= 11050)
#include <cub/cub.cuh>
#else
#include "3rdparty/cub/cub.cuh"
#endif 

#define HDI inline __host__ __device__

using kv_float = cub::KeyValuePair<float, float>;
using kv_half = cub::KeyValuePair<half, half>;
using kv_half2 = cub::KeyValuePair<half2, half2>;

template <typename T>
__device__ inline T tanh(const T& x);

template <typename T>
__device__ inline T rsqrt(const T& x);

template <typename T>
__device__ inline T exp(const T& x);


// Float32 Operations
template <>
__device__ inline float tanh(const float& x)
{
    return tanhf(x);
}

template <>
__device__ inline float rsqrt(const float& x)
{
    return rsqrtf(x);
}

template <>
__device__ inline float exp(const float& x)
{
    return expf(x);
}


__device__ inline kv_float operator+(const kv_float& a, const kv_float& b)
{
    return kv_float(a.key + b.key, a.value + b.value);
}


// Half Operations

__device__ inline half2 __hadd2_with_fallback(const half2 a, const half2 b)
{
#if __CUDA_ARCH__ >= 530
    return __hadd2(a, b);
#else
    float2 out{};
    out.x = __half2float(a.x) + __half2float(b.x);
    out.y = __half2float(a.y) + __half2float(b.y);
    return __float22half2_rn(out);
#endif
}

#if __CUDA_ARCH__ < 530

template <typename T>
__device__ inline T operator+(const T& a, const T& b);

template <typename T>
__device__ inline T operator*(const T& a, const T& b);


template <>
__device__ inline half2 operator+(const half2& a, const half2& b)
{
    return __hadd2_with_fallback(a, b);
}

template <>
__device__ inline half2 operator*(const half2& a, const half2& b)
{
    float2 out{};
    out.x = __half2float(a.x) * __half2float(b.x);
    out.y = __half2float(a.y) * __half2float(b.y);
    return __float22half2_rn(out);
}

template <typename T>
__device__ inline T operator+(const T& a, const T& b);


template <typename T>
__device__ inline T operator/(const T& a, const T& b);


template <typename T>
__device__ inline T& operator+=(T& a, const T& b);

template <typename T>
__device__ inline T operator-(const T& a, const T& b);

template <typename T>
__device__ inline T operator*(const T& a, const T& b);


template <>
__device__ inline half operator+(const half& a, const half& b)
{
    return __float2half(__half2float(a) + __half2float(b));
}

template <>
__device__ inline half& operator+=(half& a, const half& b)
{
    a = __float2half(__half2float(a) + __half2float(b));
    return a;
}

template <>
__device__ inline half operator-(const half& a, const half& b)
{
    return __float2half(__half2float(a) - __half2float(b));
}

template <>
__device__ inline half operator*(const half& a, const half& b)
{
    return __float2half(__half2float(a) * __half2float(b));
}

template <>
__device__ inline half operator/(const half& a, const half& b)
{
    return __float2half(__half2float(a) / __half2float(b));
}

#endif

template <>
__device__ inline half tanh(const half& x)
{
    const float tmp = tanhf(__half2float(x));
    return __float2half(tmp);
}

template <>
__device__ inline half2 tanh(const half2& x)
{
    // at the moment, there is no half2 tanh builtin
    float2 tmp = (__half22float2(x));
    tmp.x = tanhf(tmp.x);
    tmp.y = tanhf(tmp.y);
    return __float22half2_rn(tmp);
}

template <>
__device__ inline half rsqrt(const half& x)
{
#if __CUDA_ARCH__ >= 530
    return hrsqrt(x);
#else
    return __float2half(rsqrt(__half2float(x)));
#endif
}

template <>
__device__ inline half exp(const half& x)
{
#if __CUDA_ARCH__ >= 530
    return hexp(x);
#else
    return __float2half(exp(__half2float(x)));
#endif
}

__device__ inline kv_half operator+(const kv_half& a, const kv_half& b)
{
    const half2 a2 = __halves2half2(a.key, a.value);
    const half2 b2 = __halves2half2(b.key, b.value);
    const half2 res = __hadd2_with_fallback(a2, b2);
    return kv_half(res.x, res.y);
}

__device__ inline kv_half2 operator+(const kv_half2& a, const kv_half2& b)
{
    return kv_half2(__hadd2_with_fallback(a.key, b.key), __hadd2_with_fallback(a.value, b.value));
}


// Helper Functions

template <typename T>
using kvp = cub::KeyValuePair<T, T>;

template <typename T, typename R, typename P, int TPB>
__device__ inline void layerNorm(
    const kvp<R>& threadData, const int ld, const int offset, const P* beta, const P* gamma, T* output)
{
    // Assuming threadData is already divided by ld

    using BlockReduce = cub::BlockReduce<kvp<R>, TPB>;
    __shared__ typename BlockReduce::TempStorage temp_storage;
    __shared__ R mu;     // mean
    __shared__ R rsigma; // 1 / std.dev.

    const auto sumKV = BlockReduce(temp_storage).Reduce(threadData, cub::Sum());

    if (threadIdx.x == 0)
    {
        mu = sumKV.key;
        rsigma = rsqrt(sumKV.value - mu * mu);
    }
    __syncthreads();

    for (int i = threadIdx.x; i < ld; i += TPB)
    {
        const int idx = offset + i;
        const R val = output[idx];
        const R g(gamma[i]);
        const R b(beta[i]);
        output[idx] = g * (val - mu) * rsigma + b;
    }
}

template <typename T, typename P, int TPB>
__device__ inline void layerNormSmall(
    const T val, const kvp<T>& threadData, const int ld, const int idx, const P* beta, const P* gamma, T* output)
{
    // Assuming threadData is already divided by ld
    // Small settings: the block covers the leading dimension TPB >= ld. The input
    // value is available in a register

    using BlockReduce = cub::BlockReduce<kvp<T>, TPB>;
    __shared__ typename BlockReduce::TempStorage temp_storage;
    __shared__ T mu;     // mean
    __shared__ T rsigma; // 1 / std.dev.

    const auto sumKV = BlockReduce(temp_storage).Reduce(threadData, cub::Sum());

    if (threadIdx.x == 0)
    {
        mu = sumKV.key;
        rsigma = rsqrt(sumKV.value - mu * mu);
    }
    __syncthreads();

    if (threadIdx.x < ld)
    {
        const T g(gamma[threadIdx.x]);
        const T b(beta[threadIdx.x]);
        output[idx] = g * (val - mu) * rsigma + b;
    }
}

template <typename T, unsigned TPB>
__device__ inline void scaledSoftmaxSmall(
    const int ld, const int lastValid, const float rsqrtHeadSize, const T* input, T* output)
{

    using BlockReduce = cub::BlockReduce<float, TPB>;

    __shared__ typename BlockReduce::TempStorage tmpStorage;

    __shared__ float rZ;
    __shared__ float fMax;

    const int offset = (blockIdx.y * gridDim.x + blockIdx.x) * ld;

    const float w(rsqrtHeadSize);
    cub::Sum sum;
    float threadData(-FLT_MAX);

    const int idx = offset + threadIdx.x;
    if (threadIdx.x < lastValid)
    {
        threadData = input[idx];
    }

    const float maxElem = BlockReduce(tmpStorage).Reduce(threadData, cub::Max());
    if (threadIdx.x == 0)
    {
        fMax = maxElem;
    }
    __syncthreads();

    if (threadIdx.x < lastValid)
    {
        threadData = exp((threadData - fMax) * w);
    }
    else
    {
        threadData = 0;
    }

    const auto Z = BlockReduce(tmpStorage).Reduce(threadData, sum);

    if (threadIdx.x == 0)
    {
        rZ = (1.f) / Z;
    }
    __syncthreads();

    if (threadIdx.x < ld)
    {
        // this will be 0 for threadIdx.x >= lastValid
        output[idx] = T(threadData * rZ);
    }
}

template <typename T, unsigned TPB>
__device__ inline void scaledSoftmax(
    const int ld, const int lastValid, const float rsqrtHeadSize, const T* input, T* output)
{

    using BlockReduce = cub::BlockReduce<float, TPB>;
    __shared__ typename BlockReduce::TempStorage tmpStorage;

    __shared__ float rZ;
    __shared__ float fMax;

    const int offset = (blockIdx.y * gridDim.x + blockIdx.x) * ld;

    const float w(rsqrtHeadSize);
    cub::Sum sum;
    float threadData(-FLT_MAX);

    if (lastValid >= blockDim.x)
    {
        threadData = 0;
    }
    for (int i = threadIdx.x; i < lastValid; i += TPB)
    {
        const int idx = offset + i;
        threadData = input[idx];
    }

    const float maxElem = BlockReduce(tmpStorage).Reduce(threadData, cub::Max());
    if (threadIdx.x == 0)
    {
        fMax = maxElem;
    }
    __syncthreads();

    if (lastValid < blockDim.x)
    {
        if (threadIdx.x >= lastValid)
        {
            threadData = 0;
        }
    }
    for (int i = threadIdx.x; i < lastValid; i += TPB)
    {
        threadData += exp((threadData - fMax) * w);
    }

    const auto Z = BlockReduce(tmpStorage).Reduce(threadData, sum);

    if (threadIdx.x == 0)
    {
        rZ = 1.f / Z;
    }
    __syncthreads();

    for (int i = threadIdx.x; i < ld; i += TPB)
    {
        const int idx = offset + i;
        const float val = (i < lastValid) ? exp(float(input[idx]) * w) * rZ : 0.f;
        output[idx] = T(val);
    }
}

template <typename IntType>
constexpr HDI IntType ceildiv(IntType a, IntType b)
{
    return (a + b - 1) / b;
}
template <typename IntType>
constexpr HDI IntType alignTo(IntType a, IntType b)
{
    return ceildiv(a, b) * b;
}

template <int VPT>
struct BytesToType;

template <>
struct BytesToType<2>
{
    using type = uint16_t;
};
template <>
struct BytesToType<4>
{
    using type = uint32_t;
};
template <>
struct BytesToType<8>
{
    using type = uint64_t;
};
template <>
struct BytesToType<16>
{
    using type = float4;
};

template <int Bytes>
__device__ inline void copy(const void* local, void* data)
{
    using T = typename BytesToType<Bytes>::type;

    const T* in = static_cast<const T*>(local);
    T* out = static_cast<T*>(data);
    *out = *in;
}

template <typename T>
__device__ inline T myExp(const T x);

template <>
__device__ inline half myExp<half>(const half x)
{
    return exp(x);
}
template <>
__device__ inline float myExp<float>(const float x)
{
    return __expf(x);
}

#endif // #ifndef COMMON_CUH
