/*
 * The MIT License (MIT)
 *
 * Copyright (c) 2015-2022 Advanced Micro Devices, Inc. All rights reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
#ifndef MIGRAPHX_GUARD_AMDMIGRAPHX_CPU_PARALLEL_HPP
#define MIGRAPHX_GUARD_AMDMIGRAPHX_CPU_PARALLEL_HPP

// #define MIGRAPHX_DISABLE_OMP
#include <cmath>
#include <migraphx/config.hpp>
#ifdef MIGRAPHX_DISABLE_OMP
#include <migraphx/par_for.hpp>
#else

#ifdef __clang__
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wreserved-identifier"
#endif
#include <omp.h>
#ifdef __clang__
#pragma clang diagnostic pop
#endif

#endif

namespace migraphx {
inline namespace MIGRAPHX_INLINE_NS {
namespace cpu {

#ifdef MIGRAPHX_DISABLE_OMP

inline std::size_t max_threads() { return std::thread::hardware_concurrency(); }

template <class F>
void parallel_for_impl(std::size_t n, std::size_t threadsize, F f)
{
    if(threadsize <= 1)
    {
        f(std::size_t{0}, n);
    }
    else
    {
        std::vector<joinable_thread> threads(threadsize);
// Using const here causes gcc 5 to ICE
#if(!defined(__GNUC__) || __GNUC__ != 5)
        const
#endif
            std::size_t grainsize = std::ceil(static_cast<double>(n) / threads.size());

        std::size_t work = 0;
        std::generate(threads.begin(), threads.end(), [=, &work] {
            auto result =
                joinable_thread([=]() mutable { f(work, std::min(n, work + grainsize)); });
            work += grainsize;
            return result;
        });
        // cppcheck-suppress unsignedLessThanZero
        assert(work >= n);
    }
}
#else

inline std::size_t max_threads() { return omp_get_max_threads(); }

template <class F>
void parallel_for_impl(std::size_t n, std::size_t threadsize, F f)
{
    if(threadsize <= 1)
    {
        f(std::size_t{0}, n);
    }
    else
    {
        std::size_t grainsize = std::ceil(static_cast<double>(n) / threadsize);
#pragma omp parallel for num_threads(threadsize) schedule(static, 1) private(grainsize, n)
        for(std::size_t tid = 0; tid < threadsize; tid++)
        {
            std::size_t work = tid * grainsize;
            f(work, std::min(n, work + grainsize));
        }
    }
}
#endif
template <class F>
void parallel_for(std::size_t n, std::size_t min_grain, F f)
{
    const auto threadsize = std::min<std::size_t>(max_threads(), n / min_grain);
    parallel_for_impl(n, threadsize, f);
}

template <class F>
void parallel_for(std::size_t n, F f)
{
    const int min_grain = 8;
    parallel_for(n, min_grain, f);
}

} // namespace cpu
} // namespace MIGRAPHX_INLINE_NS
} // namespace migraphx

#endif
