    // Copyright (C) 2013  Davis E. King (davis@dlib.net)
    // License: Boost Software License   See LICENSE.txt for the full license.
    #ifndef DLIB_PARALLEL_FoR_Hh_
    #define DLIB_PARALLEL_FoR_Hh_

    #include "parallel_for_extension_abstract.h"
    #include "thread_pool_extension.h"
    #include "../console_progress_indicator.h"
    #include "async.h"

    namespace dlib
    {

    // ----------------------------------------------------------------------------------------

        namespace impl
        {

            template <typename T>
            class helper_parallel_for
            {
            public:
                helper_parallel_for (
                    T& obj_,
                    void (T::*funct_)(long)
                ) :
                    obj(obj_),
                    funct(funct_)
                {}

                T& obj;
                void (T::*funct)(long);

                void process_block (long begin, long end)
                {
                    for (long i = begin; i < end; ++i)
                        (obj.*funct)(i);
                }
            };

            template <typename T>
            class helper_parallel_for_funct
            {
            public:
                helper_parallel_for_funct (
                    const T& funct_
                ) : funct(funct_) {}

                const T& funct;

                void run(long i)
                {
                    funct(i);
                }
            };

            template <typename T>
            class helper_parallel_for_funct2
            {
            public:
                helper_parallel_for_funct2 (
                    const T& funct_
                ) : funct(funct_) {}

                const T& funct;

                void run(long begin, long end)
                {
                    funct(begin, end);
                }
            };
        }

    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------

        template <typename T>
        void parallel_for_blocked (
            thread_pool& tp,
            long begin,
            long end,
            T& obj,
            void (T::*funct)(long, long),
            long chunks_per_thread = 8
        )
        {
            // make sure requires clause is not broken
            DLIB_ASSERT(begin <= end && chunks_per_thread > 0,
                "\t void parallel_for_blocked()"
                << "\n\t Invalid inputs were given to this function"
                << "\n\t begin: " << begin
                << "\n\t end:   " << end
                << "\n\t chunks_per_thread: " << chunks_per_thread
                );

            if (tp.num_threads_in_pool() != 0)
            {
                const long num = end-begin;
                const long num_workers = static_cast<long>(tp.num_threads_in_pool());
                // How many samples to process in a single task (aim for chunks_per_thread jobs per worker)
                const long block_size = std::max(1L, num/(num_workers*chunks_per_thread));
                for (long i = 0; i < num; i+=block_size)
                {
                    tp.add_task(obj, funct, begin+i, begin+std::min(i+block_size, num));
                }
                tp.wait_for_all_tasks();
            }
            else
            {
                // Since there aren't any threads in the pool we might as well just invoke
                // the function directly since that's all the thread_pool object would do.
                // But doing it ourselves skips a mutex lock.
                (obj.*funct)(begin, end);
            }
        }

    // ----------------------------------------------------------------------------------------

        template <typename T>
        void parallel_for_blocked (
            unsigned long num_threads,
            long begin,
            long end,
            T& obj,
            void (T::*funct)(long, long),
            long chunks_per_thread = 8
        )
        {
            // make sure requires clause is not broken
            DLIB_ASSERT(begin <= end && chunks_per_thread > 0,
                "\t void parallel_for_blocked()"
                << "\n\t Invalid inputs were given to this function"
                << "\n\t begin: " << begin
                << "\n\t end:   " << end
                << "\n\t chunks_per_thread: " << chunks_per_thread
                );

            thread_pool tp(num_threads);
            parallel_for_blocked(tp, begin, end, obj, funct, chunks_per_thread);
        }

    // ----------------------------------------------------------------------------------------

        template <typename T>
        void parallel_for_blocked (
            thread_pool& tp,
            long begin,
            long end,
            const T& funct,
            long chunks_per_thread = 8
        )
        {
            // make sure requires clause is not broken
            DLIB_ASSERT(begin <= end && chunks_per_thread > 0,
                "\t void parallel_for_blocked()"
                << "\n\t Invalid inputs were given to this function"
                << "\n\t begin: " << begin
                << "\n\t end:   " << end
                << "\n\t chunks_per_thread: " << chunks_per_thread
                );

            impl::helper_parallel_for_funct2<T> helper(funct);
            parallel_for_blocked(tp, begin, end,  helper, &impl::helper_parallel_for_funct2<T>::run,  chunks_per_thread);
        }

    // ----------------------------------------------------------------------------------------

        template <typename T>
        void parallel_for_blocked (
            unsigned long num_threads,
            long begin,
            long end,
            const T& funct,
            long chunks_per_thread = 8
        )
        {
            // make sure requires clause is not broken
            DLIB_ASSERT(begin <= end && chunks_per_thread > 0,
                "\t void parallel_for_blocked()"
                << "\n\t Invalid inputs were given to this function"
                << "\n\t begin: " << begin
                << "\n\t end:   " << end
                << "\n\t chunks_per_thread: " << chunks_per_thread
                );

            thread_pool tp(num_threads);
            parallel_for_blocked(tp, begin, end, funct, chunks_per_thread);
        }

        template <typename T>
        void parallel_for_blocked (
            long begin,
            long end,
            const T& funct,
            long chunks_per_thread = 8
        )
        {
            parallel_for_blocked(default_thread_pool(), begin, end, funct, chunks_per_thread);
        }

    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------

        template <typename T>
        void parallel_for (
            thread_pool& tp,
            long begin,
            long end,
            T& obj,
            void (T::*funct)(long),
            long chunks_per_thread = 8
        )
        {
            // make sure requires clause is not broken
            DLIB_ASSERT(begin <= end && chunks_per_thread > 0,
                "\t void parallel_for()"
                << "\n\t Invalid inputs were given to this function"
                << "\n\t begin: " << begin
                << "\n\t end:   " << end
                << "\n\t chunks_per_thread: " << chunks_per_thread
                );

            impl::helper_parallel_for<T> helper(obj, funct);
            parallel_for_blocked(tp, begin, end, helper, &impl::helper_parallel_for<T>::process_block, chunks_per_thread);
        }

    // ----------------------------------------------------------------------------------------

        template <typename T>
        void parallel_for (
            unsigned long num_threads,
            long begin,
            long end,
            T& obj,
            void (T::*funct)(long),
            long chunks_per_thread = 8
        )
        {
            // make sure requires clause is not broken
            DLIB_ASSERT(begin <= end && chunks_per_thread > 0,
                "\t void parallel_for()"
                << "\n\t Invalid inputs were given to this function"
                << "\n\t begin: " << begin
                << "\n\t end:   " << end
                << "\n\t chunks_per_thread: " << chunks_per_thread
                );

            thread_pool tp(num_threads);
            parallel_for(tp, begin, end, obj, funct, chunks_per_thread);
        }

    // ----------------------------------------------------------------------------------------

        template <typename T>
        void parallel_for (
            thread_pool& tp,
            long begin,
            long end,
            const T& funct,
            long chunks_per_thread = 8
        )
        {
            // make sure requires clause is not broken
            DLIB_ASSERT(begin <= end && chunks_per_thread > 0,
                "\t void parallel_for()"
                << "\n\t Invalid inputs were given to this function"
                << "\n\t begin: " << begin
                << "\n\t end:   " << end
                << "\n\t chunks_per_thread: " << chunks_per_thread
                );

            impl::helper_parallel_for_funct<T> helper(funct);
            parallel_for(tp, begin, end,  helper, &impl::helper_parallel_for_funct<T>::run,  chunks_per_thread);
        }

    // ----------------------------------------------------------------------------------------

        template <typename T>
        void parallel_for (
            unsigned long num_threads,
            long begin,
            long end,
            const T& funct,
            long chunks_per_thread = 8
        )
        {
            // make sure requires clause is not broken
            DLIB_ASSERT(begin <= end && chunks_per_thread > 0,
                "\t void parallel_for()"
                << "\n\t Invalid inputs were given to this function"
                << "\n\t begin: " << begin
                << "\n\t end:   " << end
                << "\n\t chunks_per_thread: " << chunks_per_thread
                );

            thread_pool tp(num_threads);
            parallel_for(tp, begin, end, funct, chunks_per_thread);
        }

    // ----------------------------------------------------------------------------------------

        template <typename T>
        void parallel_for (
            long begin,
            long end,
            const T& funct,
            long chunks_per_thread = 8
        )
        {
            parallel_for(default_thread_pool(), begin, end, funct, chunks_per_thread);
        }

    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------

        namespace impl
        {
            template <typename T>
            class parfor_verbose_helper
            {
            public:
                parfor_verbose_helper(T& obj_, void (T::*funct_)(long), long begin, long end) :
                    obj(obj_), funct(funct_), pbar(end-begin)
                {
                    count = 0;
                    wrote_to_screen = pbar.print_status(0);
                }

                ~parfor_verbose_helper()
                {
                    if (wrote_to_screen)
                        std::cout << std::endl;
                }

                mutable long count;
                T& obj;
                void (T::*funct)(long);
                mutable console_progress_indicator pbar;
                mutable bool wrote_to_screen;
                mutex m;

                void operator()(long i) const
                {
                    (obj.*funct)(i);
                    {
                        auto_mutex lock(m);
                        wrote_to_screen = pbar.print_status(++count) || wrote_to_screen;
                    }
                }

            };

            template <typename T>
            class parfor_verbose_helper3
            {
            public:
                parfor_verbose_helper3(T& obj_, void (T::*funct_)(long,long), long begin, long end) :
                    obj(obj_), funct(funct_), pbar(end-begin)
                {
                    count = 0;
                    wrote_to_screen = pbar.print_status(0);
                }

                ~parfor_verbose_helper3()
                {
                    if (wrote_to_screen)
                        std::cout << std::endl;
                }

                mutable long count;
                T& obj;
                void (T::*funct)(long,long);
                mutable console_progress_indicator pbar;
                mutable bool wrote_to_screen;
                mutex m;

                void operator()(long begin, long end) const
                {
                    (obj.*funct)(begin, end);
                    {
                        auto_mutex lock(m);
                        count += end-begin;
                        wrote_to_screen = pbar.print_status(count) || wrote_to_screen;
                    }
                }
            };

            template <typename T>
            class parfor_verbose_helper2
            {
            public:
                parfor_verbose_helper2(const T& obj_, long begin, long end) : obj(obj_), pbar(end-begin)
                {
                    count = 0;
                    wrote_to_screen = pbar.print_status(0);
                }

                ~parfor_verbose_helper2()
                {
                    if (wrote_to_screen)
                        std::cout << std::endl;
                }

                mutable long count;
                const T& obj;
                mutable console_progress_indicator pbar;
                mutable bool wrote_to_screen;
                mutex m;

                void operator()(long i) const
                {
                    obj(i);
                    {
                        auto_mutex lock(m);
                        wrote_to_screen = pbar.print_status(++count) || wrote_to_screen;
                    }
                }

                void operator()(long begin, long end) const
                {
                    obj(begin, end);
                    {
                        auto_mutex lock(m);
                        count += end-begin;
                        wrote_to_screen = pbar.print_status(count) || wrote_to_screen;
                    }
                }
            };
        }

        template <typename T>
        void parallel_for_verbose (
            thread_pool& tp,
            long begin,
            long end,
            T& obj,
            void (T::*funct)(long),
            long chunks_per_thread = 8
        )
        {
            // make sure requires clause is not broken
            DLIB_ASSERT(begin <= end && chunks_per_thread > 0,
                "\t void parallel_for_verbose()"
                << "\n\t Invalid inputs were given to this function"
                << "\n\t begin: " << begin
                << "\n\t end:   " << end
                << "\n\t chunks_per_thread: " << chunks_per_thread
                );

            impl::parfor_verbose_helper<T> helper(obj, funct, begin, end);
            parallel_for(tp, begin, end, helper, chunks_per_thread);
        }

    // ----------------------------------------------------------------------------------------

        template <typename T>
        void parallel_for_verbose (
            unsigned long num_threads,
            long begin,
            long end,
            T& obj,
            void (T::*funct)(long),
            long chunks_per_thread = 8
        )
        {
            // make sure requires clause is not broken
            DLIB_ASSERT(begin <= end && chunks_per_thread > 0,
                "\t void parallel_for_verbose()"
                << "\n\t Invalid inputs were given to this function"
                << "\n\t begin: " << begin
                << "\n\t end:   " << end
                << "\n\t chunks_per_thread: " << chunks_per_thread
                );

            impl::parfor_verbose_helper<T> helper(obj, funct, begin, end);
            parallel_for(num_threads, begin, end, helper, chunks_per_thread);
        }

    // ----------------------------------------------------------------------------------------

        template <typename T>
        void parallel_for_verbose (
            thread_pool& tp,
            long begin,
            long end,
            const T& funct,
            long chunks_per_thread = 8
        )
        {
            // make sure requires clause is not broken
            DLIB_ASSERT(begin <= end && chunks_per_thread > 0,
                "\t void parallel_for_verbose()"
                << "\n\t Invalid inputs were given to this function"
                << "\n\t begin: " << begin
                << "\n\t end:   " << end
                << "\n\t chunks_per_thread: " << chunks_per_thread
                );

            impl::parfor_verbose_helper2<T> helper(funct, begin, end);
            parallel_for(tp, begin, end,  helper, chunks_per_thread);
        }

    // ----------------------------------------------------------------------------------------

        template <typename T>
        void parallel_for_verbose (
            unsigned long num_threads,
            long begin,
            long end,
            const T& funct,
            long chunks_per_thread = 8
        )
        {
            // make sure requires clause is not broken
            DLIB_ASSERT(begin <= end && chunks_per_thread > 0,
                "\t void parallel_for_verbose()"
                << "\n\t Invalid inputs were given to this function"
                << "\n\t begin: " << begin
                << "\n\t end:   " << end
                << "\n\t chunks_per_thread: " << chunks_per_thread
                );

            impl::parfor_verbose_helper2<T> helper(funct, begin, end);
            parallel_for(num_threads, begin, end, helper, chunks_per_thread);
        }

    // ----------------------------------------------------------------------------------------

        template <typename T>
        void parallel_for_verbose (
            long begin,
            long end,
            const T& funct,
            long chunks_per_thread = 8
        )
        {
            // make sure requires clause is not broken
            DLIB_ASSERT(begin <= end && chunks_per_thread > 0,
                "\t void parallel_for_verbose()"
                << "\n\t Invalid inputs were given to this function"
                << "\n\t begin: " << begin
                << "\n\t end:   " << end
                << "\n\t chunks_per_thread: " << chunks_per_thread
                );

            impl::parfor_verbose_helper2<T> helper(funct, begin, end);
            parallel_for(begin, end, helper, chunks_per_thread);
        }

    // ----------------------------------------------------------------------------------------

        template <typename T>
        void parallel_for_blocked_verbose (
            thread_pool& tp,
            long begin,
            long end,
            T& obj,
            void (T::*funct)(long,long),
            long chunks_per_thread = 8
        )
        {
            // make sure requires clause is not broken
            DLIB_ASSERT(begin <= end && chunks_per_thread > 0,
                "\t void parallel_for_blocked_verbose()"
                << "\n\t Invalid inputs were given to this function"
                << "\n\t begin: " << begin
                << "\n\t end:   " << end
                << "\n\t chunks_per_thread: " << chunks_per_thread
                );

            impl::parfor_verbose_helper3<T> helper(obj, funct, begin, end);
            parallel_for_blocked(tp, begin, end, helper, chunks_per_thread);
        }

    // ----------------------------------------------------------------------------------------

        template <typename T>
        void parallel_for_blocked_verbose (
            unsigned long num_threads,
            long begin,
            long end,
            T& obj,
            void (T::*funct)(long,long),
            long chunks_per_thread = 8
        )
        {
            // make sure requires clause is not broken
            DLIB_ASSERT(begin <= end && chunks_per_thread > 0,
                "\t void parallel_for_blocked_verbose()"
                << "\n\t Invalid inputs were given to this function"
                << "\n\t begin: " << begin
                << "\n\t end:   " << end
                << "\n\t chunks_per_thread: " << chunks_per_thread
                );

            impl::parfor_verbose_helper3<T> helper(obj, funct, begin, end);
            parallel_for_blocked(num_threads, begin, end, helper, chunks_per_thread);
        }

    // ----------------------------------------------------------------------------------------

        template <typename T>
        void parallel_for_blocked_verbose (
            thread_pool& tp,
            long begin,
            long end,
            const T& funct,
            long chunks_per_thread = 8
        )
        {
            // make sure requires clause is not broken
            DLIB_ASSERT(begin <= end && chunks_per_thread > 0,
                "\t void parallel_for_blocked_verbose()"
                << "\n\t Invalid inputs were given to this function"
                << "\n\t begin: " << begin
                << "\n\t end:   " << end
                << "\n\t chunks_per_thread: " << chunks_per_thread
                );

            impl::parfor_verbose_helper2<T> helper(funct, begin, end);
            parallel_for_blocked(tp, begin, end,  helper, chunks_per_thread);
        }

    // ----------------------------------------------------------------------------------------

        template <typename T>
        void parallel_for_blocked_verbose (
            unsigned long num_threads,
            long begin,
            long end,
            const T& funct,
            long chunks_per_thread = 8
        )
        {
            // make sure requires clause is not broken
            DLIB_ASSERT(begin <= end && chunks_per_thread > 0,
                "\t void parallel_for_blocked_verbose()"
                << "\n\t Invalid inputs were given to this function"
                << "\n\t begin: " << begin
                << "\n\t end:   " << end
                << "\n\t chunks_per_thread: " << chunks_per_thread
                );

            impl::parfor_verbose_helper2<T> helper(funct, begin, end);
            parallel_for_blocked(num_threads, begin, end, helper, chunks_per_thread);
        }

    // ----------------------------------------------------------------------------------------

        template <typename T>
        void parallel_for_blocked_verbose (
            long begin,
            long end,
            const T& funct,
            long chunks_per_thread = 8
        )
        {
            // make sure requires clause is not broken
            DLIB_ASSERT(begin <= end && chunks_per_thread > 0,
                "\t void parallel_for_blocked_verbose()"
                << "\n\t Invalid inputs were given to this function"
                << "\n\t begin: " << begin
                << "\n\t end:   " << end
                << "\n\t chunks_per_thread: " << chunks_per_thread
                );

            impl::parfor_verbose_helper2<T> helper(funct, begin, end);
            parallel_for_blocked(begin, end, helper, chunks_per_thread);
        }

    // ----------------------------------------------------------------------------------------

    }

    #endif // DLIB_PARALLEL_FoR_Hh_