| //===- llvm/Support/Parallel.h - Parallel algorithms ----------------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_SUPPORT_PARALLEL_H |
| #define LLVM_SUPPORT_PARALLEL_H |
| |
| #include "llvm/ADT/STLExtras.h" |
| #include "llvm/Config/llvm-config.h" |
| #include "llvm/Support/MathExtras.h" |
| |
| #include <algorithm> |
| #include <condition_variable> |
| #include <functional> |
| #include <mutex> |
| |
| #if defined(_MSC_VER) && LLVM_ENABLE_THREADS |
| #pragma warning(push) |
| #pragma warning(disable : 4530) |
| #include <concrt.h> |
| #include <ppl.h> |
| #pragma warning(pop) |
| #endif |
| |
| namespace llvm { |
| |
| namespace parallel { |
| struct sequential_execution_policy {}; |
| struct parallel_execution_policy {}; |
| |
| template <typename T> |
| struct is_execution_policy |
| : public std::integral_constant< |
| bool, llvm::is_one_of<T, sequential_execution_policy, |
| parallel_execution_policy>::value> {}; |
| |
| constexpr sequential_execution_policy seq{}; |
| constexpr parallel_execution_policy par{}; |
| |
| namespace detail { |
| |
| #if LLVM_ENABLE_THREADS |
| |
| class Latch { |
| uint32_t Count; |
| mutable std::mutex Mutex; |
| mutable std::condition_variable Cond; |
| |
| public: |
| explicit Latch(uint32_t Count = 0) : Count(Count) {} |
| ~Latch() { sync(); } |
| |
| void inc() { |
| std::unique_lock<std::mutex> lock(Mutex); |
| ++Count; |
| } |
| |
| void dec() { |
| std::unique_lock<std::mutex> lock(Mutex); |
| if (--Count == 0) |
| Cond.notify_all(); |
| } |
| |
| void sync() const { |
| std::unique_lock<std::mutex> lock(Mutex); |
| Cond.wait(lock, [&] { return Count == 0; }); |
| } |
| }; |
| |
| class TaskGroup { |
| Latch L; |
| |
| public: |
| void spawn(std::function<void()> f); |
| |
| void sync() const { L.sync(); } |
| }; |
| |
| #if defined(_MSC_VER) |
| template <class RandomAccessIterator, class Comparator> |
| void parallel_sort(RandomAccessIterator Start, RandomAccessIterator End, |
| const Comparator &Comp) { |
| concurrency::parallel_sort(Start, End, Comp); |
| } |
| template <class IterTy, class FuncTy> |
| void parallel_for_each(IterTy Begin, IterTy End, FuncTy Fn) { |
| concurrency::parallel_for_each(Begin, End, Fn); |
| } |
| |
| template <class IndexTy, class FuncTy> |
| void parallel_for_each_n(IndexTy Begin, IndexTy End, FuncTy Fn) { |
| concurrency::parallel_for(Begin, End, Fn); |
| } |
| |
| #else |
| const ptrdiff_t MinParallelSize = 1024; |
| |
| /// \brief Inclusive median. |
| template <class RandomAccessIterator, class Comparator> |
| RandomAccessIterator medianOf3(RandomAccessIterator Start, |
| RandomAccessIterator End, |
| const Comparator &Comp) { |
| RandomAccessIterator Mid = Start + (std::distance(Start, End) / 2); |
| return Comp(*Start, *(End - 1)) |
| ? (Comp(*Mid, *(End - 1)) ? (Comp(*Start, *Mid) ? Mid : Start) |
| : End - 1) |
| : (Comp(*Mid, *Start) ? (Comp(*(End - 1), *Mid) ? Mid : End - 1) |
| : Start); |
| } |
| |
| template <class RandomAccessIterator, class Comparator> |
| void parallel_quick_sort(RandomAccessIterator Start, RandomAccessIterator End, |
| const Comparator &Comp, TaskGroup &TG, size_t Depth) { |
| // Do a sequential sort for small inputs. |
| if (std::distance(Start, End) < detail::MinParallelSize || Depth == 0) { |
| std::sort(Start, End, Comp); |
| return; |
| } |
| |
| // Partition. |
| auto Pivot = medianOf3(Start, End, Comp); |
| // Move Pivot to End. |
| std::swap(*(End - 1), *Pivot); |
| Pivot = std::partition(Start, End - 1, [&Comp, End](decltype(*Start) V) { |
| return Comp(V, *(End - 1)); |
| }); |
| // Move Pivot to middle of partition. |
| std::swap(*Pivot, *(End - 1)); |
| |
| // Recurse. |
| TG.spawn([=, &Comp, &TG] { |
| parallel_quick_sort(Start, Pivot, Comp, TG, Depth - 1); |
| }); |
| parallel_quick_sort(Pivot + 1, End, Comp, TG, Depth - 1); |
| } |
| |
| template <class RandomAccessIterator, class Comparator> |
| void parallel_sort(RandomAccessIterator Start, RandomAccessIterator End, |
| const Comparator &Comp) { |
| TaskGroup TG; |
| parallel_quick_sort(Start, End, Comp, TG, |
| llvm::Log2_64(std::distance(Start, End)) + 1); |
| } |
| |
| template <class IterTy, class FuncTy> |
| void parallel_for_each(IterTy Begin, IterTy End, FuncTy Fn) { |
| // TaskGroup has a relatively high overhead, so we want to reduce |
| // the number of spawn() calls. We'll create up to 1024 tasks here. |
| // (Note that 1024 is an arbitrary number. This code probably needs |
| // improving to take the number of available cores into account.) |
| ptrdiff_t TaskSize = std::distance(Begin, End) / 1024; |
| if (TaskSize == 0) |
| TaskSize = 1; |
| |
| TaskGroup TG; |
| while (TaskSize < std::distance(Begin, End)) { |
| TG.spawn([=, &Fn] { std::for_each(Begin, Begin + TaskSize, Fn); }); |
| Begin += TaskSize; |
| } |
| std::for_each(Begin, End, Fn); |
| } |
| |
| template <class IndexTy, class FuncTy> |
| void parallel_for_each_n(IndexTy Begin, IndexTy End, FuncTy Fn) { |
| ptrdiff_t TaskSize = (End - Begin) / 1024; |
| if (TaskSize == 0) |
| TaskSize = 1; |
| |
| TaskGroup TG; |
| IndexTy I = Begin; |
| for (; I + TaskSize < End; I += TaskSize) { |
| TG.spawn([=, &Fn] { |
| for (IndexTy J = I, E = I + TaskSize; J != E; ++J) |
| Fn(J); |
| }); |
| } |
| for (IndexTy J = I; J < End; ++J) |
| Fn(J); |
| } |
| |
| #endif |
| |
| #endif |
| |
| template <typename Iter> |
| using DefComparator = |
| std::less<typename std::iterator_traits<Iter>::value_type>; |
| |
| } // namespace detail |
| |
| // sequential algorithm implementations. |
| template <class Policy, class RandomAccessIterator, |
| class Comparator = detail::DefComparator<RandomAccessIterator>> |
| void sort(Policy policy, RandomAccessIterator Start, RandomAccessIterator End, |
| const Comparator &Comp = Comparator()) { |
| static_assert(is_execution_policy<Policy>::value, |
| "Invalid execution policy!"); |
| std::sort(Start, End, Comp); |
| } |
| |
| template <class Policy, class IterTy, class FuncTy> |
| void for_each(Policy policy, IterTy Begin, IterTy End, FuncTy Fn) { |
| static_assert(is_execution_policy<Policy>::value, |
| "Invalid execution policy!"); |
| std::for_each(Begin, End, Fn); |
| } |
| |
| template <class Policy, class IndexTy, class FuncTy> |
| void for_each_n(Policy policy, IndexTy Begin, IndexTy End, FuncTy Fn) { |
| static_assert(is_execution_policy<Policy>::value, |
| "Invalid execution policy!"); |
| for (IndexTy I = Begin; I != End; ++I) |
| Fn(I); |
| } |
| |
| // Parallel algorithm implementations, only available when LLVM_ENABLE_THREADS |
| // is true. |
| #if LLVM_ENABLE_THREADS |
| template <class RandomAccessIterator, |
| class Comparator = detail::DefComparator<RandomAccessIterator>> |
| void sort(parallel_execution_policy policy, RandomAccessIterator Start, |
| RandomAccessIterator End, const Comparator &Comp = Comparator()) { |
| detail::parallel_sort(Start, End, Comp); |
| } |
| |
| template <class IterTy, class FuncTy> |
| void for_each(parallel_execution_policy policy, IterTy Begin, IterTy End, |
| FuncTy Fn) { |
| detail::parallel_for_each(Begin, End, Fn); |
| } |
| |
| template <class IndexTy, class FuncTy> |
| void for_each_n(parallel_execution_policy policy, IndexTy Begin, IndexTy End, |
| FuncTy Fn) { |
| detail::parallel_for_each_n(Begin, End, Fn); |
| } |
| #endif |
| |
| } // namespace parallel |
| } // namespace llvm |
| |
| #endif // LLVM_SUPPORT_PARALLEL_H |