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#pragma once
#ifdef __GNUC__
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-parameter"
#endif
//===-- llvm/Support/ThreadPool.h - A ThreadPool implementation -*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines a crude C++11 based thread pool.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_SUPPORT_THREAD_POOL_H
#define LLVM_SUPPORT_THREAD_POOL_H
#include "llvm/Config/llvm-config.h"
#include "llvm/Support/Threading.h"
#include "llvm/Support/thread.h"
#include <future>
#include <atomic>
#include <condition_variable>
#include <functional>
#include <memory>
#include <mutex>
#include <queue>
#include <utility>
namespace llvm {
/// A ThreadPool for asynchronous parallel execution on a defined number of
/// threads.
///
/// The pool keeps a vector of threads alive, waiting on a condition variable
/// for some work to become available.
class ThreadPool {
public:
using TaskTy = std::function<void()>;
using PackagedTaskTy = std::packaged_task<void()>;
/// Construct a pool using the hardware strategy \p S for mapping hardware
/// execution resources (threads, cores, CPUs)
/// Defaults to using the maximum execution resources in the system, but
/// accounting for the affinity mask.
ThreadPool(ThreadPoolStrategy S = hardware_concurrency());
/// Blocking destructor: the pool will wait for all the threads to complete.
~ThreadPool();
/// Asynchronous submission of a task to the pool. The returned future can be
/// used to wait for the task to finish and is *non-blocking* on destruction.
template <typename Function, typename... Args>
inline std::shared_future<void> async(Function &&F, Args &&... ArgList) {
auto Task =
std::bind(std::forward<Function>(F), std::forward<Args>(ArgList)...);
return asyncImpl(std::move(Task));
}
/// Asynchronous submission of a task to the pool. The returned future can be
/// used to wait for the task to finish and is *non-blocking* on destruction.
template <typename Function>
inline std::shared_future<void> async(Function &&F) {
return asyncImpl(std::forward<Function>(F));
}
/// Blocking wait for all the threads to complete and the queue to be empty.
/// It is an error to try to add new tasks while blocking on this call.
void wait();
unsigned getThreadCount() const { return ThreadCount; }
private:
bool workCompletedUnlocked() { return !ActiveThreads && Tasks.empty(); }
/// Asynchronous submission of a task to the pool. The returned future can be
/// used to wait for the task to finish and is *non-blocking* on destruction.
std::shared_future<void> asyncImpl(TaskTy F);
/// Threads in flight
std::vector<llvm::thread> Threads;
/// Tasks waiting for execution in the pool.
std::queue<PackagedTaskTy> Tasks;
/// Locking and signaling for accessing the Tasks queue.
std::mutex QueueLock;
std::condition_variable QueueCondition;
/// Signaling for job completion
std::condition_variable CompletionCondition;
/// Keep track of the number of thread actually busy
unsigned ActiveThreads = 0;
#if LLVM_ENABLE_THREADS // avoids warning for unused variable
/// Signal for the destruction of the pool, asking thread to exit.
bool EnableFlag = true;
#endif
unsigned ThreadCount;
};
}
#endif // LLVM_SUPPORT_THREAD_POOL_H
#ifdef __GNUC__
#pragma GCC diagnostic pop
#endif
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