76 lines
2.4 KiB
C++
76 lines
2.4 KiB
C++
// Copyright 2010-2025 Google LLC
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef ORTOOLS_BASE_THREADPOOL_H_
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#define ORTOOLS_BASE_THREADPOOL_H_
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#include <cstddef>
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#include <deque>
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#include <optional>
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#include <thread> // NOLINT
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#include <vector>
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#include "absl/base/nullability.h"
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#include "absl/base/thread_annotations.h"
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#include "absl/functional/any_invocable.h"
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#include "absl/strings/string_view.h"
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#include "absl/synchronization/mutex.h"
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namespace operations_research {
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class ThreadPool {
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public:
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explicit ThreadPool(int num_threads);
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ThreadPool(absl::string_view prefix, int num_threads);
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~ThreadPool();
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void Schedule(absl::AnyInvocable<void() &&> callback);
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private:
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// Waiter for a single thread.
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struct Waiter {
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absl::CondVar cv; // signalled when there is work to do
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};
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// Spawn a single new worker thread.
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//
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// REQUIRES: threads_.size() < max_threads_
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void SpawnThread() ABSL_EXCLUSIVE_LOCKS_REQUIRED(mutex_);
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void RunWorker();
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// Removes the oldest element from the queue and returns it. Causes the
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// current thread to wait for producers if the queue is empty. Returns
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// an empty `std::optional` if the thread pool is shutting down.
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std::optional<absl::AnyInvocable<void() &&>> DequeueWork()
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ABSL_LOCKS_EXCLUDED(mutex_);
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// Signals a waiter if there is one, or spawns a thread to try to add a new
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// waiter.
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//
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// REQUIRES: !queue_.empty()
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void SignalWaiter() ABSL_EXCLUSIVE_LOCKS_REQUIRED(mutex_);
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mutable absl::Mutex mutex_;
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absl::CondVar wait_nonfull_ ABSL_GUARDED_BY(mutex_);
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std::vector<Waiter* absl_nonnull> waiters_ ABSL_GUARDED_BY(mutex_);
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const size_t max_threads_;
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std::deque<absl::AnyInvocable<void() &&>> queue_;
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bool stopping_ ABSL_GUARDED_BY(mutex_) = false;
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size_t running_threads_ ABSL_GUARDED_BY(mutex_) = 0;
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std::vector<std::thread> threads_ ABSL_GUARDED_BY(mutex_);
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};
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} // namespace operations_research
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#endif // ORTOOLS_BASE_THREADPOOL_H_
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