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/* Copyright (c) the JPEG XL Project Authors. All rights reserved.
*
* Use of this source code is governed by a BSD-style
* license that can be found in the LICENSE file.
*/
/** @addtogroup libjxl_threads
* @{
* @file thread_parallel_runner.h
* @brief implementation using std::thread of a ::JxlParallelRunner.
*/
/** Implementation of JxlParallelRunner than can be used to enable
* multithreading when using the JPEG XL library. This uses std::thread
* internally and related synchronization functions. The number of threads
* created is fixed at construction time and the threads are re-used for every
* ThreadParallelRunner::Runner call. Only one concurrent
* JxlThreadParallelRunner call per instance is allowed at a time.
*
* This is a scalable, lower-overhead thread pool runner, especially suitable
* for data-parallel computations in the fork-join model, where clients need to
* know when all tasks have completed.
*
* This thread pool can efficiently load-balance millions of tasks using an
* atomic counter, thus avoiding per-task virtual or system calls. With 48
* hyperthreads and 1M tasks that add to an atomic counter, overall runtime is
* 10-20x higher when using std::async, and ~200x for a queue-based thread
*/
#ifndef JXL_THREAD_PARALLEL_RUNNER_H_
#define JXL_THREAD_PARALLEL_RUNNER_H_
#include <jxl/jxl_threads_export.h>
#include <jxl/memory_manager.h>
#include <jxl/parallel_runner.h>
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#ifdef __cplusplus
extern "C" {
#endif
/** Parallel runner internally using std::thread. Use as @ref JxlParallelRunner.
*/
JXL_THREADS_EXPORT JxlParallelRetCode JxlThreadParallelRunner(
void* runner_opaque, void* jpegxl_opaque, JxlParallelRunInit init,
JxlParallelRunFunction func, uint32_t start_range, uint32_t end_range);
/** Creates the runner for @ref JxlThreadParallelRunner. Use as the opaque
* runner.
*/
JXL_THREADS_EXPORT void* JxlThreadParallelRunnerCreate(
const JxlMemoryManager* memory_manager, size_t num_worker_threads);
/** Destroys the runner created by @ref JxlThreadParallelRunnerCreate.
*/
JXL_THREADS_EXPORT void JxlThreadParallelRunnerDestroy(void* runner_opaque);
/** Returns a default num_worker_threads value for
* @ref JxlThreadParallelRunnerCreate.
*/
JXL_THREADS_EXPORT size_t JxlThreadParallelRunnerDefaultNumWorkerThreads(void);
#ifdef __cplusplus
}
#endif
#endif /* JXL_THREAD_PARALLEL_RUNNER_H_ */
/** @}*/