387 lines
12 KiB
C++
387 lines
12 KiB
C++
// Copyright 2009-2020 Intel Corporation
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// SPDX-License-Identifier: Apache-2.0
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#pragma once
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#include "../sys/platform.h"
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#include "../sys/alloc.h"
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#include "../sys/barrier.h"
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#include "../sys/thread.h"
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#include "../sys/mutex.h"
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#include "../sys/condition.h"
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#include "../sys/ref.h"
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#include "../sys/atomic.h"
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#include "../math/range.h"
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#include "../../include/embree3/rtcore.h"
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#include <list>
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namespace embree
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{
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/* The tasking system exports some symbols to be used by the tutorials. Thus we
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hide is also in the API namespace when requested. */
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RTC_NAMESPACE_BEGIN
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struct TaskScheduler : public RefCount
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{
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ALIGNED_STRUCT_(64);
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friend class Device;
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static const size_t TASK_STACK_SIZE = 4*1024; //!< task structure stack
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static const size_t CLOSURE_STACK_SIZE = 512*1024; //!< stack for task closures
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struct Thread;
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/*! virtual interface for all tasks */
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struct TaskFunction {
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virtual void execute() = 0;
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};
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/*! builds a task interface from a closure */
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template<typename Closure>
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struct ClosureTaskFunction : public TaskFunction
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{
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Closure closure;
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__forceinline ClosureTaskFunction (const Closure& closure) : closure(closure) {}
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void execute() { closure(); };
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};
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struct __aligned(64) Task
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{
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/*! states a task can be in */
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enum { DONE, INITIALIZED };
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/*! switch from one state to another */
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__forceinline void switch_state(int from, int to)
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{
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__memory_barrier();
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MAYBE_UNUSED bool success = state.compare_exchange_strong(from,to);
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assert(success);
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}
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/*! try to switch from one state to another */
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__forceinline bool try_switch_state(int from, int to) {
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__memory_barrier();
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return state.compare_exchange_strong(from,to);
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}
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/*! increment/decrement dependency counter */
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void add_dependencies(int n) {
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dependencies+=n;
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}
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/*! initialize all tasks to DONE state by default */
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__forceinline Task()
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: state(DONE) {}
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/*! construction of new task */
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__forceinline Task (TaskFunction* closure, Task* parent, size_t stackPtr, size_t N)
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: dependencies(1), stealable(true), closure(closure), parent(parent), stackPtr(stackPtr), N(N)
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{
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if (parent) parent->add_dependencies(+1);
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switch_state(DONE,INITIALIZED);
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}
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/*! construction of stolen task, stealing thread will decrement initial dependency */
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__forceinline Task (TaskFunction* closure, Task* parent)
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: dependencies(1), stealable(false), closure(closure), parent(parent), stackPtr(-1), N(1)
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{
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switch_state(DONE,INITIALIZED);
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}
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/*! try to steal this task */
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bool try_steal(Task& child)
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{
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if (!stealable) return false;
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if (!try_switch_state(INITIALIZED,DONE)) return false;
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new (&child) Task(closure, this);
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return true;
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}
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/*! run this task */
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dll_export void run(Thread& thread);
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void run_internal(Thread& thread);
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public:
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std::atomic<int> state; //!< state this task is in
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std::atomic<int> dependencies; //!< dependencies to wait for
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std::atomic<bool> stealable; //!< true if task can be stolen
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TaskFunction* closure; //!< the closure to execute
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Task* parent; //!< parent task to signal when we are finished
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size_t stackPtr; //!< stack location where closure is stored
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size_t N; //!< approximative size of task
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};
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struct TaskQueue
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{
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TaskQueue ()
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: left(0), right(0), stackPtr(0) {}
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__forceinline void* alloc(size_t bytes, size_t align = 64)
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{
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size_t ofs = bytes + ((align - stackPtr) & (align-1));
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if (stackPtr + ofs > CLOSURE_STACK_SIZE)
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// -- GODOT start --
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// throw std::runtime_error("closure stack overflow");
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abort();
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// -- GODOT end --
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stackPtr += ofs;
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return &stack[stackPtr-bytes];
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}
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template<typename Closure>
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__forceinline void push_right(Thread& thread, const size_t size, const Closure& closure)
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{
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if (right >= TASK_STACK_SIZE)
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// -- GODOT start --
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// throw std::runtime_error("task stack overflow");
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abort();
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// -- GODOT end --
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/* allocate new task on right side of stack */
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size_t oldStackPtr = stackPtr;
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TaskFunction* func = new (alloc(sizeof(ClosureTaskFunction<Closure>))) ClosureTaskFunction<Closure>(closure);
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/* gcc 8 or later fails to compile without explicit .load() */
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new (&(tasks[right.load()])) Task(func,thread.task,oldStackPtr,size);
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right++;
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/* also move left pointer */
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if (left >= right-1) left = right-1;
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}
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dll_export bool execute_local(Thread& thread, Task* parent);
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bool execute_local_internal(Thread& thread, Task* parent);
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bool steal(Thread& thread);
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size_t getTaskSizeAtLeft();
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bool empty() { return right == 0; }
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public:
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/* task stack */
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Task tasks[TASK_STACK_SIZE];
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__aligned(64) std::atomic<size_t> left; //!< threads steal from left
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__aligned(64) std::atomic<size_t> right; //!< new tasks are added to the right
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/* closure stack */
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__aligned(64) char stack[CLOSURE_STACK_SIZE];
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size_t stackPtr;
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};
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/*! thread local structure for each thread */
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struct Thread
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{
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ALIGNED_STRUCT_(64);
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Thread (size_t threadIndex, const Ref<TaskScheduler>& scheduler)
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: threadIndex(threadIndex), task(nullptr), scheduler(scheduler) {}
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__forceinline size_t threadCount() {
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return scheduler->threadCounter;
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}
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size_t threadIndex; //!< ID of this thread
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TaskQueue tasks; //!< local task queue
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Task* task; //!< current active task
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Ref<TaskScheduler> scheduler; //!< pointer to task scheduler
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};
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/*! pool of worker threads */
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struct ThreadPool
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{
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ThreadPool (bool set_affinity);
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~ThreadPool ();
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/*! starts the threads */
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dll_export void startThreads();
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/*! sets number of threads to use */
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void setNumThreads(size_t numThreads, bool startThreads = false);
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/*! adds a task scheduler object for scheduling */
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dll_export void add(const Ref<TaskScheduler>& scheduler);
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/*! remove the task scheduler object again */
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dll_export void remove(const Ref<TaskScheduler>& scheduler);
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/*! returns number of threads of the thread pool */
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size_t size() const { return numThreads; }
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/*! main loop for all threads */
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void thread_loop(size_t threadIndex);
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private:
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std::atomic<size_t> numThreads;
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std::atomic<size_t> numThreadsRunning;
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bool set_affinity;
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std::atomic<bool> running;
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std::vector<thread_t> threads;
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private:
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MutexSys mutex;
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ConditionSys condition;
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std::list<Ref<TaskScheduler> > schedulers;
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};
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TaskScheduler ();
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~TaskScheduler ();
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/*! initializes the task scheduler */
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static void create(size_t numThreads, bool set_affinity, bool start_threads);
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/*! destroys the task scheduler again */
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static void destroy();
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/*! lets new worker threads join the tasking system */
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void join();
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void reset();
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/*! let a worker thread allocate a thread index */
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dll_export ssize_t allocThreadIndex();
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/*! wait for some number of threads available (threadCount includes main thread) */
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void wait_for_threads(size_t threadCount);
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/*! thread loop for all worker threads */
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// -- GODOT start --
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// std::exception_ptr thread_loop(size_t threadIndex);
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void thread_loop(size_t threadIndex);
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// -- GODOT end --
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/*! steals a task from a different thread */
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bool steal_from_other_threads(Thread& thread);
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template<typename Predicate, typename Body>
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static void steal_loop(Thread& thread, const Predicate& pred, const Body& body);
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/* spawn a new task at the top of the threads task stack */
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template<typename Closure>
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void spawn_root(const Closure& closure, size_t size = 1, bool useThreadPool = true)
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{
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if (useThreadPool) startThreads();
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size_t threadIndex = allocThreadIndex();
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std::unique_ptr<Thread> mthread(new Thread(threadIndex,this)); // too large for stack allocation
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Thread& thread = *mthread;
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assert(threadLocal[threadIndex].load() == nullptr);
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threadLocal[threadIndex] = &thread;
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Thread* oldThread = swapThread(&thread);
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thread.tasks.push_right(thread,size,closure);
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{
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Lock<MutexSys> lock(mutex);
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anyTasksRunning++;
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hasRootTask = true;
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condition.notify_all();
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}
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if (useThreadPool) addScheduler(this);
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while (thread.tasks.execute_local(thread,nullptr));
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anyTasksRunning--;
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if (useThreadPool) removeScheduler(this);
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threadLocal[threadIndex] = nullptr;
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swapThread(oldThread);
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/* remember exception to throw */
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std::exception_ptr except = nullptr;
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if (cancellingException != nullptr) except = cancellingException;
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/* wait for all threads to terminate */
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threadCounter--;
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while (threadCounter > 0) yield();
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cancellingException = nullptr;
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/* re-throw proper exception */
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if (except != nullptr)
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std::rethrow_exception(except);
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}
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/* spawn a new task at the top of the threads task stack */
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template<typename Closure>
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static __forceinline void spawn(size_t size, const Closure& closure)
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{
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Thread* thread = TaskScheduler::thread();
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if (likely(thread != nullptr)) thread->tasks.push_right(*thread,size,closure);
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else instance()->spawn_root(closure,size);
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}
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/* spawn a new task at the top of the threads task stack */
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template<typename Closure>
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static __forceinline void spawn(const Closure& closure) {
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spawn(1,closure);
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}
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/* spawn a new task set */
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template<typename Index, typename Closure>
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static void spawn(const Index begin, const Index end, const Index blockSize, const Closure& closure)
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{
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spawn(end-begin, [=]()
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{
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if (end-begin <= blockSize) {
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return closure(range<Index>(begin,end));
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}
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const Index center = (begin+end)/2;
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spawn(begin,center,blockSize,closure);
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spawn(center,end ,blockSize,closure);
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wait();
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});
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}
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/* work on spawned subtasks and wait until all have finished */
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dll_export static bool wait();
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/* returns the ID of the current thread */
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dll_export static size_t threadID();
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/* returns the index (0..threadCount-1) of the current thread */
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dll_export static size_t threadIndex();
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/* returns the total number of threads */
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dll_export static size_t threadCount();
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private:
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/* returns the thread local task list of this worker thread */
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dll_export static Thread* thread();
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/* sets the thread local task list of this worker thread */
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dll_export static Thread* swapThread(Thread* thread);
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/*! returns the taskscheduler object to be used by the master thread */
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dll_export static TaskScheduler* instance();
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/*! starts the threads */
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dll_export static void startThreads();
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/*! adds a task scheduler object for scheduling */
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dll_export static void addScheduler(const Ref<TaskScheduler>& scheduler);
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/*! remove the task scheduler object again */
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dll_export static void removeScheduler(const Ref<TaskScheduler>& scheduler);
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private:
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std::vector<atomic<Thread*>> threadLocal;
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std::atomic<size_t> threadCounter;
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std::atomic<size_t> anyTasksRunning;
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std::atomic<bool> hasRootTask;
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std::exception_ptr cancellingException;
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MutexSys mutex;
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ConditionSys condition;
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private:
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static size_t g_numThreads;
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static __thread TaskScheduler* g_instance;
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static __thread Thread* thread_local_thread;
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static ThreadPool* threadPool;
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};
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RTC_NAMESPACE_END
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#if defined(RTC_NAMESPACE)
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using RTC_NAMESPACE::TaskScheduler;
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#endif
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}
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