Simple thread pool that executes tasks in a fixed number of worker threads. More...

#include <ThreadPool.h>

Public Types
using	Task = ThreadPoolTask

Public Member Functions
Result	create (size_t workerThreads)
	Create a thread pool with the requested number of worker threads.

Result	destroy ()
	Destroy the thread pool created previously with ThreadPool::create.

Result	queueTask (Task &task)
	Queue a task (that should not be already in use)

Result	waitForAllTasks ()
	Blocks execution until all queued and pending tasks will be fully completed.

Result	waitForTask (Task &task)
	Blocks execution until all queued and pending tasks will be fully completed.

Detailed Description

Simple thread pool that executes tasks in a fixed number of worker threads.

This class is not copyable / moveable due to it containing Mutex and Condition variable. Additionally, this class does not allocate any memory by itself, and expects the caller to supply SC::ThreadPool::Task objects.

Warning: The caller is responsible of keeping Task address stable until the it will be completed. If it's not already completed the task must still be valid during ThreadPool::destroy or ThreadPool destructor.

Example:

    static const size_t wantedThreads = 4;
    static const size_t numTasks      = 100;
 
    // 1. Create the threadpool with the wanted number of threads
    SC::ThreadPool threadPool;
    SC_TEST_EXPECT(threadPool.create(wantedThreads));
 
    size_t values[numTasks];
 
    // 2. Allocate the wanted number of tasks. Tasks memory should be valid until a task is finished.
    SC::ThreadPool::Task tasks[numTasks];
 
    for (size_t idx = 0; idx < numTasks; idx++)
    {
        size_t* value = values + idx;
        *value        = idx;
 
        // 3. Setup the task function to execute on some random thread
        tasks[idx].function = [value]()
        {
            if (*value % 2)
            {
                SC::Thread::Sleep(10);
            }
            *value *= 100;
        };
        // 4. Queue the task in thread pool
        SC_TEST_EXPECT(threadPool.queueTask(tasks[idx]));
    }
 
    // 5. [Optional] Wait for a single task
    SC_TEST_EXPECT(threadPool.waitForTask(tasks[1]));
    SC_TEST_EXPECT(values[1] == 100);
 
    // 6. [Optional] Wait for all remaining tasks to be finished
    SC_TEST_EXPECT(threadPool.waitForAllTasks());
 
    // Checking Results
    bool allGood = true;
    for (size_t idx = 0; idx < numTasks; idx++)
    {
        allGood = allGood && (values[idx] == idx * 100);
    }
    SC_TEST_EXPECT(allGood);
 
    // 6. [Optional] Destroy the threadpool.
    // Note: destructor will wait for tasks to finish, but this avoids it from accessing invalid tasks,
    // as stack objects are reclaimed in inverse declaration order
    SC_TEST_EXPECT(threadPool.destroy());

Member Function Documentation

◆ create()

Result SC::ThreadPool::create ( size_t workerThreads )

Create a thread pool with the requested number of worker threads.

◆ destroy()

Result SC::ThreadPool::destroy ( )

Destroy the thread pool created previously with ThreadPool::create.

Warning: Tasks that are queued will NOT be executed (but you can use ThreadPool::waitForAllTasks for that)

◆ queueTask()

Result SC::ThreadPool::queueTask ( Task & task )

Queue a task (that should not be already in use)

◆ waitForAllTasks()

Result SC::ThreadPool::waitForAllTasks ( )

Blocks execution until all queued and pending tasks will be fully completed.

◆ waitForTask()

Result SC::ThreadPool::waitForTask ( Task & task )