OpenSpace/modules/globebrowsing/other/concurrentjobmanager.h

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 * OpenSpace                                                                             *
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 * Copyright (c) 2014-2016                                                               *
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#ifndef __CONCURRENT_JOB_MANAGER_H__
#define __CONCURRENT_JOB_MANAGER_H__

#include <glm/glm.hpp>
#include <memory>
#include <ostream>
#include <thread>
#include <queue>
#include <atomic>

#include <modules/globebrowsing/other/concurrentqueue.h>

#include <ghoul/misc/assert.h>



namespace openspace {


    // Templated abstract base class representing a job to be done.
    // Client code derive from this class and implement the virtual execute() method
    template<typename P>
    struct Job {

        Job() { }
        virtual ~Job() { }

        virtual void execute() = 0;
        virtual std::shared_ptr<P> product() = 0;
    
    };




    /* 
     * Templated Concurrent Job Manager
     * This class is used execute specific jobs on one (1) parallell thread
     */
    template<typename P>
    class ConcurrentJobManager{
    public:
        ConcurrentJobManager()
        : _hasWorkingThread(false)
        {

        }

        ~ConcurrentJobManager() {

        }


        void enqueueJob(std::shared_ptr<Job<P>> job) {
            _incomingJobs.push(job);
            if (!_hasWorkingThread) {
                _hasWorkingThread = true; // Can only be set to true by the main thread
                executeJobsInSeparateThread();
            }
        }

        void clearEnqueuedJobs() {
            while (_incomingJobs.size()) {
                _incomingJobs.pop();
            }
        }

        std::shared_ptr<Job<P>> popFinishedJob() {
            ghoul_assert(_finishedJobs.size() > 0, "There is no finished job to pop!");
            return _finishedJobs.pop();
        }

        size_t numFinishedJobs() {
            return _finishedJobs.size();
        }


    
    private:


        void executeJobsInSeparateThread() {
            // Create new thread and run workerThreadMainTask on that thread
            std::thread t(&ConcurrentJobManager::workerThreadMainTask, this);
            t.detach();
        }
        
        void workerThreadMainTask() {
            while (_incomingJobs.size() > 0) {
                auto job = _incomingJobs.pop();                

                job->execute();

                _finishedJobs.push(job);
            }

            _hasWorkingThread = false; // Can only be set to false by worker thread
        }

        ConcurrentQueue<std::shared_ptr<Job<P>>> _incomingJobs;
        ConcurrentQueue<std::shared_ptr<Job<P>>> _finishedJobs;

        // Using this atomic bool is probably not optimal - Should probably
        // use a conditional variable instead
        std::atomic<bool> _hasWorkingThread;
        std::atomic<int> _numActiveThreads;

    };


} // namespace openspace



#endif // __CONCURRENT_JOB_MANAGER_H__