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namespace Gecode { namespace Support {
/// Baseclass for jobs with return type \a RetType template<class RetType> class Job { public: /// Run a job with iterator index \a i virtual RetType run(int i) = 0; /// Destructor virtual ~Job(void) {} };
/// Class to throw an exception to stop new jobs from being started template<class RetType> class JobStop { protected: /// The result stored RetType r; public: /// Constructor JobStop(RetType r0); /// Return the passed result RetType result(void) const; };
template<class Jobs, class RetType> /** * \brief Parallel iterator that runs jobs with a given number of threads * * It takes an iterator over jobs as input and acts as an iterator * over the jobs' results. The order of iteration is not kept. The * iterator runs several jobs as defined by the input iterator in * parallel using a maximal number of threads. * * The iterator can be stopped creating new jobs if one of the running * jobs throws an exception of type \a JobStop. In that case the result * of the stopped job is defined by the default constructor of the * return type \a RetType. Already running jobs are not stopped and * deliver their results as usual. * */ class RunJobs { protected: class Master; /// The actual worker using a thread to run a job class Worker : public Runnable { protected: /// The job to run Job<RetType>* job; /// The master to communicate with Master* master; /// Original iterator index of job int idx; public: /// Initialize worker Worker(Job<RetType>* j, Master* m, int i); /// Run jobs virtual void run(void); /// Nothing to delete (done in run) virtual ~Worker(void); }; class Master { protected: /// Mutex for synchronizing access Mutex m; /// Event is triggered if a the first job is added to queue Event e; /// Number of threads currently not in use unsigned int n_threads; /// Input jobs Jobs& jobs; /// Index of next job to be created int idx; /// Result from a the first stopped job (passed in exception) RetType sres; /// Index of the first stop that has been stopped (-1 if none) int sidx; /// Queue of not yet requested results DynamicQueue<RetType,Heap> rs; public: /// Get next job witth index \a i, if possible Job<RetType>* next(int& i); /// Report result \a r by a worker void report(RetType r); /// Report that a job with index \a i has been stopped void stop(RetType r, int i); /// Test whether all jobs are done bool done(void) const; /// Initialize with job iterator \a j and maximal number of threads \a m Master(Jobs& j, unsigned int m); /// Run next job and return true if succesful and assign \a r to its result bool run(RetType& r); /// Whether a job has thrown a \a JobStop exception bool stopped(void) const; /// Return index of first job that has thrown a \a JobStop exception (-1 if none) with its result int stoppedjob(RetType& r) const; /// Whether a new thread is needed for deletion bool needthread(void); /// Destructor ~Master(void); }; /// A class to delete the master (running in parallel) class Deleter : public Runnable { protected: /// The master to be deleted Master* master; public: /// Initialize with master \a m Deleter(Master* m); /// Perform deletion virtual void run(void); }; /// The actual master Master* master; public: /// Initialize with job iterator \a j and maximal number of threads \a m RunJobs(Jobs& j, unsigned int m); /// Run next job and return true if succesful and assign \a r to its result bool run(RetType& r); /// Whether a job has thrown a \a JobStop exception with index \a i and result \a r bool stopped(int& i, RetType& r) const; /// Destructor ~RunJobs(void); };
template<class RetType> forceinline JobStop<RetType>::JobStop(RetType r0) : r(r0) {}
template<class RetType> forceinline RetType JobStop<RetType>::result(void) const { return r; }
template<class Jobs, class RetType> forceinline RunJobs<Jobs,RetType>::Worker::Worker(Job<RetType>* j, Master* m, int i) : Runnable(true), job(j), master(m), idx(i) {} template<class Jobs, class RetType> RunJobs<Jobs,RetType>::Worker::~Worker(void) {}
template<class Jobs, class RetType> inline int RunJobs<Jobs,RetType>::Master::stoppedjob(RetType& r) const { r = sres; return sidx; }
template<class Jobs, class RetType> inline bool RunJobs<Jobs,RetType>::Master::stopped(void) const { return sidx >= 0; }
template<class Jobs, class RetType> forceinline Job<RetType>* RunJobs<Jobs,RetType>::Master::next(int& i) { m.acquire(); Job<RetType>* j; if (jobs() && !stopped()) { j = jobs.job(); i=idx++; } else { j = nullptr; n_threads--; e.signal(); } m.release(); return j; }
template<class Jobs, class RetType> forceinline void RunJobs<Jobs,RetType>::Master::report(RetType r) { m.acquire(); rs.push(r); e.signal(); m.release(); }
template<class Jobs, class RetType> forceinline void RunJobs<Jobs,RetType>::Master::stop(RetType r, int i) { m.acquire(); if (!stopped()) { sres=r; sidx = i; } rs.push(r); e.signal(); m.release(); }
template<class Jobs, class RetType> void RunJobs<Jobs,RetType>::Worker::run(void) { do { try { RetType r = job->run(idx); master->report(r); } catch (JobStop<RetType>& js) { master->stop(js.result(),idx); } delete job; job = master->next(idx); } while (job != nullptr); }
template<class Jobs, class RetType> forceinline bool RunJobs<Jobs,RetType>::Master::done(void) const { return (n_threads == 0) && (!jobs() || stopped()) && rs.empty(); }
template<class Jobs, class RetType> inline RunJobs<Jobs,RetType>::Master::Master(Jobs& j, unsigned int m_threads) : n_threads(0), jobs(j), idx(0), sidx(-1), rs(heap) { m.acquire(); while ((n_threads < m_threads) && jobs()) { if (stopped()) break; Thread::run(new Worker(jobs.job(),this,idx)); n_threads++; idx++; } m.release(); }
template<class Jobs, class RetType> inline bool RunJobs<Jobs,RetType>::Master::run(RetType& r) { m.acquire(); if (done()) { m.release(); return false; } if (!rs.empty()) { r = rs.pop(); m.release(); return true; } m.release(); while (true) { e.wait(); m.acquire(); if (done()) { m.release(); return false; } if (!rs.empty()) { r = rs.pop(); m.release(); return true; } m.release(); } GECODE_NEVER; }
template<class Jobs, class RetType> inline bool RunJobs<Jobs,RetType>::Master::needthread(void) { bool n; m.acquire(); while (!rs.empty()) rs.pop().~RetType(); sidx = 0; n = !done(); m.release(); return n; }
template<class Jobs, class RetType> inline RunJobs<Jobs,RetType>::Master::~Master(void) { sidx = 0; RetType r; while (run(r)) r.~RetType(); }
template<class Jobs, class RetType> forceinline RunJobs<Jobs,RetType>::Deleter::Deleter(Master* m) : Runnable(true), master(m) {}
template<class Jobs, class RetType> void RunJobs<Jobs,RetType>::Deleter::run(void) { delete master; }
template<class Jobs, class RetType> inline bool RunJobs<Jobs,RetType>::stopped(int& i, RetType& r) const { i = master->stoppedjob(r); return i >= 0; }
template<class Jobs, class RetType> inline RunJobs<Jobs,RetType>::RunJobs(Jobs& j, unsigned int m) : master(new Master(j,m)) {}
template<class Jobs, class RetType> inline bool RunJobs<Jobs,RetType>::run(RetType& r) { return master->run(r); }
template<class Jobs, class RetType> inline RunJobs<Jobs,RetType>::~RunJobs(void) { if (!master->needthread()) delete master; else Thread::run(new Deleter(master)); }
}}
// STATISTICS: support-any