Boost Thread Implementation of a Team of AD Threads
Keywords: boost thread implementation team ad threads bthread

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Boost Thread Implementation of a Team of AD Threads
See team_thread.hpp for this routines specifications. `

    # include <boost/thread.hpp>
    # include <cppad/cppad.hpp>
    # include "../team_thread.hpp"
    # define MAX_NUMBER_THREADS 48

    namespace {
    	using CppAD::thread_alloc;

    	// number of threads in the team
    	size_t num_threads_ = 1;

    	// no need to cleanup up thread specific data
    	void cleanup(size_t*)
    	{	return; }

    	// thread specific pointer the thread number (initialize as null)
    	boost::thread_specific_ptr<size_t> thread_num_ptr_(cleanup);

    	// type of the job currently being done by each thread
    	enum thread_job_t { init_enum, work_enum, join_enum } thread_job_;

    	// barrier used to wait for other threads to finish work
    	boost::barrier* wait_for_work_ = CPPAD_NULL;

    	// barrier used to wait for master thread to set next job
    	boost::barrier* wait_for_job_ = CPPAD_NULL;

    	// Are we in sequential mode; i.e., other threads are waiting for
    	// master thread to set up next job ?
    	bool sequential_execution_ = true;

    	// structure with information for one thread
    	typedef struct {
    		// The thread
    		boost::thread*       bthread;
    		// CppAD thread number as global (pointed to by thread_num_ptr_)
    		size_t               thread_num;
    		// true if no error for this thread, false otherwise.
    		bool                 ok;
    	} thread_one_t;

    	// vector with information for all threads
    	thread_one_t thread_all_[MAX_NUMBER_THREADS];

    	// pointer to function that does the work for one thread
    	void (* worker_)(void) = CPPAD_NULL;

    	// ---------------------------------------------------------------------
    	// in_parallel()
    	bool in_parallel(void)
    	{	return ! sequential_execution_; }

    	// ---------------------------------------------------------------------
    	// thread_number()
    	size_t thread_number(void)
    	{	// return thread_all_[thread_num].thread_num
    		return *thread_num_ptr_.get();
    	}
    	// --------------------------------------------------------------------
    	// function that gets called by boost thread constructor
    	void thread_work(size_t thread_num)
    	{	bool ok = wait_for_work_ != CPPAD_NULL;
    		ok     &= wait_for_job_  != CPPAD_NULL;
    		ok     &= thread_num     != 0;

    		// thread specific storage of thread number for this thread
    		thread_num_ptr_.reset(& thread_all_[thread_num].thread_num );

    		while( true )
    		{
    			// Use wait_for_jog_ to give master time in sequential mode
    			// (so it can change global information like thread_job_)
    			wait_for_job_->wait();

    			// case where we are terminating this thread (no more work)
    			if( thread_job_ == join_enum)
    				break;

    			// only other case once wait_for_job_ has been completed (so far)
    			ok &= thread_job_ == work_enum;
    			worker_();

    			// Use wait_for_work_ to inform master that our work is done and
    			// that this thread will not use global infromation until
    			// passing its barrier wait_for_job_ above.
    			wait_for_work_->wait();

    		}
    		thread_all_[thread_num].ok &= ok;
    		return;
    	}
    }

    bool team_create(size_t num_threads)
    {	bool ok = true;;

    	if( num_threads > MAX_NUMBER_THREADS )
    	{	std::cerr << "team_create: num_threads greater than ";
    		std::cerr << MAX_NUMBER_THREADS << std::endl;
    		exit(1);
    	}
    	// check that we currently do not have multiple threads running
    	ok  = num_threads_ == 1;
    	ok &= wait_for_work_ == CPPAD_NULL;
    	ok &= wait_for_job_  == CPPAD_NULL;
    	ok &= sequential_execution_;

    	size_t thread_num;
    	for(thread_num = 0; thread_num < num_threads; thread_num++)
    	{	// Each thread gets a pointer to its version of this thread_num
    		// so it knows which section of thread_all it is working with
    		thread_all_[thread_num].thread_num = thread_num;

    		// initialize
    		thread_all_[thread_num].ok = true;
    		thread_all_[0].bthread     = CPPAD_NULL;
    	}
    	// Finish setup of thread_all_ for this thread
    	thread_num_ptr_.reset(& thread_all_[0].thread_num);

    	// Now that thread_number() has necessary information for the case
    	// num_threads_ == 1, and while still in sequential mode,
    	// call setup for using CppAD::AD<double> in parallel mode.
    	thread_alloc::parallel_setup(num_threads, in_parallel, thread_number);
    	thread_alloc::hold_memory(true);
    	CppAD::parallel_ad<double>();

    	// now change num_threads_ to its final value.
    	num_threads_ = num_threads;

    	// initialize two barriers, one for work done, one for new job ready
    	wait_for_work_ = new boost::barrier(num_threads);
    	wait_for_job_  = new boost::barrier(num_threads);

    	// initial job for the threads
    	thread_job_           = init_enum;
    	if( num_threads > 1 )
    		sequential_execution_ = false;

    	// This master thread is already running, we need to create
    	// num_threads - 1 more threads
    	for(thread_num = 1; thread_num < num_threads; thread_num++)
    	{	// Create the thread with thread number equal to thread_num
    		thread_all_[thread_num].bthread =
    			new boost::thread(thread_work, thread_num);
    	}

    	// Current state is other threads are at wait_for_job_.
    	// This master thread (thread zero) has not completed wait_for_job_
    	sequential_execution_ = true;
    	return ok;
    }

    bool team_work(void worker(void))
    {
    	// Current state is other threads are at wait_for_job_.
    	// This master thread (thread zero) has not completed wait_for_job_
    	bool ok = sequential_execution_;
    	ok     &= thread_number() == 0;
    	ok     &= wait_for_work_  != CPPAD_NULL;
    	ok     &= wait_for_job_   != CPPAD_NULL;

    	// set global version of this work routine
    	worker_ = worker;

    	// set the new job that other threads are waiting for
    	thread_job_ = work_enum;

    	// Enter parallel exectuion when master thread calls wait_for_job_
    	if( num_threads_ > 1 )
    		sequential_execution_ = false;
    	wait_for_job_->wait();

    	// Now do the work in this thread and then wait
    	// until all threads have completed wait_for_work_
    	worker();
    	wait_for_work_->wait();

    	// Current state is other threads are at wait_for_job_.
    	// This master thread (thread zero) has not completed wait_for_job_
    	sequential_execution_ = true;

    	size_t thread_num;
    	for(thread_num = 0; thread_num < num_threads_; thread_num++)
    		ok &= thread_all_[thread_num].ok;
    	return ok;
    }

    bool team_destroy(void)
    {	// Current state is other threads are at wait_for_job_.
    	// This master thread (thread zero) has not completed wait_for_job_
    	bool ok = sequential_execution_;
    	ok     &= thread_number() == 0;
    	ok     &= wait_for_work_ != CPPAD_NULL;
    	ok     &= wait_for_job_  != CPPAD_NULL;

    	// set the new job that other threads are waiting for
    	thread_job_ = join_enum;

    	// enter parallel exectuion soon as master thread completes wait_for_job_
    	if( num_threads_ > 1 )
    			sequential_execution_ = false;
    	wait_for_job_->wait();

    	// now wait for the other threads to be destroyed
    	size_t thread_num;
    	ok &= thread_all_[0].bthread == CPPAD_NULL;
    	for(thread_num = 1; thread_num < num_threads_; thread_num++)
    	{	thread_all_[thread_num].bthread->join();
    		delete thread_all_[thread_num].bthread;
    		thread_all_[thread_num].bthread = CPPAD_NULL;
    	}
    	// now we are down to just the master thread (thread zero)
    	sequential_execution_ = true;

    	// destroy wait_for_work_
    	delete wait_for_work_;
    	wait_for_work_ = CPPAD_NULL;

    	// destroy wait_for_job_
    	delete wait_for_job_;
    	wait_for_job_ = CPPAD_NULL;

    	// check ok before changing num_threads_
    	for(thread_num = 0; thread_num < num_threads_; thread_num++)
    		ok &= thread_all_[thread_num].ok;

    	// now inform CppAD that there is only one thread
    	num_threads_ = 1;
    	thread_alloc::parallel_setup(num_threads_, CPPAD_NULL, CPPAD_NULL);
    	thread_alloc::hold_memory(false);
    	CppAD::parallel_ad<double>();

    	return ok;
    }

    const char* team_name(void)
    {	return "bthread"; }

`

Input File: multi_thread/bthread/team_bthread.cpp