G4MTBarrier.cc

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// $Id$
//
// ---------------------------------------------------------------
/*
 * G4MTBarrier.cc
 *
 *  Created on: Feb 10, 2016
 *      Author: adotti
 */

#include "G4MTBarrier.hh"
#include "G4AutoLock.hh"

G4MTBarrier::G4MTBarrier(unsigned int numThreads ) :
  m_numActiveThreads(numThreads),
  m_counter(0),
  m_mutex(G4MUTEX_INITIALIZER),
  m_counterChanged(G4CONDITION_INITIALIZER),
  m_continue(G4CONDITION_INITIALIZER)
{
#if defined(WIN32)
  InitializeCriticalSection( &cs1 );
  InitializeCriticalSection( &cs2 );
#endif
}

void G4MTBarrier::ThisWorkerReady() {
  //Step-1: Worker acquires lock on shared resource (the counter)
#ifndef WIN32
  G4AutoLock lock(&m_mutex);
#else
  EnterCriticalSection( &cs1 );
#endif
  //Step-2: Worker increases counter
  ++m_counter;
  //Step-3: Worker broadcasts that the counter has changed
  G4CONDITIONBROADCAST(&m_counterChanged);
  //Step-4: Worker waits on condition to continue
#ifndef WIN32
  G4CONDITIONWAIT(&m_continue,&m_mutex);
#else
# ifdef G4MULTITHREADED
  G4CONDITIONWAIT(&m_continue,&cs1);
# endif
  LeaveCriticalSection(&cs1);
#endif
}

void G4MTBarrier::Wait() {
  while (true)
  {
      //Step-2: Acquires lock on shared resource (the counter)
#ifndef WIN32
      G4AutoLock lock(&m_mutex);
#else
      EnterCriticalSection(&cs2);
#endif
      //If the counter equals active threads, all threads are ready, exit the loop
      if ( m_counter == m_numActiveThreads ) { break; }
      //Step-3: Not all workers are ready, wait for the number to change
      //before repeating the check
#ifdef WIN32
#     ifdef G4MULTITHREADED
      G4CONDITIONWAIT(&m_counterChanged,&cs2);
#     endif
      LeaveCriticalSection(&cs2);
#else
      G4CONDITIONWAIT(&m_counterChanged,&m_mutex);
#endif
  }
}

void G4MTBarrier::ReleaseBarrier() {
  //Step-4: re-aquire lock and re-set shared resource for future re-use
  G4AutoLock lock(&m_mutex);
  m_counter = 0;
  G4CONDITIONBROADCAST(&m_continue);
}

void G4MTBarrier::WaitForReadyWorkers() {
  //Step-1: Master enters a loop to wait all workers to be ready
  Wait();
  //Done, all workers are ready, broadcast a continue signal
  ReleaseBarrier();
}

void G4MTBarrier::ResetCounter() {
  G4AutoLock l(&m_mutex);
  m_counter = 0;
}

unsigned int G4MTBarrier::GetCounter() {
  G4AutoLock l(&m_mutex);
  const unsigned int result = m_counter;
  return result;
}