Documentation

This class can be used to implement a barrier. In many applications, and especially numerical applications, while part of the algorithm can be parallelized, other parts are inherently sequential, as shown in the following:

    Thread1                             Thread2 through Threadn
  
    while(many_iterations) {            while(many_iterations) {

      sequential_computation
      --- Barrier ---                     --- Barrier ---
      parallel_computation                parallel_computation
    }                                   }
    

The nature of the parallel algorithms for such a computation is that little synchronization is required during the computation, but synchronization of all the threads employed is required to ensure that the sequential computation is finished before the parallel computation begins.

The barrier forces all the threads that are doing the parallel computation to wait until all threads involved have reached the barrier. When they've reached the barrier, they are released and begin computing together.

 
    Example: