[vtk-developers] suggestion for vtkMultiThreader.cxx

[Simon Warfield]

vtkMultiThreader.cxx in some places uses a strategy of starting 
this->NumberOfThreads-1 additional threads to run work in separate threads
and runs a pthread_join to wait for these jobs to complete.

  The thread running the pthread_join is suspended until the thread it is
waiting for finishes.  If there are this->NumberOfThreads CPUs available
for work then running only this->NumberOfThreads-1 jobs wastes wallclock time.
  It would be better to run this->NumberOfThreads of jobs.


vtkMultiThreader.cxx lines 322-341:
  // Using POSIX threads
  //
  // We want to use pthread_create to start this->NumberOfThreads-1 additional
  // threads which will be used to call this->SingleMethod(). The
  // parent thread will also call this routine.  When it is done,
  // it will wait for all the children to finish.
  //
  // First, start up the this->NumberOfThreads-1 processes.  Keep track
  // of their process ids for use later in the pthread_join call

--
Simon Warfield, Ph.D. warfield at bwh.harvard.edu Phone:617-732-7090
http://www.spl.harvard.edu/~warfield           FAX:  617-582-6033
Thorn 329, Brigham and Women's Hospital, Harvard Medical School
Department of Radiology, 75 Francis St, Boston, MA, 02115