Mm,I don't understand. The experiments on my appliciation shows that an intensive use of Barrier+ Reduce is more faster than a single Reduce.
2010/9/9 Ralph Castain <r...@open-mpi.org> > As people have said, these time values are to be expected. All they reflect > is the time difference spent in reduce waiting for the slowest process to > catch up to everyone else. The barrier removes that factor by forcing all > processes to start from the same place. > > No mystery here - just a reflection of the fact that your processes arrive > at the MPI_Reduce calls at different times. > > > On Sep 9, 2010, at 1:14 AM, Gabriele Fatigati wrote: > > More in depth, > > total execution time without Barrier is about 10000 sec. > > Total execution time with Barrier+Reduce is 9453, with 128 procs. > > 2010/9/9 Terry Frankcombe <te...@chem.gu.se> > >> Gabriele, >> >> Can you clarify... those timings are what is reported for the reduction >> call specifically, not the total execution time? >> >> If so, then the difference is, to a first approximation, the time you >> spend sitting idly by doing absolutely nothing waiting at the barrier. >> >> Ciao >> Terry >> >> >> -- >> Dr. Terry Frankcombe >> Research School of Chemistry, Australian National University >> Ph: (+61) 0417 163 509 Skype: terry.frankcombe >> >> _______________________________________________ >> users mailing list >> us...@open-mpi.org >> http://www.open-mpi.org/mailman/listinfo.cgi/users >> >> > > > -- > Ing. Gabriele Fatigati > > Parallel programmer > > CINECA Systems & Tecnologies Department > > Supercomputing Group > > Via Magnanelli 6/3, Casalecchio di Reno (BO) Italy > > www.cineca.it Tel: +39 051 6171722 > > g.fatigati [AT] cineca.it > _______________________________________________ > users mailing list > us...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/users > > > > _______________________________________________ > users mailing list > us...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/users > -- Ing. Gabriele Fatigati Parallel programmer CINECA Systems & Tecnologies Department Supercomputing Group Via Magnanelli 6/3, Casalecchio di Reno (BO) Italy www.cineca.it Tel: +39 051 6171722 g.fatigati [AT] cineca.it
