[mpich-discuss] broadcast and reduce mechanism

[Dave Goodell]

You can find some information in this paper: http://www.mcs.anl.gov/~thakur/papers/mpi-coll.pdf

However since that was written there have been a few changes, some  
major and some minor.  One difference is that we now perform those  
collective operations hierarchically on SMP systems (intranode,  
internode, then intranode again).  Also, additional algorithms might  
have been selected and the cutoff points are almost certainly  
different.  So the best way to figure out what's going on in there is  
to read the code.

As far as I know we don't use sequential communication to implement  
any of our collective operations.

-Dave

On Aug 11, 2009, at 9:34 PM, Gra zeus wrote:

> Hello,
>
> Can any one comfirm or link me to documents that explain  
> communication mechanism of MPI_Bcast and MPI_Reduce?
>
> I searched in google and It said Bcast,Reduce can use tree algorithm  
> or sequential communication.
> However, I can't find any specification that indicate communication  
> mechanism of MPI_Bcast and MPI_Reduce in MPICH2.
>
> thx,
> gra
>