[mpich-discuss] broadcast and reduce mechanism

[Rajeev Thakur]

The code is in the src/mpi/coll directory. See bcast.c and reduce.c.

Rajeev 

> -----Original Message-----
> From: mpich-discuss-bounces at mcs.anl.gov 
> [mailto:mpich-discuss-bounces at mcs.anl.gov] On Behalf Of Dave Goodell
> Sent: Wednesday, August 12, 2009 9:01 AM
> To: mpich-discuss at mcs.anl.gov
> Subject: Re: [mpich-discuss] broadcast and reduce mechanism
> 
> 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
> >
> 
>