[MPICH2-dev] Broadcast on non-power of two nodes

[Brightwell, Ronald]

>     The cutoff points were set on some Myrinet cluster. You will need to
> experiment and use appropriate ones for Red Storm.

Ok.

> 
> The ring algorithm for allgather takes nprocs-1 steps. In each step, each
> process sends to rank+1 and receives from rank-1. So, a lot of the
> communication should happen concurrently, unless it is getting serialized by
> the network for some reason. Can that happen on your network?

No, it shouldn't.

> 
> Also, you may want to consider adding an extra condition (nprocs) in if
> statement that selects the allgather algorithm. For nprocs beyond some value
> you may want to use recursive doubling even for non powers of two.
> 

Ok.  We'll look into that.

Thanks :)

-Ron