[mvapich-discuss] mvapich 0.9.7

[Sayantan Sur]

Hi Roland,

Thanks for your posting this question on this list.

>a quick question:
>
>Does it have a big impact on performance and/or functionality whether I
>choose PCIe / PCI-X or SDR/DDR when compiling?
>  
>
The choice of PCIe/PCI-X has the effect of choosing different internal 
MPI buffer sizes. With PCIe, we have faster communication, so buffer 
sizes are a little smaller than with PCI-X. The choice of SDR/DDR 
affects the choice of the optimal MTU value (required for qp 
configuration), this value is important for MPI micro-benchmarks over 
PCIe achieving the peak bandwidth. That said, the impact of these 
choices on end applications may be difficult to notice, depending upon 
the application characteristics and other system parameters.

Neither of these choices should affect the functionality aspect of MVAPICH.

>I'm wondering what to do in a cluster where I have mixed hosts with
>PCIe / PCI-X adapters for instance.
>  
>
Our suggestion would be that you use PCI-X settings. This is because the 
PCIe InfiniBand cards support some features (utilized by MVAPICH) which 
are not yet available for PCI-X cards.

Hope this helps.

Thanks,
Sayantan.

-- 
http://www.cse.ohio-state.edu/~surs