On Tue, Feb 12, 2013 at 7:09 PM, Karl Rupp <rupp@mcs.anl.gov> wrote:

Which crossover are you referring to? The CPU versus GTX285 at about 20k
dofs, but with only very small gains for another order of magnitude?

I assume it's the cross-over of Xeon Phi vs. Xeon,

MIC is slower than Xeon by more than an order of magnitude at 10k dofs.

but almost all cross-overs happen in the 10k-100k region and are due to PCI-Express latency.

Why is PCI-Express latency important here? Can't the MIC code run entirely on the device?

Scaling this to large clusters, replace Xeon Phi by compute node, PCI-Express by GB-Ethernet/Infiniband as well as change the timescale a bit and you're probably not too far off...