Hacker News Reader

HNHacker News

Top New Best Ask Show Jobs

Comment by wffurr | Hacker News Reader

Parent Full thread

wffurr·

Did you RTFA? It's about MPI:

"MPI is a language-independent communications protocol used to program parallel computers."

Runs fine on commodity clusters.

View on HN

>Runs fine on commodity clusters.

Kind of.... For simple, low communication jobs this is true. But when you start trying to find the eigenvectors of a large sparse matrix, communication becomes your bottleneck, at which point MPI on commodity clusters (those without a really fancy interconnect) "works", but not fast enough to be useful.

I don't think "really fancy interconnects" makes a cluster not commodity, since the original post in this thread is about supercomputer processors. You can put Infiniband in any system with a PCI-e 3.0 bus.

Communication would become a bottleneck regardless of whether you're using MPI or something else. The problem you're talking about has nothing to do with MPI; it is intrinsic to distributed computing itself.

And what system on commodity clusters is fast enough in this case?

What would you define as a "commodity cluster"? To me it's a 512-core vendor-specific blade server with special interfaces to get more bandwith at lower latency across longer links. But maybe i'm just an old fogey.

1) Not vendor specific 2) Not blades 3) 10Gbe, not special interfaces

That is a commodity cluster.

blades were never more than a marketing trick: the offer nothing that can't be achieved in a standard chassis. there were a few multi-chassis SMP/NUMA machines that had cache coherency over external interfaces, but that was neither commodity nor HPC.

Did you fucking read TFA?

It's title literally is: "HPC is dying, and MPI is killing it".

His comment shows more understanding of the article's main point (about the demise of HPC) that your "it's about MPI"...

Reply on news.ycombinator.com