Ok, thanks. Then one has to be careful in HPC when using the term so each time it is used everyone in the conversation knows which one it is referring to.
> On Sep 22, 2019, at 8:33 AM, Jed Brown <j...@jedbrown.org> wrote: > > "Smith, Barry F." <bsm...@mcs.anl.gov> writes: > >>> On Sep 21, 2019, at 11:43 PM, Jed Brown <j...@jedbrown.org> wrote: >>> >>> "Smith, Barry F." <bsm...@mcs.anl.gov> writes: >>> >>>> Jed, >>>> >>>> What does latency as a function of message size mean? It is in the plots >>> >>> It's just the wall-clock time to ping-pong a message of that size. All >>> the small sizes take the same amount of time (i.e., the latency), then >>> transition to being network bandwidth limited for large sizes. >> >> Thanks, this is fine for the small size. But he has the graph up to >> size 1000000 and the plotted values change for larger sizes, surely >> for 1000000 the time is a combination of latency and bandwidth? >> Isn't calling it latency a misnomer, or do people use this >> inconsistent terminology when doing ping-pongs? > > Latency of an operation is just how long from when you initiate it until > it completes. Latency in a performance model, such as LogP, is additive > with other factors (like bandwidth and compute throughput).
