Victor Eijkhout <[email protected]> writes: > On , 2020Jan22, at 09:11, Felix Huber > <[email protected]<mailto:[email protected]>> wrote: > > weak scaling behaviour in a CG solver > > Norms and inner products have Log(P) complexity, so you’ll never get perfect > weak scaling.
Allreduce is nearly constant time with hardware collectives on nice networks. The increased cost frequently observed is due to load imbalance causing different processes to enter at different times. https://www.mcs.anl.gov/~fischer/gop/
