#1333 ISTL GMRES parallel performance bug
|Reported by||Tobias Malkmus (firstname.lastname@example.org)|
|Reported at||Aug 20, 2013 19:31|
|Operating System||Unspecified / All|
In parallel, the ISTL GMRES implementation calls in each iteration step_sp.dot( ... ) for each Krylov-basisvector, which is at most "number of Restarts"-times.
Usually, a global summation over each process is called in each _sp.dot( ... ) evaluation.
This makes at most "number of Restarts" + 3 numbers of global communication per iteration. In my personal code the parallel performance breaks down for more than 2 processes.
At the moment i don't have an example for the performance break down. I will try to provide one tomorrow.