Thanks for the clarification. I also observed that the number of KSP iterations increases with an increase in the levels of AMG. Is this true, in general, for all/most applications?
-Manav > On Oct 29, 2018, at 12:53 PM, Jed Brown <[email protected]> wrote: > > Manav Bhatia <[email protected]> writes: > >> Thanks, Jed. >> >> The description says: “ Square the graph, ie. compute A'*A before >> aggregating it" >> >> What is A here? > > The original matrix, or its "graph" (your 6x6 blocks condensed to scalars). > >> What is the impact of setting this to 0, which led to a very significant >> increase in the CPU time in my case? > > The aggregates are formed on the connectivity of your original matrix, > so root nodes are aggregated only with their first neighbors, resulting > in slower coarsening.
