[petsc-users] AOCreateBasic is not scaling

[M. Scot Breitenfeld]

Hi,

First, thanks for the suggestion on using MPISBAIJ for my A matrix, it
seems to have cut down on my memory and assembly time. For a 1.5 million
dof problem:
     
    # procs:                  2        4        8           16
----------------------------------------------------------------
Assembly (sec):        245     124      63       86
Solver (sec):              924     578     326     680

Memory (GB):          2.5        1.4     .877    .565

The problem I have is the amount of time it's taking in AOCreateBasic,
it takes longer then assembling,

    # procs:                            2        4        8         16
---------------------------------------------------------------------
AOCreateBasic (sec):         .6      347      170     197

Is there something that I can change or something I can look for that
might be causing this increase in time as I go from 2 to 4 processors
(at least it scales from 4 to 8 processors). I read in the archive that
AOCreateBasic is not meant to be scalable so maybe there is nothing I
can do.

Thanks,
Scot