[petsc-dev] synchronized printing, singletons, and jumbled GAMG/BJacobi output

[Jed Brown]

Barry Smith <bsmith at mcs.anl.gov> writes:

>>  Instead, it
>> uses block Jacobi in which all blocks but one are empty.
>
>    This seems a rather ad hoc way of handling it. Why not have a
>    proper mechanism for telescoping solvers rather than an ad hoc
>    block Jacobi with 0 sizes on most blocks?

How would that "proper mechanism" look?

>>>  And why does it have different solvers on each process? 
>> 
>> It doesn't, but it calls PCBJacobiGetSubKSP() so as to configure the
>> inner PC to be PCLU, but PCBJacobiGetSubKSP conservatively sets this
>> flag:
>> 
>>  jac->same_local_solves = PETSC_FALSE;        /* Assume that local solves are now different;
>>                                                  not necessarily true though!  This flag is
>>                                                  used only for PCView_BJacobi() */
>
>    Why not just fix this instead. Fix it so it doesn't set the flag in this situation.

Sure, where would we set that flag?  Or, how do we compare solvers (on
different subcomms) for "equivalent" configuration?