[petsc-users] A bad commit affects MOOSE

[Smith, Barry F.]

   My mistake, xSDK only says you need to use the given communicators; it doesn't say you need to use a duped version.

    M3. Each xSDK-compatible package that utilizes MPI must restrict its MPI operations to MPI communicators that are provided to it and not use directly MPI_COMM_WORLD. The package should use configure tests or version tests to detect MPI 2 or MPI 3 features that may not be available; it should not be assumed that a full MPI 2 or MPI 3 implementation is available. The package can change the MPI error-handling mode by default but should have an option to prevent it from changing the MPI error handling (which may have been set by another package or the application). The package should also behave appropriately regardless of the MPI error handling being used. There is no requirement that the package provide a sequential (non-MPI) version, although this functionality is welcome, too. If the package provides a sequential version, there is no requirement that it be compatible or usable with other xSDK-compliant packages running without MPI.

  Barry


    
> On Apr 3, 2018, at 4:22 PM, Matthew Knepley <knepley at gmail.com> wrote:
> 
> On Tue, Apr 3, 2018 at 6:20 PM, Jed Brown <jed at jedbrown.org> wrote:
> Derek Gaston <friedmud at gmail.com> writes:
> 
> > On Tue, Apr 3, 2018 at 4:06 PM Jed Brown <jed at jedbrown.org> wrote:
> >
> >> Communicators should be cheap.  One per library per "size" isn't a huge
> >> number of communicators.
> >>
> >
> > I agree - but that's not what we're getting here.  We're getting one per
> > "object" (Mat / Preconditioner, etc.) associated with the library per
> > "size".  If we can fix that I agree that there's no problem (we use a lot
> > of libraries... but not 2000 separate ones simultaneously!).
> 
> So PETSc needs to dup and attach a hypre communicator because they
> aren't interested in doing it themselves.  Not hard to implement, just
> mildly annoying.
> 
> Can't someone tell them its an xSDK requirement?
> 
>    Matt
> 
> -- 
> What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
> -- Norbert Wiener
> 
> https://www.cse.buffalo.edu/~knepley/