[petsc-dev] always calling MPI_Init_thread?

[Jed Brown]

On Thu, Feb 14, 2013 at 1:16 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
>
>    Do we really ALWAYS want to call this version even if we are not
> monkeying with threads at ALL?
>
>     Thanks
>
>    Barry
>
>  ierr = MPI_Initialized(&flag);CHKERRQ(ierr);
>   if (!flag) {
>     if (PETSC_COMM_WORLD != MPI_COMM_NULL)
> SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"You cannot set PETSC_COMM_WORLD if
> you have not initialized MPI first");
> #if defined(PETSC_HAVE_MPI_INIT_THREAD)
>     {
>       PetscMPIInt provided;
>       ierr =
> MPI_Init_thread(argc,args,MPI_THREAD_FUNNELED,&provided);CHKERRQ(ierr);
>     }
> #else
>     ierr = MPI_Init(argc,args);CHKERRQ(ierr);
>

The implementation of MPI_Init just probes around the environment and calls
MPI_Init_thread. There is no performance advantage of MPI_THREAD_SINGLE
over MPI_THREAD_FUNNELED so I think the code here is fine.
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