Chris: when jit is called on a subset of processors, the others obviously cannot participate. The check for rank 0 within the group is exactly to stop all the other participating processors from writing to disk simultaneously. So if the instant cache is in a shared directory, there's no more disk usage here.
Of course if you have two groups doing exactly the same operations, then rank 0 from each group will race for copying into the instant cache. In that case we don't have mpi communication between the racing processors because they are on different groups, and we'll need the file locking in instant to work. Which I guess is still a problem with NFS... Martin 26. nov. 2014 09:57 skrev "Johan Hake" <[email protected]>: > > > On Wed, Nov 26, 2014 at 9:55 AM, Chris Richardson <[email protected]> > wrote: > >> On 25/11/2014 21:48, Johan Hake wrote: >> >>> Hello! >>> >>> I just pushed some fixes to the jit interface of DOLFIN. Now one can >>> jit on different mpi groups. Previously jiting was only done on rank 1 >>> of the mpi_comm_world. Now it is done on rank 1 of any passed group >>> communicator. >>> >> >> Maybe I'm missing something here, but could you explain what is the >> advantage of doing it this way? >> If you have several processes JITing the same code, where do they save it >> in the filesystem? >> If they all share the same filesystem, surely this will take up more >> resources, as more processes >> try to write at the same time? >> > > That is just an unintended (necessary?) side effect. > > Or is it intended for cases where the Expression is different on different >> MPI groups? > > > Yes. > > Johan > > > >> >> >> Chris >> > > > _______________________________________________ > fenics mailing list > [email protected] > http://fenicsproject.org/mailman/listinfo/fenics > >
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