[Gretl-devel] Re: MPI issue

On Tue, 13 Aug 2019, Marcin Błażejowski wrote: > On 13.08.2019 19:22, Allin Cottrell wrote: >> On Tue, 13 Aug 2019, Marcin Błażejowski wrote: >> >>> It looks like the problem with concurent access to the file. I solved >>> the issue, but the solution is quite numb: >>> ########################## >>> loop i=0..$mpisize-1 --quiet >>>     if ($mpirank == i) >>>         MODEL = bread("MODEL") >>>     else >>>         sleep(1) >>>     endif >>> endloop >>> ########################## >> >> Possibly relevant questions: Is the bundle file gzipped or just plain >> XML? How/when is the bundle file created? > > Allin, > > this is a plain XML created by bwrite() few lines before bread() is > used: OK. I assume the bundle is being written by one process, to be read by all, or all the others? If so, you probably need to add an MPI barrier, otherwise some processes may try to start reading the file before the writer has finished writing it. We don't have a simple MPI barrier as such in our hansl implementation of MPI (maybe we should have such), but you could just broadcast a scalar from the process that's writing the file. Something like: <hansl> # write bundle HERE scalar bundle_ready if $mpirank == 0 # or whoever is writing     bundle_ready = 1 endif mpibcast(&bundle_ready) if bundle_ready     # read bundle HERE endif <hansl>