[Gretl-devel] Re: MPI issue

On 13.08.2019 21:28, Allin Cottrell wrote: > 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> Ok, thanks Allin. In my case "# write bundle HERE" is done before MPI block, but I understand it doesn't matter?