[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>
Allin