dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Wed, Mar 30, 2011 at 10:22:36AM -0700, Johan Hake wrote:
> On Wednesday March 30 2011 10:15:01 Niclas Jansson wrote:
> > Johan Hake <johan.hake@xxxxxxxxx> writes:
> > > On Wednesday March 30 2011 10:02:28 Niclas Jansson wrote:
> > >> Johan Hake <johan.hake@xxxxxxxxx> writes:
> > >> > On Tuesday March 29 2011 23:27:27 Anders Logg wrote:
> > >> >> On Tue, Mar 29, 2011 at 11:10:17PM -0700, Johan Hake wrote:
> > >> >> > What triggers the error? Is it writing and/or reading to/from file.
> > >> >> > Is it assignment of data from within the read function in the
> > >> >> > test?
> > >> >> >
> > >> >> > johan
> > >> >>
> > >> >> It's the next line following the read:
> > >> >>   std::string filename(p1["filename"]);
> > >> >
> > >> > It took some time to find the parameter unit test ;)
> > >> >
> > >> >> So something goes wrong for at least one of the processes when the
> > >> >> parameters are read back from file. Here's what happens:
> > >> >>
> > >> >> 1. All processes create parameter set p0
> > >> >>
> > >> >> 2. Process 0 writes p0 to file
> > >> >>
> > >> >> 3. Everyone waits (barrier)
> > >> >>
> > >> >> 4. All processes read from the file into p1
> > >> >>
> > >> >> 5. All processes access parameters from p1 and compare to p0
> > >> >
> > >> > I guess it is 4 that goes wrong. I have tried to google varieties of
> > >> > "open shared file fstream". It looks like others have had the same
> > >> > problem.
> > >> >
> > >> > Johan
> > >>
> > >> I don't think it's enough with a barrier. It doesn't guarantee that
> > >> the data is flushed to the disk.
> > >
> > > But how could it work for some processes and not for others. Doesn't this
> > > indicate that the file is properly created?
> > >
> > > Johan
> >
> > True...
> >
> > But, say that the file is flushed some time after the barrier. Maybe
> > that is long enough for some of the processes to reach the "File f1"
> > statement before the file is flushed. The others arrives a bit later
> > and gets a valid file pointer.
>
> Ok, make sense.
>
> A flush at the end of each << call might not hurt anyway.

I tried a flush but it didn't help.

--
Anders


> Johan
>
> > Niclas
> >
> > >> An option is of course to use MPI I/O, but that would lead to a
> > >> painful rewrite of most I/O routines...
> > >>
> > >> Niclas
> > >>
> > >> >
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