dolfin team mailing list archive

[Johan Hake <johan.hake@xxxxxxxxx>]

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

> 
> --
> Anders
> 
> > On Tuesday March 29 2011 22:53:01 Anders Logg wrote:
> > > The parameter unit test is sometimes failing in parallel. On my local
> > > machine it always seems to work with 2 or 3 processes, but sometimes
> > > it fails with 4, giving the same error message as the buildbot:
> > > 
> > > ##Failure Location unknown## : Error
> > > Test name: InputOutput::test_simple
> > > uncaught exception of type St13runtime_error
> > > - *** Error: Unable to access parameter "filename" in parameter set
> > > "test", par
> > > ameter not defined.
> > > 
> > > Failures !!!
> > > Run: 2   Failure total: 1   Failures: 0   Errors: 1
> > > 
> > > There is a check for which process writes to file and a barrier that
> > > should make sure everyone waits until the file gets written.
> > > 
> > >   // Save to file
> > >   if (dolfin::MPI::process_number() == 0)
> > >   {
> > >   
> > >     File f0("test_parameters.xml");
> > >     f0 << p0;
> > >   
> > >   }
> > >   dolfin::MPI::barrier();
> > >   
> > >   // Read from file
> > >   Parameters p1;
> > >   File f1("test_parameters.xml");
> > >   f1 >> p1;
> > > 
> > > I thought that should do the trick, but apparently not.
> > > 
> > > Any ideas what goes wrong?