dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Sun, Mar 14, 2010 at 07:39:45AM +0000, Garth N. Wells wrote:
>
>
> Anders Logg wrote:
> > On Fri, Mar 12, 2010 at 06:58:22PM -0000, noreply@xxxxxxxxxxxxx wrote:
> >> ------------------------------------------------------------
> >> revno: 4635
> >> committer: Garth N. Wells <gnw20@xxxxxxxxx>
> >> branch nick: dolfin-all
> >> timestamp: Fri 2010-03-12 18:53:05 +0000
> >> message:
> >>   Work on reading Vectors in parallel. Some issues to resolve still.
> >>
> >>   Some issues:
> >>   - How should files be named when in parallel?
> >>   - Should we have a 'master' xml file which points to the files
> >>   - from different processes?
> >
> > I think this should be done in the same way as for Meshes. We
> > discussed the following design:
> >
> > 1. Reading a single file "foo.xml" results in each process reading the
> > entire file but skipping data located on another process as determined
> > by local_range. This is what is implemented now for meshes (followed
> > by communication and mesh partitioning). The difference for vectors
> > would be that no extra communication is necessary.
> >
>
> OK.
>
> > 2. Reading a set of files "foo*.xml" results in each process reading
> > its portion stored in "foo%d.xml" % p. The File interface then needs
> > to check for the occurence of '*' and figure out the correct file name
> > based on its process number.
> >
>
> I think that are a number of advantages to having a single .xml that
> points to the 'sub-files'. An obvious advantage is that we won't need to
> distinguish between cases 1 and 2 when reading in a vector.
>
> Garth

I don't feel strongly about either option, but if we go for the
master-file/sub-file design I think we should do the same for vectors
and meshes.

The master file could look something like this for vectors:

  <distributed_vector size="1024" num_partitions="16">
    <sub_vector partition="0" file="foo_0.xml" offset="0"/>
    <sub_vector partition="1" file="foo_1.xml" offset="64"/>
    <sub_vector partition="2" file="foo_2.xml" offset="128"/>
    ...
  </distributed_vector>

For meshes, we can do this:

  <distributed_mesh num_partitions="16">
    <sub_mesh partition="0" file="foo_0.xml"/>
    <sub_vector partition="1" file="foo_1.xml"/>
    <sub_vector partition="2" file="foo_2.xml"/>
    ...
  </distributed_mesh>

--
Anders

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