dolfin team mailing list archive

["Garth N. Wells" <gnw20@xxxxxxxxx>]

Anders Logg wrote:
> 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>
>


Looks good, except 'offset' should be 'size', or 'local_size'.

Garth

> 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