Anders Logg wrote: > On Sun, Mar 14, 2010 at 08:45:39AM +0000, Garth N. Wells wrote: >> >> Anders Logg wrote: >>> On Sun, Mar 14, 2010 at 08:35:32AM +0000, Garth N. Wells wrote: >>>> 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, [email protected] wrote: >>>>>>>> ------------------------------------------------------------ >>>>>>>> revno: 4635 >>>>>>>> committer: Garth N. Wells <[email protected]> >>>>>>>> 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'. >>> Yes, but then maybe it's not needed since the local size will be >>> available in the local files (which can be standard XML vector data). >>> >>> But then won't the master files always be trivial? The only extra >>> information that is contained in the master file is the total size, >>> and the number of partitions (which will only be used to check that it >>> matches the actual number of processes). >>> >> The master file is the definitive file. Say a program is run with 4 >> processes, and then with 2. The files vector_0.xml, vector_1.xml, >> vector_2.xml and vector_3.xml will be floating around, but which files >> make up the vector? The master file will point to vector_0.xml and >> vector_1.xml. > > I don't understand how that would work. Would it repartition the > entire vector or just use the first two? >
It would read the first two. What the program does with them from that point onwards is separate issue. >> Also, there should be no need to check that the number of 'partitions' >> matches the number of processes. > > That seems to be the only real use of having a master file, at least > the only extra information contained in the master file and not > contained in the local files. > The master file *defines* which files are the sub files. For example, a collection of .xml files could be read by a single process program, just like ParaView does. Garth > -- > Anders > > >> Garth >> >> >>>> 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> >>>>> _______________________________________________ Mailing list: https://launchpad.net/~dolfin Post to : [email protected] Unsubscribe : https://launchpad.net/~dolfin More help : https://help.launchpad.net/ListHelp
