I know it's wrong, but I don't think it is forbidden.... (which I guess is what you are saying).
On Tue, Feb 2, 2010 at 5:31 PM, Jeff Squyres <jsquy...@cisco.com> wrote: > +1 on Nick's responses. > > AFAIK, if you don't mind getting garbage in the output file, it should be > fine to do. Specifically: it should not cause OS issues (crash, reboot, > corrupted filesystem, etc.) to do this -- but the file contents will likely > be garbage. > > That being said, this situation likely falls into the "Doc, it hurts when I > do this..." category. Meaning: you know it's wrong, so you probably > shouldn't be doing it anyway. :-) > > > On Feb 2, 2010, at 4:50 PM, Nicolas Bock wrote: > >> Hi Laurence, >> >> I don't know whether it's as bad as a deadly sin, but for us parallel writes >> are a huge problem and we get complete garbage in the file. Take a look at: >> >> Implementing MPI-IO Atomic Mode and Shared File Pointers Using MPI One-Sided >> Communication, Robert Latham,Robert Ross, Rajeev Thakur, International >> Journal of High Performance Computing Applications, 21, 132 (2007). >> >> They describe an implemenation of a "mutex" like object in MPI. If you >> protect writes to the file with an exclusive lock you can serialize the >> writes and make use of NFS's close to open cache coherence. >> >> nick >> >> >> On Tue, Feb 2, 2010 at 08:27, Laurence Marks <l-ma...@northwestern.edu> >> wrote: >> I have a question concerning having many processors in a mpi job all >> write to the same file -- not using mpi calls but with standard >> fortran I/O. I know that this can lead to consistency issues, but it >> can also lead to OS issues with some flavors of nfs. >> >> At least in fortran, there is nothing "wrong" with doing this. My >> question is whether this is "One of the Seven Deadly Sins" of mpi >> programming, or just frowned on. (That is, it should be OK even if it >> leads to nonsense files, and not lead to OS issues.) If it is a sin, I >> would appreciate a link to where this is spelt out in some "official" >> document or similar. >> >> -- >> Laurence Marks >> Department of Materials Science and Engineering >> MSE Rm 2036 Cook Hall >> 2220 N Campus Drive >> Northwestern University >> Evanston, IL 60208, USA >> Tel: (847) 491-3996 Fax: (847) 491-7820 >> email: L-marks at northwestern dot edu >> Web: www.numis.northwestern.edu >> Chair, Commission on Electron Crystallography of IUCR >> www.numis.northwestern.edu/ >> Electron crystallography is the branch of science that uses electron >> scattering and imaging to study the structure of matter. >> _______________________________________________ >> users mailing list >> us...@open-mpi.org >> http://www.open-mpi.org/mailman/listinfo.cgi/users >> >> _______________________________________________ >> users mailing list >> us...@open-mpi.org >> http://www.open-mpi.org/mailman/listinfo.cgi/users > > > -- > Jeff Squyres > jsquy...@cisco.com > > > _______________________________________________ > users mailing list > us...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/users > -- Laurence Marks Department of Materials Science and Engineering MSE Rm 2036 Cook Hall 2220 N Campus Drive Northwestern University Evanston, IL 60208, USA Tel: (847) 491-3996 Fax: (847) 491-7820 email: L-marks at northwestern dot edu Web: www.numis.northwestern.edu Chair, Commission on Electron Crystallography of IUCR www.numis.northwestern.edu/ Electron crystallography is the branch of science that uses electron scattering and imaging to study the structure of matter.
