{"action":"created","issue":{"url":"https://api.github.com/repos/raffenet/mpich-migrate-test/issues/142","repository_url":"https://api.github.com/repos/raffenet/mpich-migrate-test","labels_url":"https://api.github.com/repos/raffenet/mpich-migrate-test/issues/142/labels{/name}","comments_url":"https://api.github.com/repos/raffenet/mpich-migrate-test/issues/142/comments","events_url":"https://api.github.com/repos/raffenet/mpich-migrate-test/issues/142/events","html_url":"https://github.com/raffenet/mpich-migrate-test/issues/142","id":167970155,"number":142,"title":"Re: [OMPI users] bug in MPI_File_get_position_shared ?","user":{"login":"raffenet","id":1410792,"avatar_url":"https://avatars.githubusercontent.com/u/1410792?v=3","gravatar_id":"","url":"https://api.github.com/users/raffenet","html_url":"https://github.com/raffenet","followers_url":"https://api.github.com/users/raffenet/followers","following_url":"https://api.github.com/users/raffenet/following{/other_user}","gists_url":"https://api.github.com/users/raffenet/gists{/gist_id}","starred_url":"https://api.github.com/users/raffenet/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/raffenet/subscriptions","organizations_url":"https://api.github.com/users/raffenet/orgs","repos_url":"https://api.github.com/users/raffenet/repos","events_url":"https://api.github.com/users/raffenet/events{/privacy}","received_events_url":"https://api.github.com/users/raffenet/received_events","type":"User","site_admin":false},"labels":[],"state":"closed","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":1,"created_at":"2016-07-27T22:18:32Z","updated_at":"2016-07-27T22:18:33Z","closed_at":"2016-07-27T22:18:33Z","body":"**Originally by _Robert Latham <robl@mcs.anl.gov>_ on 2008-09-15 16:03:42 -0500**\n\n___\n\n\nOn Sat, Aug 16, 2008 at 08:05:14AM -0400, Jeff Squyres wrote:\n> On Aug 13, 2008, at 7:06 PM, Yvan Fournier wrote:\n>\n>> I seem to have encountered a bug in MPI-IO, in which\n>> MPI_File_get_position_shared hangs when called by multiple processes  \n>> in\n>> a communicator. It can be illustrated by the following simple test  \n>> case,\n>> in which a file is simply created with C IO, and opened with MPI-IO.\n>> (defining or undefining MY_MPI_IO_BUG on line 5 enables/disables the\n>> bug). From the MPI2 documentation, It seems that all processes should \n>> be\n>> able to call MPI_File_get_position_shared, but if more than one  \n>> process\n>> uses it, it fails. Setting the shared pointer helps, but this should  \n>> not\n>> be necessary, and the code still hangs (in more complete code, after\n>> writing data).\n>>\n>> I encounter the same problem with Open MPI 1.2.6 and MPICH2 1.0.7, so\n>> I may have misread the documentation, but I suspect a ROMIO bug.\n>\n> Bummer.  :-(\n>\n> It would be best to report this directly to the ROMIO maintainers via \n> romio-maint@mcs.anl.gov.  They lurk on this list, but they may not be \n> paying attention to every mail.\n\nHi, that would be me, and yup, as you can see I don't check in too\noften.  \n\nJust to wrap this up, I'm glad you found workarounds.  Shared file\npointers have a certain seductive quality about them, but they are a\npain in the neck to implement in the library.  \n\nYou will almost assuredly scale to larger numbers of processors and\nachieve higher I/O bandwidth if you do just a little bit of work.\nKeep track of file offsets on your own and instead of doing\nindependent I/O use MPI_File_read_at_all or MPI_File_write_at_all.\n\n==rob\n\n-- \nRob Latham\nMathematics and Computer Science Division    A215 0178 EA2D B059 8CDF\nArgonne National Lab, IL USA                 B29D F333 664A 4280 315B"},"comment":{"url":"https://api.github.com/repos/raffenet/mpich-migrate-test/issues/comments/235739110","html_url":"https://github.com/raffenet/mpich-migrate-test/issues/142#issuecomment-235739110","issue_url":"https://api.github.com/repos/raffenet/mpich-migrate-test/issues/142","id":235739110,"user":{"login":"raffenet","id":1410792,"avatar_url":"https://avatars.githubusercontent.com/u/1410792?v=3","gravatar_id":"","url":"https://api.github.com/users/raffenet","html_url":"https://github.com/raffenet","followers_url":"https://api.github.com/users/raffenet/followers","following_url":"https://api.github.com/users/raffenet/following{/other_user}","gists_url":"https://api.github.com/users/raffenet/gists{/gist_id}","starred_url":"https://api.github.com/users/raffenet/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/raffenet/subscriptions","organizations_url":"https://api.github.com/users/raffenet/orgs","repos_url":"https://api.github.com/users/raffenet/repos","events_url":"https://api.github.com/users/raffenet/events{/privacy}","received_events_url":"https://api.github.com/users/raffenet/received_events","type":"User","site_admin":false},"created_at":"2016-07-27T22:18:33Z","updated_at":"2016-07-27T22:18:33Z","body":"**Originally by _Robert Latham_ on 2008-09-15 16:03:42 -0500**\n\n___\n\nThis message has 0 attachment(s)\n\n"}}
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