From: "Alain Coetmeur" Newsgroups: comp.parallel.mpi Subject: Re: Can multiple processes write to a single file? Date: Fri, 11 Dec 1998 19:12:28 +0100 Organization: Informatique-CDC Message-Id: <74rne2$g5n5@puligny.idt.cdc.fr> References: Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 8bit Robert G. Jacobs a écrit dans le message ... >I have an MPI f90 code that has a routine in which I'd like to have each >MPI process write a number of records into a direct access >unformatted file. Each process writes to the same file, but different >records. The code runs to completion without error, but only 1 process's >writes get updated in the file. The remaining records are unchanged, even >though the code says it's writing them. f90 I don't know... unix I know better. if you guaranty that there is no ovelapping this should work, when the file is open in read/write mode (maybe write only, but i'm not sure) . preallocate the total size before... anyway ther may be something strange with f90 since you ask for it... and this should alredy work... maybe am wrong. anyway this is a typical use of MPI-IO system. If you are using MPI-Ch or a MPI that support MPI-IO you can take advantage of any optimisation in the lower layer of the filesystem... >So is it possible to have more than one process write records to a file >simultaneously on an SGI Origin 2000 computer? On the Cray T3E I can fix >this by using "assign -m on" but this feature isn't implemented on the >SGI. Any ideas on how to allow this? Thanks. ??? on SGI you can have XFS that must have some parallel IO extension IMHO.