>From: Bill Long <[log in to unmask]>
>>
>> 1 UK-12 J3/14-174 Allow a file to be connected to more than one unit
>> at one time 8-2-5
>>
>> This sounds like parallel I/O, which I thought was
>> decisively ruled out of the next revision. Am I wrong?
>
>The change was to make it processor dependent whether this is allowed, rather than strictly prohibited as was the case previously. There are no rules specified for how this works. However, it is certainly reasonable and straightforward to have a read-only file connected on multiple images, and this has been done in programs for years. The change was to allow this practice to be not in violation of the standard.
Thank you
> It remains to be seen whether implementations will permit multiple units that allow writing to the same file.
Isn't Cray "assign -m" supposed to do this already [1]?
*quote*
-m setting Special handling of a direct access file
that will be accessed concurrently by
several processes or tasks. Special handling
includes skipping the check that only one
Fortran unit be connected to a unit,
suppressing file truncation to true size by
the I/O buffering routines, and ensuring
that the file is not truncated by the I/O
buffering routines.
Enter either on or off for setting.
*end quote*
I tried to use this on archer.ac.uk with coarrays, but
got unexpected behaviour. My ticket it now with
ARCHER Cray Systems.
Thanks
Anton
[1] http://docs.cray.com/cgi-bin/craydoc.cgi?mode=Show;q=3901;f=/books/S-3901-83/html-S-3901-83//qivklsmg.html
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