[Users] meeting minutes for 2016-12-12

[Frank Loeffler]

On Thu, Dec 15, 2016 at 10:05:54AM -0600, Roland Haas wrote:
>Note that the many failures on comet and gordon seem to be related to
>file corruption when producing ASCII Carpet output (though
>CarpetIOASCII seems bug free). The corruption goes away if I force
>flushing of the buffers after each line (using std::endl instead of
>"\n").

The garbled output, if not coming from two processes, look like a race. 
If it is, an explicit flush after output wouldn't solve the problem, but 
instead 'just' make it less likely to happen.

>This happens on both comet and gordon which use different
>versions of the intel compiler (2015 and 2013) and different gcc
>compilers (for the C++ library). It almost sounds like a file system
>issue (they both use similar scratch file systems since they are both
>at SDSC) and the issue goes away if I run in $HOME rather than 
>$SCRATCH.

Yes. This smells like the filesystem or OS not invalidating a cache 
after a (probably cached) write to a file happened. The sysadmins should 
either know about it, or should be interested in it. If this is indeed 
the case, it should be possible to generate a simple test case 
show-casing the problem.

Frank
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