[mpich-discuss] Hydra issues

[Dave Goodell]

On Aug 26, 2009, at 9:19 AM, Dave Goodell wrote:

> On Aug 26, 2009, at 8:58 AM, Scott Atchley wrote:
>
>> Ok, I was not patient enough. If I let it run, it eventually  
>> starts. The actual walltime is nearly the same as when I use  
>> proxies, but the stdout is delayed until the application completes.
>
> I think I know why this happens.  It ought to be fixed once I finish  
> up some Hydra I/O work that was mostly done by one of our students  
> this summer.  The work is basically done and lives on a development  
> branch but it needs a little bit of cleanup and to be rebased onto  
> the current trunk.

I was mistaken on this particular issue.  There was another buffering  
issue that we ran into during the student's work and I was thinking of  
that one.  There isn't any current hydra-side fix for this that I know  
of.

However you could use one of the various workarounds for this, such as  
an LD_PRELOADed setvbuf call: http://lists.gnu.org/archive/html/bug-coreutils/2008-11/msg00164.html

With a little thought and man page reading someone could probably come  
up with the Mac equivalent if that were also needed.   
DYLD_INSERT_LIBRARIES is the equivalent of LD_PRELOAD on Darwin, IIRC.

We could also maybe include this workaround approach in hydra via a  
command-line option (for platforms where it is possible).   
"mpiexec.hydra --disable-output-buffering ..." or some such option.

-Dave