6781900f98
entire explanation ;-) )
Our Abaqus friends just pointed out another bug to me. We have the
"-x" option to orterun to export environment variables to
newly-started processes. However, it doesn't work if the environment
variable is already set in the target environment. For example:
mpirun -x LD_LIBRARY_PATH -np 2 a.out
The app context correctly contains LD_LIBRARY_PATH and its value, and
that app context correctly propagates out to the orted and is present
when we fork/exec a.out. However, if LD_LIBRARY_PATH is already set
in the newly-started process' environment, the fork pls won't override
it with the value from the app context.
It really only has to do with the ordering of arguments in
ompi_environ_merge() -- when merging to env arrays together, we
"prefer" one set to the other if there are duplicate names. I think
that if the user wants to override variables (even variables like
LD_LIBRARY_PATH), we should let them -- it's necessary for some
applications (like in Abaqus' case). If they screw it up, it's their
fault (e.g., setting some LD_LIBRARY_PATH that won't work).
That being said, we should *not* allow them to override specific MCA
parameters that are necessary for startup -- that's easy to accomplish
by setting up that stuff *after* we merge in the context app
environment.
Also note that I am *only* speaking about the fork pls here -- so this
only applies to started ORTE job processes, not the orted.
So an easy re-order to do the following:
env_copy = merge(environ and context->app)
ompi_setenv(...MCA params necessary for startup..., env_copy)
execve(..., env_copy)
does what we want.
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...more to write here
should be a short file, referring to the real docs.