Only permit rank0 to mkdir when -d flag specified

[pdmullen]

PR Summary

Evidently, @bprather and I are among the few who actually use the -d flag. This flag enables users to send all output data to a specified directory, e.g.,

mpiexec -n 99999999999 ./my_exe -i my_input -d /my_scratch/my_run

I have found on several occasions that when firing up a multi-rank job, I get a crash with an accompanying error message indicating that there was an error in creating the directory.

I think this issue is related to a race condition wherein multiple ranks were trying to create the same directory. The changes in this MR permit only rank 0 to create the directory. Then we call an MPI_Barrier in the unlikely chance that one rank tries to chdir into a directory not yet created.

PR Checklist

• Code passes cpplint
• New features are documented.
• Adds a test for any bugs fixed. Adds tests for new features.
• Code is formatted
• Changes are summarized in CHANGELOG.md
• CI has been triggered on Darwin for performance regression tests.
• Docs build
• (@lanl.gov employees) Update copyright on changed files

[bprather]

The code looks great. I should be able to pull tomorrow & test that it fixes the crash for me

[Yurlungur]

Nice catch!

[pgrete]

Looks like it was the bug we suspected.