CHAINERMN_FORCE_ABORT_ON_EXCEPTIONS
If this variable is set to a non-empty value, ChainerMN installs a global hook to Python's sys.excepthook to call
MPI_Abort()
when an unhandled exception occurs. Seefaq-global-except-hook
ChainerMN issue #236 may also help to understand the problem.
chainermn.global_except_hook.add_hook