For some time, ORTE has had the ability to launch daemons on all nodes prior to launching an application. It has largely been used outside of the OMPI community, and so was never explicitly turned "on" inside OMPI releases. Nevertheless, the code has been there.
Allowing VM launches does not require ANY changes to existing PLM components. All that was required was to have orterun launch the daemons as a separate call to orte_plm.spawn -prior- to launching the applications. The rest of the VM support code resides in the rmaps framework:
(a) a check when asked to map a job to see if it is the daemon job, and
(b) a separate "setup_virtual_machine" mapper in the rmaps base that creates the required map so the PLM's will do the right thing.
In order to support those users who have no RM allocation but like to give the allocation in the form of a -host or -hostfile argument to their application, there is a little more code in orterun and the setup_virtual_machine mapper to capture information passed in that manner.
This has been tested with rsh and slurm environments, and, since there is nothing environment-specific in the implementation, should work in others as well - but needs to be proven.
This commit was SVN r24524.
dc6f616599