Just as there's an option to run the code in Serial on a single machine, it would be nice to have an option to run the code with some specified number of slaves on a single machine. I would imagine it looking something like this (though the name of the implementation isn't amazing):

pypy my_mrs_program.py -I SingleMachine --mrs-num-slaves 10 [other options, but no need to specify a port]

Agreed that this would be a nice feature.