I built mpich 3.3.2 with 

./configure -with-ibverbs=/usr --with-ibverbs-include=/usr/include --with-ibverbs-lib=/usr/lib64 --with-pmi=simple --prefix=/home/admin/hammo
nd/mpich

Running through the queue with a command line

/home/admin/hammond/mpich/bin/mpiexec -n 8 -machinefile ./machinefile myapp -i electron.in

I see:

srwxr-xr-x   1 root root   0 Mar 30 17:33 sock.pmi2.5442.0

So I guess it is using pmi2.

But the slowness compared to srun is the same.