[gmx-users] Using -multidir option on Cray (aprun)

[Suman Chakrabarty]

Hello!

I am trying to use the -multidir feature of mdrun for setting up a REMD
simulation on a Cray XT system. It requires the "aprun" launcher to spawn
the parallel processes rather than the usual mpirun (which I have
successfully used with -multidir before).

I am using the 2019.3 version of Gromacs and I can successfully run normal
parallel Gromacs jobs (without -multidir) in this system.

I have the following setup in my submission script:

exec1="/home/chs1/soft/GMX2019.3/bin/mdrun_mpi -ntomp 1 -deffnm nvt
-multidir remd_{1..2}"

aprun -n 64 -N32 -d1 ${exec1}


I get the following error message from all 64 MPI processes:

MPI rank:    8 (out of 64)

Source file: src/gromacs/mdrun/multisim.cpp (line 77)

To run mdrun in multiple simulation mode, more then one actual simulation
is required. The single simulation case is not supported.

I don't understand why Gromacs is treating this as "single simulation
case"! Can anybody with more experience in using the -multidir option in a
Cray system suggest any solution to this problem? Thanks.


Regards,

Suman.