Unknown command-line option -multi

GROMACS version: 2020.4

i tried to use - multi option but got

Unknown command-line option -multi

in this command

mpirun -np 3 gmx mdrun -s remd_$i.tpr -multi 3 -replex 1000 -deffnm remd_

The -multi option was removed some time ago and was replaced by -multidir to initiate many simulations in different directories.

Thanks for replying but excuse me when can i use different directories ? can this be an option for the command not a mandatory

See the “Running multi-simulations” section of the user guide