# A question about flag: -multi **URL:** \ **Category:** User discussions\ **Tags:** mdrun\ **Created:** [July 20, 2022, 8:36am UTC](https://gromacs.bioexcel.eu/t/a-question-about-flag-multi/4479 "2022-07-20T08:36:51Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![bdx](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/bdx/32/1568_2.png) [@bdx](https://gromacs.bioexcel.eu/u/bdx)\ **Post date:** [July 20, 2022, 8:36am UTC](https://gromacs.bioexcel.eu/t/a-question-about-flag-multi/4479/1 "2022-07-20T08:36:51Z")
GROMACS version:2022.2 GROMACS modification: No I am now running T-REMD simulation using the following bash script: ![Screenshot from 2022-07-20 10-36-23](https://europe1.discourse-cdn.com/flex017/uploads/bioexcel1/original/2X/6/657130edb5765f357abdadfb50f7b29c5946f5c6.png) but the terminal shows ‘Unknown command-line option -multi’. Is the problem caused by the version of GROMACS (I wrote the script following a tutorial， the version of GROMACS used in that tutorial is 2018)? How to solve this? Thanks! ---
**Author:** ![alevilla](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/alevilla/32/439_2.png) [@alevilla](https://gromacs.bioexcel.eu/u/alevilla)\ **Post date:** [July 25, 2022, 1:25pm UTC](https://gromacs.bioexcel.eu/t/a-question-about-flag-multi/4479/2 "2022-07-25T13:25:33Z")
Hi, The option -multi is not available since 2019. From 2019 for a replica-exchange simulations, you can use the option `-replex` and `-multidir`. See more here for details [Useful mdrun features — GROMACS 2022.2 documentation](https://manual.gromacs.org/current/user-guide/mdrun-features.html?highlight=replica-exchange). \Alessandra ---
**Author:** ![bdx](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/bdx/32/1568_2.png) [@bdx](https://gromacs.bioexcel.eu/u/bdx)\ **Post date:** [July 27, 2022, 7:10am UTC](https://gromacs.bioexcel.eu/t/a-question-about-flag-multi/4479/3 "2022-07-27T07:10:28Z")
Dear Alessandra， Thanks so much for your help Sincerely