# How to do remd simulation using single Vga?

**URL:** <https://gromacs.bioexcel.eu/t/how-to-do-remd-simulation-using-single-vga/1413>\
**Category:** User discussions\
**Created:** [January 9, 2021, 3:47pm UTC](https://gromacs.bioexcel.eu/t/how-to-do-remd-simulation-using-single-vga/1413 "2021-01-09T15:47:15Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![sam](https://avatars.discourse-cdn.com/v4/letter/s/5f9b8f/32.png) [@sam](https://gromacs.bioexcel.eu/u/sam)\
**Post date:** [January 9, 2021, 3:47pm UTC](https://gromacs.bioexcel.eu/t/how-to-do-remd-simulation-using-single-vga/1413/1 "2021-01-09T15:47:15Z")

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GROMACS version:2020.4

I have laptop with RTX … Is it possible to use my VGA card with 6 cores in doing 6 numbers of temperature and what is the command  
i tried this command

> for i in 0 1 2 3 4 5
> 
> do
> 
> gmx grompp -f nvt\_$i.mdp -c nvt.gro -t nvt.cpt -p topol.top -o remd$i.tpr -maxwarn 10;
> 
> done
> 
> mpirun -np 6 mdrun\_mpi -v -deffnm remd -multi 6 -replex 500

but i got

> It seems that there is no lamd running on the host user.
> 
> This indicates that the LAM/MPI runtime environment is not operating.  
> The LAM/MPI runtime environment is necessary for the “mpirun” command.
> 
> Please run the “lamboot” command the start the LAM/MPI runtime  
> environment. See the LAM/MPI documentation for how to invoke  
> “lamboot” across multiple machines.

---

<div class="post-metadata">

**Author:** ![cblau](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/cblau/32/5_2.png) [@cblau](https://gromacs.bioexcel.eu/u/cblau)\
**Post date:** [January 12, 2021, 3:22pm UTC](https://gromacs.bioexcel.eu/t/how-to-do-remd-simulation-using-single-vga/1413/2 "2021-01-12T15:22:11Z")

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Hi Sam,

to run the simulations in parallel for the replica exchange protocol, GROMACS relies on `MPI`, which you would have to set up on your machine.

You can do that by running  
`lamboot`  
before you start your simulation.

If you run  
`ps -Alef | grep lamd`  
you can check if the respective demon is running that manages the MPI simulations.

If you cannot run `lamboot`, you might have to run  
`sudo apt install lam-runtime`

Then your simulation should just run just fine.