# How to use multiple cpu cores for analysis

**URL:** <https://gromacs.bioexcel.eu/t/how-to-use-multiple-cpu-cores-for-analysis/3418>\
**Category:** User discussions\
**Created:** [January 7, 2022, 6:38am UTC](https://gromacs.bioexcel.eu/t/how-to-use-multiple-cpu-cores-for-analysis/3418 "2022-01-07T06:38:56Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![rainbow](https://avatars.discourse-cdn.com/v4/letter/r/7993a0/32.png) [@rainbow](https://gromacs.bioexcel.eu/u/rainbow)\
**Post date:** [January 7, 2022, 6:38am UTC](https://gromacs.bioexcel.eu/t/how-to-use-multiple-cpu-cores-for-analysis/3418/1 "2022-01-07T06:38:56Z")

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GROMACS version: 2021.4  
GROMACS modification: No

Dear gmx users,

I installed gmx\_mpi.  
Can I use CPU multi cores for analyses using gmx\_mpi ?  
I don’t know how to use it.  
For example, I tried  
‘gmx\_mpi trjconv -s md.tpr -f md.xtc -n in.ndx -o md\_PBC.xtc -pbc mol -ur compact’  
but it uses only one CPU core.

Also, I’ve tried this too,  
‘mpirun -np 32 gmx\_mpi trjconv -s md.tpr -f md.xtc -n in.ndx -o md\_PBC.xtc -pbc mol -ur compact’  
, but it doesn’t work.

Please give me some advice.  
Kind Regards,

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**Author:** ![pjohansson](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/pjohansson/32/316_2.png) [@pjohansson](https://gromacs.bioexcel.eu/u/pjohansson)\
**Post date:** [January 7, 2022, 7:26am UTC](https://gromacs.bioexcel.eu/t/how-to-use-multiple-cpu-cores-for-analysis/3418/2 "2022-01-07T07:26:48Z")

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Hi,

I believe that no analysis tools are written for MPI, so using `gmx_mpi` will do nothing for them. A few are accelerated using OpenMP threads but this should be automatic. Just use the standard `gmx` binary.

Regards,  
Petter