# Unable to run REMD simulation

**URL:** <https://gromacs.bioexcel.eu/t/unable-to-run-remd-simulation/237>\
**Category:** User discussions\
**Created:** [June 3, 2020, 3:58pm UTC](https://gromacs.bioexcel.eu/t/unable-to-run-remd-simulation/237 "2020-06-03T15:58:43Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![peter.mawanga](https://avatars.discourse-cdn.com/v4/letter/p/ccd318/32.png) [@peter.mawanga](https://gromacs.bioexcel.eu/u/peter.mawanga)\
**Post date:** [June 3, 2020, 3:58pm UTC](https://gromacs.bioexcel.eu/t/unable-to-run-remd-simulation/237/1 "2020-06-03T15:58:44Z")

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GROMACS version: 2019.5  
GROMACS modification: No

Dear users,

I am trying to run a REMD simulation, with the replica files in the working directory having names like testrun\_1.tpr, testrun\_2.tpr, etc.

However, upon running the command below with SLURM architecture:

mpirun gmx\_mpi mdrun -s testrun\_.tpr -v -deffnm testrun\_ -replex 500 \>\> replex\_1.log

I get errors like:

Error in user input:  
Invalid command-line options  
In command-line option -s  
File ‘testrun\_.tpr’ (or ‘testrun\_’) does not exist or is not accessible.  
The file could not be opened.  
Reason: No such file or directory  
(call to fopen() returned error code 2)

Even the ‘-multi’ option is not being recognized:

Error in user input:  
Invalid command-line options  
In command-line option -s  
File ‘testrun\_.tpr’ does not exist or is not accessible.  
The following extensions were tried to complete the file name:  
.tpr  
Unknown command-line option -multi

Please advise on how to proceed further regarding this. Thanks a lot.

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**Author:** ![mick](https://avatars.discourse-cdn.com/v4/letter/m/f04885/32.png) [@mick](https://gromacs.bioexcel.eu/u/mick)\
**Post date:** [June 7, 2020, 8:25pm UTC](https://gromacs.bioexcel.eu/t/unable-to-run-remd-simulation/237/2 "2020-06-07T20:25:22Z")

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Quick question,

Have you tried placing all of the different tpr’s in different directories and used -multidir? I know in 2020 -multi was removed and you need to use -multidir instead

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**Author:** ![peter.mawanga](https://avatars.discourse-cdn.com/v4/letter/p/ccd318/32.png) [@peter.mawanga](https://gromacs.bioexcel.eu/u/peter.mawanga)\
**Post date:** [June 9, 2020, 11:39am UTC](https://gromacs.bioexcel.eu/t/unable-to-run-remd-simulation/237/3 "2020-06-09T11:39:14Z")

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Hi Mick,

Unfortunately the tutorials (or notes?) available were not very clear, so had to devise something on my own which indeed involved the “-multidir” flag. The command below worked finally:

mpirun gmx\_mpi mdrun -v -deffnm testrun -multidir {1…68} -replex 500 \>\> replex.log

Although I have another question, is it recommended to use the “-multidir” flag for the “grompp” and the typical “mdrun” commands too? Of course, the “-replex” flag will not be present then. Please let me know your thoughts regarding this.

Cheers  
Peter

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**Author:** ![asker1](https://avatars.discourse-cdn.com/v4/letter/a/e0b2c6/32.png) [@asker1](https://gromacs.bioexcel.eu/u/asker1)\
**Post date:** [November 4, 2021, 3:33am UTC](https://gromacs.bioexcel.eu/t/unable-to-run-remd-simulation/237/4 "2021-11-04T03:33:20Z")

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excuse me did you use for loop for this command ?

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**Author:** ![peter.mawanga](https://avatars.discourse-cdn.com/v4/letter/p/ccd318/32.png) [@peter.mawanga](https://gromacs.bioexcel.eu/u/peter.mawanga)\
**Post date:** [December 13, 2021, 6:20pm UTC](https://gromacs.bioexcel.eu/t/unable-to-run-remd-simulation/237/5 "2021-12-13T18:20:08Z")

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No, I executed the command as above.