# Error during production MDrun

**URL:** <https://gromacs.bioexcel.eu/t/error-during-production-mdrun/7951>\
**Category:** User discussions\
**Created:** [January 1, 2024, 6:11am UTC](https://gromacs.bioexcel.eu/t/error-during-production-mdrun/7951 "2024-01-01T06:11:00Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![SP06](https://avatars.discourse-cdn.com/v4/letter/s/ecb155/32.png) [@SP06](https://gromacs.bioexcel.eu/u/SP06)\
**Post date:** [January 1, 2024, 6:11am UTC](https://gromacs.bioexcel.eu/t/error-during-production-mdrun/7951/1 "2024-01-01T06:11:00Z")

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GROMACS version:2021.4  
GROMACS modification: Yes/No  
Here post your question I am simulating my protein in cyclohexane solvent. On the final production MD run, i got the following error-  
Fatal error:  
The X-size of the box (5.875432) times the triclinic skew factor (1.000000) is  
smaller than the number of DD cells (4) times the smallest allowed cell size  
(1.477750)  
How to resolve this, what size of the box should I use (I am used cubic box of size 1.0 nm) ?

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**Author:** ![milosz.wieczor](https://avatars.discourse-cdn.com/v4/letter/m/b19c9b/32.png) [@milosz.wieczor](https://gromacs.bioexcel.eu/u/milosz.wieczor)\
**Post date:** [January 3, 2024, 3:34pm UTC](https://gromacs.bioexcel.eu/t/error-during-production-mdrun/7951/2 "2024-01-03T15:34:06Z")

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You’re not using a cubic box of size 1.0 nm, your box’ X-dimension is almost 6 nm.

It seems that you’re using too many CPUs for the size of your system, try requesting fewer of them or use `-ntmpi`/`-ntomp` to command `gmx mdrun` to use fewer.

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**Author:** ![SP06](https://avatars.discourse-cdn.com/v4/letter/s/ecb155/32.png) [@SP06](https://gromacs.bioexcel.eu/u/SP06)\
**Post date:** [January 5, 2024, 5:28pm UTC](https://gromacs.bioexcel.eu/t/error-during-production-mdrun/7951/3 "2024-01-05T17:28:59Z")

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Thank you @milosz.wieczor