# Simulation won't run, time spent in pair searching

**URL:** <https://gromacs.bioexcel.eu/t/simulation-wont-run-time-spent-in-pair-searching/176>\
**Category:** User discussions\
**Created:** [May 24, 2020, 1:50pm UTC](https://gromacs.bioexcel.eu/t/simulation-wont-run-time-spent-in-pair-searching/176 "2020-05-24T13:50:32Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![ca10nt](https://avatars.discourse-cdn.com/v4/letter/c/eb9ed0/32.png) [@ca10nt](https://gromacs.bioexcel.eu/u/ca10nt)\
**Post date:** [May 24, 2020, 1:50pm UTC](https://gromacs.bioexcel.eu/t/simulation-wont-run-time-spent-in-pair-searching/176/1 "2020-05-24T13:50:33Z")

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GROMACS version: 2020.1-Ubuntu  
GROMACS modification: No  
Here post your question  
‘NOTE: 74 % of the run time was spent in pair search,  
you might want to increase nstlist (this has no effect on accuracy)’

This ‘error’ is outputted when running an energy minimization mdrun. The .mdp nstlist parameter is 1. What is the likely problem?

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**Author:** ![jalemkul](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/jalemkul/32/18_2.png) [@jalemkul](https://gromacs.bioexcel.eu/u/jalemkul)\
**Post date:** [May 24, 2020, 2:49pm UTC](https://gromacs.bioexcel.eu/t/simulation-wont-run-time-spent-in-pair-searching/176/2 "2020-05-24T14:49:04Z")

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You should not rely on performance estimates from energy minimization. The note from `mdrun` is generic output from any invocation of the command but is not important in this case.