# Performance tuning **URL:** \ **Category:** User discussions\ **Created:** [March 18, 2024, 6:37am UTC](https://gromacs.bioexcel.eu/t/performance-tuning/8636 "2024-03-18T06:37:44Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![xeno007](https://avatars.discourse-cdn.com/v4/letter/x/2bfe46/32.png) [@xeno007](https://gromacs.bioexcel.eu/u/xeno007)\ **Post date:** [March 18, 2024, 6:37am UTC](https://gromacs.bioexcel.eu/t/performance-tuning/8636/1 "2024-03-18T06:37:44Z")
GROMACS version: 2024 GROMACS modification: No Here post your question Hi, I see the following recommendation in my md.log NOTE: 7 % of the run time was spent communicating energies, you might want to increase some nst\* mdp options and when looking at the statistics, I find the following Comm. energies 2688 1 75001 477.624 2439149.256 7.1 What nst\* parameters should i play with to improve this? Are these parameters safely modifiable without any impact in accuracy? comm-mode = Linear nstcomm = 100 ---
**Author:** ![hess](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/hess/32/416_2.png) [@hess](https://gromacs.bioexcel.eu/u/hess)\ **Post date:** [March 19, 2024, 3:58pm UTC](https://gromacs.bioexcel.eu/t/performance-tuning/8636/2 "2024-03-19T15:58:31Z")
There are several parameters that cause energies to be computed and communicated: nstcalcenergy nsttcouple (can be set indirectly by tau\_t) nstpcouple (can be set indirectly by tau\_p) ---
**Author:** ![xeno007](https://avatars.discourse-cdn.com/v4/letter/x/2bfe46/32.png) [@xeno007](https://gromacs.bioexcel.eu/u/xeno007)\ **Post date:** [March 19, 2024, 4:12pm UTC](https://gromacs.bioexcel.eu/t/performance-tuning/8636/3 "2024-03-19T16:12:49Z")
> [@xeno007](#): > > NOTE: 7 % of the run time was spent communicating energies, > you might want to increase some nst\* mdp options 1. Are there possibilities to reduce this by playing with the parameters you have mentioned? 2. will there be any effect on accuracy? 3. For an efficient and optimal run, which function will consume the most %time in the md.log statistics? ---
**Author:** ![hess](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/hess/32/416_2.png) [@hess](https://gromacs.bioexcel.eu/u/hess)\ **Post date:** [March 19, 2024, 5:29pm UTC](https://gromacs.bioexcel.eu/t/performance-tuning/8636/4 "2024-03-19T17:29:43Z")
In most cases you should be able to adjust the parameters to get better performance with affecting accuracy. But I don’t know which settings you have used. The non-bonded pair calculation and PME usually take the most time. ---
**Author:** ![xeno007](https://avatars.discourse-cdn.com/v4/letter/x/2bfe46/32.png) [@xeno007](https://gromacs.bioexcel.eu/u/xeno007)\ **Post date:** [March 20, 2024, 10:43am UTC](https://gromacs.bioexcel.eu/t/performance-tuning/8636/5 "2024-03-20T10:43:44Z")
In my current setup nst\* parameters looks like this ```auto nstcomm = 100 nstcgsteep = 1000 nstxout = 10000 nstvout = 10000 nstfout = 500000 nstlog = 10000 nstcalcenergy = 100 nstenergy = 10000 nstxout-compressed = 10000 nstlist = 10 ensemble-temperature-setting = constant nsttcouple = 10 nstpcouple = 10 ``` Does this info give any hint on what can be paramter can be tuned? ---
**Author:** ![xeno007](https://avatars.discourse-cdn.com/v4/letter/x/2bfe46/32.png) [@xeno007](https://gromacs.bioexcel.eu/u/xeno007)\ **Post date:** [March 20, 2024, 10:46am UTC](https://gromacs.bioexcel.eu/t/performance-tuning/8636/6 "2024-03-20T10:46:21Z")
> [@hess](#): > > The non-bonded pair calculation and PME usually take the most time. I have Force=52%, PME Mesh \*=20%, PME wait for PP \* = 6% and Comm. energies = 7% ---
**Author:** ![pszilard](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/pszilard/32/21_2.png) [@pszilard](https://gromacs.bioexcel.eu/u/pszilard)\ **Post date:** [March 20, 2024, 12:36pm UTC](https://gromacs.bioexcel.eu/t/performance-tuning/8636/7 "2024-03-20T12:36:00Z")
> [@xeno007](#): > > In my current setup nst\* parameters looks like this > > ```auto > nsttcouple = 10 > nstpcouple = 10 > > ``` > > Does this info give any hint on what can be paramter can be tuned? Those are likely unnecessarily frequent. You can just omit them and _if you have your coupling parameters set correctly_ grompp should pick better values (ideally 50-100). ---
**Author:** ![xeno007](https://avatars.discourse-cdn.com/v4/letter/x/2bfe46/32.png) [@xeno007](https://gromacs.bioexcel.eu/u/xeno007)\ **Post date:** [March 20, 2024, 4:11pm UTC](https://gromacs.bioexcel.eu/t/performance-tuning/8636/8 "2024-03-20T16:11:04Z")
> [@xeno007](#): > > `nstpcouple ` As I see, in my mdp file these paramters are not defined. Reading the documentation, i understand that default value -1 is assumed and grompp has replaced it with 10. Is it recommended to change these values to see if it improves performance? will it change the system definition and lead to inaccurate results? ---
**Author:** ![hess](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/hess/32/416_2.png) [@hess](https://gromacs.bioexcel.eu/u/hess)\ **Post date:** [March 20, 2024, 5:28pm UTC](https://gromacs.bioexcel.eu/t/performance-tuning/8636/9 "2024-03-20T17:28:50Z")
The old default values work like this. Newer grompp versions choose values up to 100 taking into account accuracy needs. What can be used depends on the thermo/barostat and tau values.