# Extending simulation which has simulated annealing

**URL:** <https://gromacs.bioexcel.eu/t/extending-simulation-which-has-simulated-annealing/2736>\
**Category:** User discussions\
**Tags:** mdp-parameters, mdrun\
**Created:** [August 25, 2021, 11:20am UTC](https://gromacs.bioexcel.eu/t/extending-simulation-which-has-simulated-annealing/2736 "2021-08-25T11:20:01Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![VedMahajan](https://avatars.discourse-cdn.com/v4/letter/v/f04885/32.png) [@VedMahajan](https://gromacs.bioexcel.eu/u/VedMahajan)\
**Post date:** [August 25, 2021, 11:20am UTC](https://gromacs.bioexcel.eu/t/extending-simulation-which-has-simulated-annealing/2736/1 "2021-08-25T11:20:01Z")

</div>

GROMACS version: 2020.4  
GROMACS modification: No

Hello,

I have to do a simulation which in which I have to change the temperature of the system. I have included this in my mdp file:

```auto
; Temperature coupling is on
tcoupl = nose-hoover ; modified Berendsen thermostat
tc-grps = system ; two coupling groups - more accurate
tau_t = 0.4 ; time constant, in ps
ref_t = 240 ; reference temperature, one for each group, in K

; Simulated Annealing
annealing = single
annealing-npoints = 2
annealing-temp = 240 80 ; temperature decreases from 240 to 80
annealing-time = 0 2000 ; temperatre decreases from 240K at time = 0 ps to 90K at time = 2000 ps (2 ns)

```

My simulation that I am going to run is with a much lower cooling rate and can go as long as or even longer than `1.6 microseconds`.

My question is if at all due to walltime limitations I cannot finish my simulation and I have to continue it, do I have to change the mdp file’s simulated annealing section or will gromacs take care of it it self when I just use `convert-tpr` to change the tpr file using the `state.cpt` file?

If I have to change what is the easiest way to find how to find the new initial temperature?

One more query I have is, if a `20 ns simulation` takes say `4 hrs`, will a `100ns` simulation of the same system take `20hrs`? Like does it scale linearly or not?

Awaiting your response.

Thank you.