# reset_timestep command

## Syntax

``` LAMMPS
reset_timestep N keyword values ...
```

-   N = timestep number

-   zero or more keyword/value pairs may be appended

-   keyword = *time*

        *time* value = atime
           atime = accumulated simulation time

## Examples

``` LAMMPS
reset_timestep 0
reset_timestep 4000000
reset_timestep 1000 time 100.0
```

## Description

Set the timestep counter to the specified value. This command usually
comes after the timestep has been set by reading a restart file via the
[read_restart](read_restart) command, or a previous simulation run or
minimization advanced the timestep.

The optional *time* keyword allows to also set the accumulated
simulation time. This is usually the number of timesteps times the size
of the timestep, but when using variable size timesteps with [fix
dt/reset](fix_dt_reset) it can differ.

The [read_data](read_data) and [create_box](create_box) commands set the
timestep to 0; the [read_restart](read_restart) command sets the
timestep to the value it had when the restart file was written. The same
applies to the accumulated simulation time.

## Restrictions

This command cannot be used when any fixes are defined that keep track
of elapsed time to perform certain kinds of time-dependent operations.
Examples are the [fix deposit](fix_deposit) and [fix
dt/reset](fix_dt_reset) commands. The former adds atoms on specific
timesteps. The latter keeps track of accumulated time.

Various fixes use the current timestep to calculate related quantities.
If the timestep is reset, this may produce unexpected behavior, but
LAMMPS allows the fixes to be defined even if the timestep is reset. For
example, commands which thermostat the system, e.g. [fix nvt](fix_nh),
allow you to specify a target temperature which ramps from Tstart to
Tstop which may persist over several runs. If you change the timestep,
you may induce an instantaneous change in the target temperature.

Resetting the timestep clears flags for [computes](compute) that may
have calculated some quantity from a previous run. This means these
quantity cannot be accessed by a variable in between runs until a new
run is performed. See the [variable](variable) command for more details.

## Related commands

[rerun](rerun), [timestep](timestep), [fix dt/reset](fix_dt_reset)

## Default

none