# compute smd/ulsph/strain/rate command

## Syntax

``` LAMMPS
compute ID group-ID smd/ulsph/strain/rate
```

-   ID, group-ID are documented in [compute](compute) command
-   smd/ulsph/strain/rate = style name of this compute command

## Examples

``` LAMMPS
compute 1 all smd/ulsph/strain/rate
```

## Description

Define a computation that outputs the rate of the logarithmic strain
tensor for particles interacting via the updated Lagrangian SPH pair
style.

See [this PDF guide](PDF/MACHDYN_LAMMPS_userguide.pdf)\_ to using Smooth
Mach Dynamics in LAMMPS.

## Output info

This compute calculates a per-particle vector of vectors (tensors),
which can be accessed by any command that uses per-particle values from
a compute as input. See the [Howto output](Howto_output) doc page for an
overview of LAMMPS output options.

The values will be given in [units](units) of one over time.

The per-particle vector has 6 entries, corresponding to the xx, yy, zz,
xy, xz, yz components of the symmetric strain rate tensor.

## Restrictions

This compute is part of the MACHDYN package. It is only enabled if
LAMMPS was built with that package. See the [Build
package](Build_package) page for more info.

This compute can only be used for particles which interact with the
updated Lagrangian SPH pair style.

## Related commands

[compute smd/tlsph/strain/rate](compute_smd_tlsph_strain_rate)

## Default

none