# compute smd/ulsph/num/neighs command

## Syntax

``` LAMMPS
compute ID group-ID smd/ulsph/num/neighs
```

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

## Examples

``` LAMMPS
compute 1 all smd/ulsph/num/neighs
```

## Description

Define a computation that returns the number of neighbor particles
inside of the smoothing kernel radius 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 returns a per-particle vector, which can be accessed by any
command that uses per-particle values from a compute as input. See the
[Howto output](Howto_output) page for an overview of LAMMPS output
options.

The per-particle values will be given dimensionless, see [units](units).

## 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/num/neighs](compute_smd_tlsph_num_neighs)

## Default

none