# Built-in launchers
**Row** includes built-in support for MPI, OpenMP, and Rayon via the launchers
`"mpi"`, `"openmp"`, and `"rayon"`. These have been tested on the [built-in
clusters](../clusters/built-in.md). You may need to add new configurations
for your specific cluster or adjust the `none` launcher to match your system.
Execute [`row show launchers`](../row/show/launchers.md) to see the current
launcher configuration.
## OpenMP
Set `launchers = ["openmp"]` to prefix the action's command with:
```bash
OMP_NUM_THREADS={T}
```
where `{T}` is the number of `threads_per_process` requested.
## Rayon
Set `launchers = ["rayon"]` to prefix the action's command with:
```bash
RAYON_NUM_THREADS={T}
```
where `{T}` is the number of `threads_per_process` requested.
## Hybrid OpenMP/MPI
When using OpenMP/MPI hybrid applications, place `"openmp"` first in the list of
launchers (`launchers = ["openmp", "mpi"]`) to generate the appropriate command:
```bash
OMP_NUM_THREADS={T} srun --ntasks=N --cpus-per-task=T command $directory
```