Serialise accelerator tasks only on local executor?

[SamStudio8]

Is there an idiom for setting maxForks to 1 for a particular process but only when the executor is local? As Nextflow does not manage GPU devices (to prevent scheduling processes to the same GPU device), I would like to automatically configure a workflow to serialise GPU tasks for local executors -- without user intervention.

I note that it is one of the directives that cannot be set dynamically (so no closures); is there a trick I am missing? Otherwise it would be useful if one could cap the number of accelerators in the executor.$local config like you can with cpus and memory, which would have the same effect without having to use maxForks.

[pditommaso]

Only for a specific process or for the overall pipeline (ie. run only one task at time)?

[SamStudio8]

For any process that needs a GPU. I want to be able to do something like this:

process {
    withLabel:gpu {
        maxForks = { process.executor == "local" ? 1 : null }
    }
}

[pditommaso]

Nope, this cannot be done. You should use a profile, but I guess that is not what you are trying to achieve

[bentsherman]

You would have to add another label e.g. label 'local' to your local processes so that you can select them using withLabel.