Allow to create backends with a single core

[mihaiconstantin]

This is regarding Jonas' request in #53 (comment).

[mihaiconstantin]

To maintain backwards compatibility, I propose we implement this as a package option, say cores_minimum. Currently, parabar shows a warning if less than two cores are used, so it would be sensible to set cores_minimum = 2 as default.

Then, users can customize this to their needs as follows:

# Adjust the minimum number of backend cores.
set_option("cores_minimum", 1)

# Start a backend.
backend <- start_backend(cores = 1)

# At this point this will not show a warning anymore.

# Dispose the backend.
stop_backed(backend)

Similarly:

# Adjust the minimum number of backend cores.
set_option("cores_minimum", 4)

# Start a backend.
backend <- start_backend(cores = 2)

# This will show a warning and, should they are available, set to `4` cores.

# Dispose the backend.
stop_backed(backend)

Would this address the issue, @jmbh?

[jmbh]

Hi Mihia,

Apologies for the slow response!

Thanks, yes, that sounds like a good solution and it would be great if you could include it in the package!

Best wishes,
Jonas