Number of cpus needs better management

[ajstewart]

Currently the number of cpus in the parallelised parts is somewhat arbitrary, it would be good to have control in the user config, or in the non user settings to manage concurrent jobs.

[srggrs]

Not sure why we need this. Anyhow the number of CPUs is set always the total logical cores -1. Why you would like to control this?

[ajstewart]

It's usually nice to have some control over it. E.g. running it locally maybe I don't want it to use all cores so it would be good to have an easy user option to set the number. I agree if you have a dedicated machine then you can get away with the n - 1.

To me it seems standard to include some sort of ncpu option to the user.

[ajstewart]

I haven't tested it in this case but in the past I've had diminishing returns with machines that have hyper threading enabled as well, so sometimes it's more efficient to use less.

[ddobie]

Closing as outdated - #750 is more up-to-date.