[Scons-users] Add `--parallel` option to automatically use all CPU threads

[Fred Wright]

On Wed, 6 Apr 2022, Bill Deegan wrote:

> There's no need to add an additional option for this.
> If you can programmatically detect the # of cores (in python), you can do
> this in your own code via SetOption('num_jobs', NUMBER  HERE) and even
> check if num_jobs is set to 1 which is the current default value and if so
> then set it to the actual number of cores.
>
> What might work as a SCons default behavior change though, is to have -j's
> default value be 0 and if 0, use some logic to set based on # of available
> cores.

MacPorts does something like this, though it also looks at the amount of 
RAM.  I think it assumes that you should have at least N+1 GiB of RAM for 
N parallel processes.

The parallel default seems reasonable, and it can be overridden when 
needed by explicitly giving -j1.  But that wouldn't work if your 
suggestion in the first paragraph were used.  So perhaps SetOption() 
shouldn't be able to override an explicit setting on the command line.

Fred Wright