update nvm.sh to detect number of cores on aix

[gdams]

Currently nvm is detecting the number of processors available for building on aix. I have managed to improve this to get the number of threads

[ljharb]

I'm not sure I understand - does AIX abstract over "processors" such that programs should be using N - 1 threads in order to avoid locking up the machine?

[gdams]

There is no reason that it should be any different to other platforms. When I added AIX I couldn't get a command that counted threads easily but have now found that this command does exactly that

[ljharb]

Right, but the purpose of this check is to ensure that there is always at least one CPU available to process commands besides nvm install -s, to avoid locking up the machine. Using the thread count will not ensure there is always at least one processor available.

[gdams]

Is that not why you subtract 1 at the end?

[ljharb]

Yes. But by starting with the number of threads, we might have 4 CPUs and 20 threads, and we need to only ever run 3 processes in that case.

[gdams]

@gibfahn that is correct

[gdams]

essentially, before I could only get the number of physical cpu's... now I can get the number of CPU cores

[ljharb]

That's a fair point; perhaps the variable name needs renaming.

[gdams]

it should probably be NVM_CPU_CORES?

[ljharb]

Sounds good

[gdams]

@ljharb Is this change ready to approve?

[ljharb]

@GeorgeAdams95 after a rebase due to #1326, the code blockers would be removed, but conceptually we'd been discussing whether this change actually makes sense. The intention here is to count processor cores, not threads.

[gdams]

@ljharb This PR does exactly that! before it was counting physical cpu's now it counts cores.
e.g on an AIX machine with 2 quad core processorrs:

Before the output was 2
Now it is 8

[ljharb]

Thanks for the explanation! LGTM, pending a rebase.

[gdams]

@ljharb updated PTAL