clarified OMP_NUM_THREADS

[zerothi]

Removed description of possible deprecation of OMP_NUM_THREADS.

After discussion in #825 it was agreed to:

• lax the deprecation warning, OMP_NUM_THREADS will always be a fall-bock.
• Clarified with a simple example on how to do different regions of thread-counts.

[zerothi]

What is not clear from the current document is how the BLIS_IC_NT and friends interact with the default number of threads. I didn't mention it currently.

I think this solves #825

[devinamatthews]

Setting any of the BLIS_XX_NT values will override BLIS_NUM_THREADS and OMP_NUM_THREADS. Unset BLIS_XX_NT values are taken as 1. (@fgvanzee check me on this)

[fgvanzee]

What is not clear from the current document is how the BLIS_IC_NT and friends interact with the default number of threads. I didn't mention it currently.

I think this solves #825

This is actually already mentioned in the document under "Specifying multithreading." It's even in bold.

Note: Please be aware of what happens if you try to specify both the automatic and manual ways, as it could otherwise confuse new users. Here are the important points:

• Regardless of which of the three methods is used, if multithreading is specified via both the automatic and manual ways, the values set via the manual way will always take precedence.

[zerothi]

Sorry for the mislead, I just didn't see it in the mentioned section. But I suppose that is not necessary, so please forget my comment.

I think the PR still remains final, let me know if you need any changes, I'll amend!

[fgvanzee]

Sorry for the mislead, I just didn't see it in the mentioned section. But I suppose that is not necessary, so please forget my comment.

I think the PR still remains final, let me know if you need any changes, I'll amend!

No problem. Thanks for your feedback!