Awesome

We expect 3 threads for outer parallelism and 2 threads for inner

outer ICC / inner GCC

outer_tid	outer_tnum	outer_get_max_threads	inner_tid	inner_tnum	inner_get_num_threads	inner_get_max_threads
[18076]	[0]	[3]	[18076]	[0]	[1]	[3]
[18078]	[1]	[3]	[18078]	[0]	[1]	[3]
[18079]	[2]	[3]	[18079]	[0]	[1]	[3]

3 threads for outer as expected (3 unique values for outer_num)
Only 1 for inner. Seems that gnu openmp is aware it's in nested parallelism which is disable by default.

outer GCC / inner ICC

outer_tid	outer_tnum	outer_get_max_threads	inner_tid	inner_tnum	inner_get_num_threads	inner_get_max_threads
[18158]	[0]	[3]	[18158]	[0]	[2]	[2]
[18158]	[0]	[3]	[18162]	[1]	[2]	[2]
[18160]	[2]	[3]	[18160]	[0]	[4]	[4]
[18160]	[2]	[3]	[18164]	[2]	[4]	[4]
[18160]	[2]	[3]	[18163]	[1]	[4]	[4]
[18160]	[2]	[3]	[18165]	[3]	[4]	[4]
[18159]	[1]	[3]	[18168]	[3]	[4]	[4]
[18159]	[1]	[3]	[18167]	[2]	[4]	[4]
[18159]	[1]	[3]	[18166]	[1]	[4]	[4]
[18159]	[1]	[3]	[18159]	[0]	[4]	[4]

3 threads for outer as expected.
In master thread of outer: 2 inner threads as expected
In other threads: as many as possible (4 is the value returned by omp_get_max_threads before entering the parallel region)