Cache microarch once found

we use the function get_native_microarchitecture() multiple times in the code and if MPSD_MICROARCH is not defined then it calls archspec and thus pollutes the logs multiple times. We should probably cache the microarch once we find it. There could be multiple ideas for where to store:

• set MPSD_MICROARCH after you find it.
• keep a global vale
• keep it inside the global config_vars dict

We can cache the function return value I think. Then we avoid further global variables:

from functools import cache

@cache
def fib(n):
    if n < 2:
        return n
    return fib(n-1) + fib(n-2)

>>> print([fib(n) for n in range(10)])
# Output: [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]

I am not sure when cache was introduced. In any case, there is lru_cache which has been around for ages (python 3.2 or so).

mentioned in merge request !90 (merged)

closed with merge request !90 (merged)

mentioned in commit 5fb82222