MNT: Change default optimization levels

[greglucas]

Don't optimize windows, increase optimization on linux/mac

• Add meson default buildtype=release (O3)
• Add -ffast-math flag if compiler supports it

Profiling

Doing some quick timing examples locally to see what kind of difference this makes and it is larger than I expected, with ~3x difference. Windows friends, I'm sorry, perhaps someone with a Windows machine can debug how to fix the tests when we start including compiler optimizations.

Example script

import time

import numpy as np

from pymsis import msis


lons = np.arange(90)
lats = np.arange(37)
alts = np.arange(72) + 200
dates = np.datetime64("2010-01-01T00:00") + np.timedelta64(1, "h") * np.arange(6)

start = time.perf_counter()
for _ in range(20):
    output = msis.run(dates, lons, lats, alts)
end = time.perf_counter()
print("Time elapsed (20 calls): ", end - start)

Results

FFLAGS	Time (s)
-Ofast	8.16
-O3	11.78
-O2	12.34
-O1	13.34
-O0	23.5