Use minimum instead of mean for benchmarks

[alecloudenback]

Especially for noisy CI runs, the times are likely very noisy from background tasks, etc. E.g. this talk discusses what to use when benchmarking and concludes minimum is generally preferred: https://www.youtube.com/watch?v=vrfYLlR8X8k&t=951s

[serenity4]

I agree that minimum time would be preferable, but unfortunately I did not find an easy way to do this for the Python benchmarks (haven't look at R). Most timing tools I found returned the average values without exposing individual trials. Any ideas? cc @MatthewCaseres

[MatthewCaseres]

For Python people seem to have a strategy that works - https://stackoverflow.com/questions/33588041/timeit-module-get-fastest-and-slowest-loop For R the discussion here backs up the idea that we should rather focus on minimum than on mean, should be possible - https://adv-r.hadley.nz/perf-measure.html#benchmark-results

Question is how many trials to perform, this is something we can probably tune by hand a bit so the CI doesn't take forever.

I know Python I hard-coded the number 20 in a few places - https://github.com/actuarialopensource/benchmarks/blob/main/Python/basicterm.py#L14

[serenity4]

Fixed in #45.