Added mem-dbg as optional feature

[LucaCappelletti94]

Mem-dbg is a crate that allows to compute the size of a struct. I have added the derives through the crate as an optional feature, so as to use it to compare this implementation with others easily.

Cheers!

[LucaCappelletti94]

FYI, the errors are caused by the CI configuration being old. Consider updating it.

[alecmocatta]

Thanks for this! Let me know when done and will merge despite the outdated CI.

[LucaCappelletti94]

Hi @alecmocatta, sure - I am running some benchmarks so I may add some other small edits.

[LucaCappelletti94]

Why are you checking whether the estimates are three-sorted? I see that you run a binary search but that requires the estimates to be completely sorted, and I recently discovered that the estimates provided from the HLL++ paper are not sorted (they nearly are). I will be providing a fix for that shortly.

streaming_algorithms/src/distinct/consts.rs

Lines 33 to 45 in 99522db

	fn is_three_sorted<T>(data: &[T]) -> bool
	where
	T: PartialOrd + Debug,
	{
	data.windows(3).all(|w| {
	let ret = w[0].partial_cmp(&w[2]).unwrap() != Ordering::Greater;
	if !ret {
	println!("{:?}", w);
	}
	ret
	})
	}
	}