Add performance documentation for WeightedIndex

[sicking]

Also includes a small documentation improvement for Uniform

[sicking]

Fixes the WeightedIndex-specific parts of #116

[sicking]

I had to revert the changes to Uniform in order to pass tests. The problem is that we create two struct.Uniform.html files, in different directories, so getting both to link to external files correctly is tricky. And while only one of the two files is linked is used (I think), the tests will complain about broken links in the other one.

This is probably fixable somehow, but since this changed was tangential to this PR anyway, I'll leave it for a separate PR.

[dhardy]

Thanks.

What was the missing changes?

[dhardy]

This is not correct:
https://play.rust-lang.org/?gist=5a60d248126851f2e4e7fefeec3ac24e&version=stable&mode=debug&edition=2015

[sicking]

I'm not sure which part you're saying is is incorrect. Uniform<X> certainly has size, but it doesn't allocate memory (from the heap).

I'm also not counting the "inline" part of Vec<X> as allocation, which is why those bytes are not mentioned. Nor things like alingment bytes.

Generally the easiest way to account for the "inline" parts of objects is to use mem::size_of<WeightedIndex<X>>(). That'll account for all those bits, but won't account for memory allocations, which is why I focused more on talking about memory allocations.

Do you have any suggestions for wording to make that more clear?

[dhardy]

True; I skim read. However #116 asks for documentation on memory usage, not allocations, and as far as I'm aware this is what is usually more interesting (though one can separate heap and stack usage).

[sicking]

I guess both are useful in different situations. I pushed an updated version, let me know if it matches what you had in mind.

[sicking]

What was the missing changes?

Not sure what you mean here?

[dhardy]

You mentioned you had to revert some changes but those aren't in the commit, so I wondered what they are?

[sicking]

You mentioned you had to revert some changes but those aren't in the commit, so I wondered what they are?

Ah. I wanted to add the "See the [module documentation] on how to implement [Uniform] range sampling for a custom type." text, which we currently have on the traits, also to the documentation of the Uniform struct.