Ordered dict based on SwissDict

[PallHaraldsson]

Fixes #38163 (not 38135 that got here by accident...).

See this interesting talk, why I chose this implementation:

https://www.youtube.com/watch?v=ncHmEUmJZf4&t=3s

This talk describes the process of design and optimization that starts with std::unordered_map and ends with a new design we call "SwissTable", a 2-level N-way associative hash table. Our implementation of this new design gets 2-3x better performance with significant memory reductions (compared to unordered_map) and is being broadly deployed across Google.

https://abseil.io/blog/20180927-swisstables

[EDIT: Attribution: Code is modified code from @eulerkochy's taken from JuliaCollections/DataStructures.jl.]

[KristofferC]

Testing if CI ok with it. And it seems to be, with "1 failing, 3 pending, and 12 successful checks".

I mean, of course it is since the new Dict you added is not used anywhere.

[PallHaraldsson]

It passes now, with tests, except for a false alarm for freebsd:

command timed out: 3600 seconds without output running [b'sh', b'-c', b'gmake -j6 VERBOSE=1 TAGGED_RELEASE_BANNER="Official https://julialang.org/ release" SRCCACHE=/tmp/srccache USECCACHE=1 JULIA_CPU_TARGET="generic;sandybridge,-xsaveopt,clone_all;haswell,-rdrnd,base(1)" MARCH=x86-64  LLVM_ASSERTIONS=1 FORCE_ASSERTIONS=1 USE_BINARYBUILDER=1  release'], attempting to kill
signal (15): Terminated
in expression starting at compiler/bootstrap.jl:8

[KristofferC]

I am sorry but I am going to close this. There is no desire to have a second implementation of a dictionary with the only difference about it being ordered. People who want such a dictionary can just get the package.

[tpapp]

The code has significant overlap with

https://github.com/JuliaCollections/DataStructures.jl/blob/9f3295869aa976309ef94947029e404c5970dd18/src/swiss_dict.jl

without attribution. @PallHaraldsson, can you please explain? Wording of the PR implies that this is your work, eg

See this interesting talk, why I chose this implementation:

Do you happen to be the same person as @eulerkochy, who implemented this as JuliaCollections/DataStructures.jl#634?

[PallHaraldsson]

without attribution [..] can you please explain?

Yes. This is an important matter to answer, otherwise I wasn't going to (do more at JuliaLang regarding Dicts or) comment on this PR, as it was closed, and made clear it will not be merged, so this is a moot point?

"based on SwissDict" (i.e. Julia code), is/was my imperfect attribution, while I informed the author "I'm copying your implementation to Base" at: JuliaCollections/DataStructures.jl#693 after I started this PR here, before I took Draft status off.

No, I'm not @eulerkochy, I wish! We've corresponded on benchmarking elsewhere prior, where he actually responded (and explained he's busy).

I can see my language confused, while I quoted Google's "SwissTable" that's not the same as the Julia code term SwissDict (I'm not aware that Google uses that term), for the code I used, implying that I reused that Julia code, not me rewriting the C++ code. The code here (his code, mostly) is a reimplementation of "new “Swiss Table” family of hashtables in Abseil", I'm assuming following that design.

I should have been more careful (while mens rea doesn't apply), with taking the Draft status off, or even before, adding precise attribution. I did put in "(from OrderedCollections.jl/DataStructures.jl)" at the very top on my first PR in the series of Dict PRs... #37804. I did NOT specifying a person in any of the cases. I believe I tracked down @oxinabox as the (only?) writer (and yes, we are also different persons) for OrderedDict. So I'm sorry, to you too if this wasn't kosher.

I wouldn't say I'm not taking the MIT license seriously, "only requiring preservation of copyright", and I note their names aren't listed in the files I copied from, thinking you can copy from one MIT licenced project to another MIT licensed (Julia).

If I didn't follow protocol, then please inform me, so I can do better.

[@eulerkochy deserves all the credit for the implementation for SwissDict, and of course Google for the design. It's been said this is "just copy-paste a Dict implementation from a package", so was at least clear to some, while I did a bit more, didn't only rename, I added stuff at the bottom of the file.]

[tpapp]

If I didn't follow protocol, then please inform me, so I can do better.

Generally, when you copy a large body of code from some source, it is common courtesy to be very explicit about that. Not only for legal and ethical reasons; it also informs the readers of the PR that we are talking about code that has already been reviewed and tested.