gring VS RoaringBitmap

Not super obscure, but I remember that one specific time when circular-linked-list made a lot of sense to use, well I wanted to use it so I used it.

I had a bunch of API keys with poor expiry documentation and implementation, so to find out if a key expired it had to be used. I put it in a main "keys.pop loop" and all methods below tried to use the key. If HTTP response was (some another obscure HTTP response code like) 505, I simply called `continue;` in the loop to jump to another, without caring at all where I was before.

https://github.com/atedja/gring

I was recently reading about Roaring https://roaringbitmap.org/ which is a highly optimized compressed bitset implementation. I reccomend reading about it if you are interested in this sort of thing. The talk at https://roaringbitmap.org/talks/ is especially good.

However, I would love compressed (not just packed) bitsets too, which is something different to me. I would make it another class with a similar interface, based on something like roaring. It doesn't need to be in the standard, but it would be nice if the API was a such that one could easily swap implementations.

As an aside if you find yourself having to compute them on the fly, know that the Roaring Bitmaps libraries is the way to go [1]. The bitmaps are compressed, and can be streamed directly into SIMD computations (batching XORs and popcnts 256 bits wide!). The Jaccard index is just intersection_len / union_len [2] away

[1] https://roaringbitmap.org/

[2] https://roaringbitmap.readthedocs.io/en/latest/#roaringbitma...

Use a two stage approach, with a bloom/cuckoo filter stored as a https://roaringbitmap.org/ in memory. Then a secondary key/value store on disk (bolt or anything else).

As an aside, if you're dealing with large bit sets, you might also want to evaluate Roaring Bitmaps.

Sidetracking a bit the conversation. What a coincidence that the author (Lemire) is also represented on Today's #1 "Ask HN: What are some cool but obscure data structures you know about?" as he is the main contributor of RoaringBitmap https://github.com/RoaringBitmap/RoaringBitmap and one of the main authors of the data structure.