ego
RoaringBitmap
ego | RoaringBitmap | |
---|---|---|
1 | 24 | |
56 | 3,390 | |
- | 0.8% | |
4.0 | 8.5 | |
4 months ago | 12 days ago | |
OCaml | Java | |
GNU General Public License v3.0 only | Apache License 2.0 |
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ego
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Ask HN: What are some 'cool' but obscure data structures you know about?
Shameless plug, I also maintain an OCaml implementation of egraphs (named ego) at https://github.com/verse-lab/ego
While the most popular implementation at the moment seems to be egg in Rust, I find that OCaml serves as a much more ergonomic environment for quickly prototyping out uses of egraphs in practice. As a bonus, ego also shares the same logical interface as egg itself, so once you've finalised your designs, you shouldn't have much trouble porting them to egg if you need the performance gains.
RoaringBitmap
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Iterating over Bit Sets Quickly
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.
- Roaring Bitmaps
- Roaring bitmaps are compressed bitmaps, can be 100x faster
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What feature would you like to remove in C++26?
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.
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Jaccard Index
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...
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Looking for fast, space-efficient key-lookup
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).
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BitSet Vs BigInteger
As an aside, if you're dealing with large bit sets, you might also want to evaluate Roaring Bitmaps.
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Negative Incentives in Academic Research
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.
- Ask HN: What are some 'cool' but obscure data structures you know about?
- Roaring bitmaps: A better compressed bitset
What are some alternatives?
PSI - Private Set Intersection Cardinality protocol based on ECDH and Bloom Filters
HyperMinHash-java - Union, intersection, and set cardinality in loglog space
sdsl-lite - Succinct Data Structure Library 2.0
lucene - Apache Lucene open-source search software
us - An alternative interface to Sia
CQEngine - Ultra-fast SQL-like queries on Java collections
RVS_Generic_Swift_Toolbox - A Collection Of Various Swift Tools, Like Extensions and Utilities
Primes - Prime Number Projects in C#/C++/Python
Folly - An open-source C++ library developed and used at Facebook.
Feign - Feign makes writing java http clients easier
multiversion-concurrency-control - Implementation of multiversion concurrency control, Raft, Left Right concurrency Hashmaps and a multi consumer multi producer Ringbuffer, concurrent and parallel load-balanced loops, parallel actors implementation in Main.java, Actor2.java and a parallel interpreter
maven-compiler-plugin - Apache Maven Compiler Plugin