paq8px
RoaringBitmap
| paq8px | RoaringBitmap | |
|---|---|---|
| 4 | 24 | |
| 196 | 3,395 | |
| - | 1.0% | |
| 1.0 | 8.5 | |
| 27 days ago | 25 days ago | |
| C++ | Java | |
| - | Apache License 2.0 |
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paq8px
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In need of crazy compression
paq8px : https://github.com/hxim/paq8px
- Is there any format like .7z or cmix only for archiving pictures?
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Dictionary Compression
paq8px v206 [1] with option "-8art" compresses it to 9,145 bytes using ~2GB of memory in 82s, mostly due to a better pre-training stage.
[1] https://github.com/hxim/paq8px
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?
bzip3 - A better and stronger spiritual successor to BZip2.
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alexandria - Full text search engine powering Alexandria.org - the open search engine.
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Flowable (V6) - A compact and highly efficient workflow and Business Process Management (BPM) platform for developers, system admins and business users.
data.int-map - A map optimized for integer keys