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, an

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 boolean transformations and popcnts 256 bits wide!). The Jaccard index is just intersection_len / union_len [2] away Of note: the author of that library is none other than Daniel Lemire [3], whose articles pop up quite often on HN [1] https://roaringbitmap.org/ https://roaringbitmap.org/ [2] https://roaringbitmap.readthedocs.io/en/latest/#roaringbitmap.RoaringBitmap.intersection_len https://roaringbitmap.readthedocs.io/en/latest/#roaringbitma... [3] https://lemire.me/blog/ https://lemire.me/blog/