Yeah I kind of think authors didn't conduct a thorough-enough literature review here. There are well-known relations between number of hash functions you use and the FPR, cache-blocking and register-blocking are classic techniques (Cache-, Hash-, and Space-Efficient Bloom Filters by Putze et. al), and there are even ways of generating patterns from only a single hash function that works well (shamelessly shilling my own blogpost on the topic: https://save-buffer.github.io/bloom_filter.html)
I also find the use of atomics to build the filter confusing here. If you're doing a join, you're presumably doing a batch of hashes, so it'd be much more efficient to partition your Bloom filter, lock the partitions, and do a bulk insertion.
I also find the use of atomics to build the filter confusing here. If you're doing a join, you're presumably doing a batch of hashes, so it'd be much more efficient to partition your Bloom filter, lock the partitions, and do a bulk insertion.