On Thu, Mar 2, 2017 at 4:10 PM, Dave Täht <d...@taht.net> wrote: > As for speeding up hashing, I've been looking over various algorithms to > do that for years now, I'm open to suggestions. The fastest new ones > tend to depend on co-processor support. The fastest I've seen relies on > the CRC32 instruction which is only in some intel platforms.
This is an area where I have a fair amount of experience. It is a misconception that CRC is a good hash function. It is good at detecting errors but has poor avalanche performance. What are the requirements for this hashing function? - How much data is being hashed? (I would guess a limited number of bytes rather than an entire packet payload.) - What is the typical number of hash table buckets? Must it be a power of 2? Or are you willing to make it a prime number? Assuming you can afford a 1KB lookup table I would suggest the SBox hash in figure four of this article: http://papa.bretmulvey.com/post/124028832958/hash-functions The virtue of a prime number of buckets is that when you mod your 32-bit hash value to get a bucket index you harvest _all_ of the entropy in the hash, not just the entropy in the bits you preserve. /john _______________________________________________ Lede-dev mailing list Lede-dev@lists.infradead.org http://lists.infradead.org/mailman/listinfo/lede-dev
