bita VS xxHash

Built this cdc tool for software update of embedded (Linux) systems and have deployed it with good enough performance on a couple of arm CPUs; https://github.com/oll3/bita

Though main goal has been keeping data usage low rather than speed up.

Nice write up. rsync is great as an application but I found it more cumbersome to use when wanting to integrate it into my own application. There's librsync but the documentation is threadbare and it requires an rsync server to run. I found bita/bitar (https://github.com/oll3/bita) which is inspired by rsync & family. It works more like zsync which leverages HTTP Range requests so it doesn't require anything running on the server to get chunks. Works like a treat using s3/b2 storage to serve files and get incremental differential updates on the client side!

Very cool, thanks for sharing. I did a deep dive in the past into various syncing/binary diff protocols and really liked zsync. It was probably my top choice for the application I was designing but I ended up not using it. The library I did use is called bita: https://github.com/oll3/bita. It is inspired by the same family of projects as zsync. The main advantage I found with bita is that the core logic is encapsulated in a library so that you don’t only have to use the binaries but can integrate it directly into an application. I’d be curious to know if that’s in the plans for KySync.

> GPU Hash Table?

How bad would performance have suffered if you sha256'd the lines to build the map? I'm going to guess "badly"?

Maybe something like this in CUDA: https://github.com/Cyan4973/xxHash ?

Examples of fast, simple hashes that are independent enough includes murmur, xxHash, Fowler–Noll–Vo hash function and many others

If you're only using the hash for non-cryptographic applications, there are much faster hashes: https://github.com/Cyan4973/xxHash

I found the benchmark result of AMD ryzen 5950X

But what's the catch, you're thinking ? Well, it is a bit slower than its counterparts when it comes to deserializing (and marginally faster for serializing). To achieve smaller footprint, it uses a few tricks and notably a custom hash table to deduplicate strings. This comes at a cost of course (even when featuring xxHash to speed things up), but keeps the slowdown reasonable (I think).

Non cryptographic hashes has collisions, for example, assume you having content like "abcdefg" which hashed value is "123", in case of weak hash algorithm some other content like "abcdefZ" can also have a hash "123" which basically means such hash function is failed to be unique fingerprint of particular content. BLAKE3 for example can do 6-7Gb/s which make it pretty fast and secure. If your requirement accepts collision with defined error rate, I would advise you to take a look at XXH3 if you need very snappy hash algorithm, which can run at pace or RAM access (30GB/s+), but again, run tests at particular equipment you targeting, may be AES hardware accelerated MeowHash will serve you better.