The input data is sequential. I don’t understand Rust but if the code is doing what’s written there, “simple multiplicative hash and perform a simple analysis

The input data is sequential. I don’t understand Rust but if the code is doing what’s written there, “simple multiplicative hash and perform a simple analysis on the buckets – say, compute the sum of minimums among buckets” it’s possible to improve substantially. They don’t need to move these megabytes of elements between collections. I would split the input across a few CPU cores, compute per-bucket minimums in parallel on each core, when all completed aggregate minimums across all cores, then compute sum of the results. Multiplicative hash and the final sum should be possible to vectorize on most computers. Updating per-bucket minimum is probably impossible to vectorize (technically AVX512 set has the required instructions but I’m not sure these are efficient) but there’re much fewer buckets than input numbers, which means arrays with per-bucket minimums are likely to fit in caches.