Optimized to rush.
Optimizations used:
with_capacityto reduce allocs.BufReaderto improve file reading to reduce waiting for the disk..par_bridge()to use all CPU cores.DashMapto optimize concurrent write in aHashMapwith the results.with_capacity_and_shard_amountto reduce allocs and concurrent access to keys in same shard.lto = trueandstrip = trueto get a 614 KB to try to fit caches and better optimized machine code.