Comment by jcparkyn
11 hours ago
> Have you benchmarked any real workloads?
Nothing "real", just the synthetic benchmarks in the ./benchmarks dir.
Unnecessary copies are definitely a risk, and there's certain code patterns that are much harder for my interpreter to detect and remove. E.g. the nbodies has lots of modifications to dicts stored in arrays, and is also the only benchmark that loses to Python.
The other big performance limitation with my implementation is just the cost of atomic reference counting, and that's the main tradeoff versus deep cloning to pass between threads. There would definitely be room to improve this with better reference counting optimizations though.
There is some prior work on mitigating the performance cost of immutability that you might be interested in. For example, Clojure's persistent vectors allow fast modifications without destroying the original vector, because internally they're wide trees rather than just linear arrays of memory. This allows for assignments to be implemented without a copy of the full vector. https://hypirion.com/musings/understanding-persistent-vector...