On Fri, 3 Nov 2023 23:34:49 GMT, Claes Redestad <redes...@openjdk.org> wrote:
> > @cl4es Could you please test > > [this](https://github.com/plokhotnyuk/jsoniter-scala/blob/ba6f4f80deaf0e7a1a95787321de3cc2a232d66d/jsoniter-scala-core/jvm/src/main/scala/com/github/plokhotnyuk/jsoniter_scala/core/JsonReader.scala#L3687) > > function too? It seems that when testing divisibility by 100 we can use > > just one multiplication operation. > > For int values it seems that makes it a few percent faster (1,061 ± 0,017 > ops/us), though we need a variant that works for longs (`GregorianCalendar` > could use this as-is, but not `Year`). Do you have a reference to how they > arrived at these numbers? It might be straightforward to extend it to long > values, and it'd be good to have the theory to reference either way. Thanks for trying and giving the honest feedback! I don't recall exactly but it seems was a kind of playing with `bool f(int n) { return n % 100 == 0; }` on the https://godbolt.org to see assembly generated by latest c++ compilers with `-O3` option and then brute force squeezing a redundant shift operation. I'm not sure that similar is possible for `long` values, so probably it worth to have 2 different methods for `long` and `int` types. I'm even not sure if that function would work for negative `int` values. ------------- PR Comment: https://git.openjdk.org/jdk/pull/16491#issuecomment-1793267652
