Is the printer slow?

[tcoopman]

I have some code that needs to output a large number of dates to a clean format, but I noticed that this was quite slow.

With this benchmark:

open Core;
open Core_bench.Std;

let main = () => {
	let date = CalendarLib.Calendar.from_unixfloat(1000329.);
  Command.run(
    Bench.make_command([
      Bench.Test.create(~name="format", () => ignore(CalendarLib.Printer.Calendar.sprint("%iT%T%z", date))),
    ]),
  );
};

let () = main();

I get this output:

┌────────┬──────────┬─────────┬──────────┬──────────┬────────────┐
│ Name   │ Time/Run │ mWd/Run │ mjWd/Run │ Prom/Run │ Percentage │
├────────┼──────────┼─────────┼──────────┼──────────┼────────────┤
│ format │   2.95us │ 721.26w │    1.07w │    1.07w │    100.00% │
└────────┴──────────┴─────────┴──────────┴──────────┴────────────┘

I'm not sure if you are considering this slow, but to me it was totally unexpected that something like this would take up a large amount of time in my code (after benchmarking almost 50% of my time goes to formatting the date).
When using Calendar_Precise it's even a bit slower (about 0,5 microseconds added)

Am I doing something wrong here? Or is this something that is just slow?

[tcoopman]

I've just done a quick test with ptime Ptime.to_rfc3339(date, ~tz_offset_s=0) and this seems already quite a bit faster.

┌──────────────┬────────────┬─────────┬──────────┬──────────┬────────────┐
│ Name         │   Time/Run │ mWd/Run │ mjWd/Run │ Prom/Run │ Percentage │
├──────────────┼────────────┼─────────┼──────────┼──────────┼────────────┤
│ format       │ 3_017.74ns │ 721.26w │    1.07w │    1.07w │    100.00% │
│ format ptime │   889.41ns │ 215.01w │          │          │     29.47% │
└──────────────┴────────────┴─────────┴──────────┴──────────┴────────────┘

[pmetzger]

Unfortunately, at the moment, we de facto don't have a maintainer for calendar. This means it is likely that until such a person steps up, you may be on your own on this. :(