Source file profiler_units.ml

open! Core
open Poly

type t =
  | Words
  | Seconds
  | Nanoseconds
  | Int
[@@deriving sexp, compare]

let to_string t = t |> [%sexp_of: t] |> Sexp.to_string
let of_string str = str |> Sexp.of_string |> [%of_sexp: t]

let format_int t x =
  let float_to_string = Float.to_string_hum ~strip_zero:true ~decimals:2 in
  let rec loop x_div suffixes =
    match suffixes with
    | [] -> assert false
    | [ s ] -> float_to_string x_div ^ s
    | s :: ss ->
      if Float.abs x_div < 1000.
      then float_to_string x_div ^ s
      else loop (x_div /. 1000.) ss
  in
  let x = float x in
  match t with
  | Seconds -> float_to_string x ^ "s"
  | Nanoseconds -> loop x [ "ns"; "us"; "ms"; "s" ]
  | Words -> loop x [ "w"; "kw"; "Mw"; "Gw" ]
  | Int -> loop x [ ""; "e3"; "e6"; "e9"; "e12" ]
;;

let%test_unit "format_int" =
  let long = 5_000_001_000_000_001L |> Int64.to_int_exn in
  List.iter
    [ long, Nanoseconds, "5_000_001s"
    ; -100_100, Nanoseconds, "-100.1us"
    ; -99_010, Nanoseconds, "-99.01us"
    ; -99_001, Nanoseconds, "-99us"
    ; 201, Nanoseconds, "201ns"
    ; 4_500_000, Nanoseconds, "4.5ms"
    ; 1_000, Seconds, "1_000s"
    ; 100, Words, "100w"
    ; -235, Int, "-235"
    ]
    ~f:(fun (num, units, str) -> [%test_eq: string] (format_int units num) str)
;;