performance check key-value pair access using - direct array - array through key array and match function - Hashtbl

gistfile1.ml

type currency_t =  JPY | USD | EUR | AUD | GBP

let to_int ccy = match ccy with
  | JPY -> 0
  | USD -> 1
  | EUR -> 2
  | AUD -> 3
  | GBP -> 4

let currencies = [|JPY;USD;EUR;AUD;GBP|]

let currency_length = 5

let a = Array.init currency_length (fun i -> 10 * i) 

let memo =
  let h = Hashtbl.create 5 in
  (Hashtbl.add h  JPY 0;
   Hashtbl.add h  USD 10;
   Hashtbl.add h  EUR 20;
   Hashtbl.add h  AUD 30;
   Hashtbl.add h  GBP 40;
  h)

let loop_pure_array n =
  let max_i = currency_length - 1 in
  let result = ref 0.0 in
  for i=1 to n do
    for j=0 to max_i do
      result := !result +. (float_of_int (a.(j)))
    done
  done;
  !result 

let loop_array n =
  let max_i = currency_length - 1 in
  let result = ref 0.0 in
  for i=1 to n do
    for j=0 to max_i do
      result := !result +. (float_of_int a.((to_int (currencies.(j)))))
    done
  done;
  !result 

let loop_hash n =
  let max_i = currency_length - 1 in
  let result = ref 0.0 in
  for i=1 to n do
    for j=0 to max_i do
      result := !result +. (float_of_int (Hashtbl.find memo (currencies.(j)))) 
    done
  done;
  !result 

let iteration_number =
  (int_of_string (Sys.argv.(1)))

let target =
  (Sys.argv.(2))

let f = match target with
  | "hash" -> loop_hash 
  | "pure_array" -> loop_pure_array
  | "array" -> loop_array 
  | _ -> failwith "hoge"

let _ =
  let result = (f iteration_number) in
  Printf.printf "result = %f\n" result