OCaml: measure execution time in toplevel

Question

How should we measure the execution time of a function in the OCaml toplevel?

Answer 1

As @user3075773 says, you can use Sys.time. However note that it returns processor time (CPU time). More often I want to know the wall clock time (elapsed time). You can get this from Unix.gettimeofday:

let time f x =
    let t = Unix.gettimeofday () in
    let fx = f x in
    Printf.printf "execution elapsed time: %f sec\n"
        (Unix.gettimeofday () -. t);
    fx