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From: Pierre Weis <weis@pauillac.inria.fr>
Message-Id: <200310081448.QAA14841@pauillac.inria.fr>
Subject: Re: [Caml-list] what is the functional way to solve this problem?
In-Reply-To: <20031002145327.GA4690@roke.freak> from Michal Moskal at "Oct 2, 103 04:53:27 pm"
To: malekith@pld-linux.org (Michal Moskal)
Date: Wed, 8 Oct 2003 16:48:09 +0200 (MET DST)
Cc: ramb@sonic.net, caml-list@pauillac.inria.fr
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Hi Michal,

[...]
> Key points of my implementation:
[...]
> 3. It doesn't use Scanf. For such linear task as this Scanf takes 10 or
>    more times to parse input then actual computations.
[...]
> -- 
> : Michal Moskal :: http://www.kernel.pl/~malekith : GCS {C,UL}++++$ a? !tv
> : When in doubt, use brute force. -- Ken Thompson : {E-,w}-- {b++,e}>+++ h

I'm sorry to report that I was so puzzled by your number 3) key point,
that I tested your code and a ``purely scanf'' version to see this
``10 or more times to parse'' behaviour; I didn't notice any runtime
difference between the two (native code compiled) versions. Am I
missing something ?

Could you please try to use the following version of your read
function, and report the runtime difference between your hand written
code ?

(BTW, I compiled the 2 programs using ocamlopt -unsafe -inline 9)

let read () =
  try
    Scanf.bscanf Scanf.Scanning.stdib " %c" (function
    | 'D' ->
        Scanf.bscanf Scanf.Scanning.stdib " %d %d %s"
        (fun x y s -> D (x, y, s))
    | 'F' ->
        Scanf.bscanf Scanf.Scanning.stdib " %d %s"
        (fun x s -> F (x, s))
    | _ -> invalid_arg "read")
  with End_of_file -> Eof

You should also replace
(*
  let l = read_line () in
  let (dh, fh) = Scanf.sscanf l "R 0 %[^\n]" start in
*)
by

  let (dh, fh) = Scanf.bscanf Scanf.Scanning.stdib "R 0 %s@\n" start in

Looking forward for reading from you,

Pierre Weis

INRIA, Projet Cristal, Pierre.Weis@inria.fr, http://pauillac.inria.fr/~weis/


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