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Date: Sat, 26 Feb 2005 20:32:55 -0600
From: Kurt Welgehausen <kwel@kwel.net>
To: caml-list@yquem.inria.fr
Subject: Re: [Caml-list] [Bug] Different behavior bytecode/nativecode
Message-ID: <42213157.mail3Z71XGC6B@kwel.net>
References: <20050227.011343.11780601.Christophe.Troestler@umh.ac.be>
In-Reply-To: <20050227.011343.11780601.Christophe.Troestler@umh.ac.be>
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The problem is in the calculation of cr: it's not really 0.0
in the native code.  I can't tell you why.

let () =
  let w = 400 in
  let invw = 2. /. float w in
  let ci = -1. in
  let cr = 300. *. invw -. 1.5 in
  Printf.printf "%.19f %f -> %i\n" cr ci (add_bit0 cr ci 0);
  print_endline ("invw->"^(Int64.to_string (Int64.bits_of_float invw)));
  print_endline ("cr->"^(Int64.to_string (Int64.bits_of_float cr)));
  print_endline ("ci->"^(Int64.to_string (Int64.bits_of_float ci)))

**kaw<~/ocaml>$ ./mandelbrot
0.0000000000000000000 -1.000000 -> 1
invw->4572414629676717179
cr->0
ci->-4616189618054758400
**kaw<~/ocaml>$ ./mandelbrot.opt 
0.0000000000000000312 -1.000000 -> 0
invw->4572414629676717179
cr->4360047389248061440
ci->-4616189618054758400


Regards