Re: Is there an Ada compiler whose Ada.Numerics.Generic_Elementary_Functions.Log(Base=>10, X=>variable) is efficient?

[jonathan <johnscpg@googlemail.com>]

On Feb 15, 10:58 am, Colin Paul Gloster <Colin_Paul_Glos...@ACM.org>
wrote:
> Hello,
>
> I have been improving a program by suppressing C++ in it. After
> speeding it up a lot by making changes, I have found one considerable
> part which calls a library routine, which is unfortunately very slow
> as provided as standard with a number of Ada compilers but which is
> very fast with implementations of other languages....

Here is my own bench ... easier to play with:

with ada.numerics.generic_elementary_functions;
with text_io; use text_io;

procedure log_bench is

  type Real is digits 15;
  package Math is new ada.numerics.generic_elementary_functions
(Real);
  use Math;
  x, y : Real := 0.1;

  -- might (or might not!) be faster to use:
  --    log_base_10 (x) = log_base_10_of_e * log_base_e (x)

  Log_base_10_of_e : constant := 0.434_294_481_903_251_827_651_129;

begin

  for i in 1 .. 1_000_000 loop
    x := x + Log_base_10_of_e * Log (y);
    y := y + 0.0000000000001;
  end loop;
  put (Real'Image(x));

end log_bench;


gnatmake  gnatnp -O2 -march=native log_bench.adb