Re: What is faster Ada or C?

[dewar@gnat.com (Robert Dewar)]

Jacob Sparre Andersen <sparre@nbi.dk> wrote in message news:<3C10F77E.6BDD9A3B@nbi.dk>...
> When I look at the corresponding assembler code (gnatgcc
> -S/g++ -S) I can see that GNU C++ inlines the square root
> function, while GNU Ada doesn't.


You seem to be assuming that the function called square root in C++
and the function called square root in Ada
are the same function, presumably because their names
are similar, and both are usable in your context, but they
are not at all the same routine. The Ada routine has additional
semantics not present in the C++ routine (e.g.
the handling of -0.0 which is required to return -0.0).
Is this just a theoretical issue? Not at all. Look at the
coding for Sqrt in a-ngelfu.adb:

   function Sqrt (X : Float_Type'Base) return 
                                     Float_Type'Base is
   begin
      if X < 0.0 then
         raise Argument_Error;

      --  Special case Sqrt (0.0) to preserve possible 
      --  minus sign per IEEE

      elsif X = 0.0 then
         return X;

      end if;

      return Float_Type'Base (Aux.Sqrt (Double (X)));
   end Sqrt;

Those extra tests take significant time. Now one can sit
back and say "Ada is a junk language, it insists on testing
for errors at runtime, and in giving accurate IEEE results,
and I don't need either", but that's not a very reasonable
position given that if you like you can easily call the
C routine directly, since Ada, unlike other languages,
carefully defines the syntax and semantics of calling routines written
in other languages :-)