Re: Not good for Ada endorsement

[Egil H H <ehh.public@gmail.com>]

On Thursday, July 8, 2021 at 7:38:19 PM UTC+2, Luke A. Guest wrote:
> On 08/07/2021 12:12, Jeffrey R. Carter wrote: 
> 
> >> He also uses clang's -Ofast option to compile for speed over size. 
> > 
> > Going back to 64-bit integers gives 1999; with -gnatp, 2098 
> >
> I've uploaded my version here 
> https://github.com/Lucretia/Primes/tree/add-optimised-ada/PrimeAda/solution_2 
> 
> It's as straight a conversion from the C++ to Ada. I intend to keep 
> optimising it.

On my computer, at least, GNAT is not happy about incrementing Number by 2
in the inner loop. I get a bit better performance by modifying the check to

      if Number mod 2 /= 0 and then Sieve.Bits(Index_Type(Number)) then

and then incrementing Number by 1.

Or even rewriting to a for-loop

         Is_Prime : for Foo in Index_Type (Factor)..Sieve.Size loop
            if Foo mod 2 /= 0 and then Sieve.Bits (Foo) then
               Factor := Integer(Foo);
               exit Is_Prime;
            end if;
         end loop Is_Prime;