Re: Parallel Sieve Of Eratosthenes

Le 01/07/2024 à 02:02, Lawrence D'Oliveiro a écrit :

On Sun, 30 Jun 2024 18:36:45 +0200, J-P. Rosen wrote:
 

That's because in your first version, you call the child within the
accept statement. Therefore you wait for the value to go to the end of
the pipeline before processing the next value.
Try to copy the number to a variable, and call the child after the end
of the accept. This will give you 100% CPU time usage.
>
BTW, you don't need an access type. Just use a declare block to create
the child after the first accept.

 Thanks for the comments, how about this slight rework of the first
version. It does seem faster, but I’m not sure it’s as fast as the second
version.

That's better, but as a general principle, you should move as much as you can out of the rendezvous (minimize critical sequences). For example:
           accept next_int(i : integer) do
               my_prime := i;
           end next_int;
           Text_IO.Put_line(integer'image(my_prime));  -- moved
           declare
               subchild : offspring;
               ii : integer;
           begin
               loop
                   accept next_int(i : integer) do
                       ii := i;
                   end next_int;
                   if ii mod my_prime /= 0 then --moved
                       subchild.next_int(ii);
                   end if;
               end loop;
--
J-P. Rosen
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