Code looks great, I don't have any further comments On Tue, Mar 24, 2020 at 12:21 PM Marco Bodrato <bodr...@mail.dm.unipi.it> wrote:
> Ciao, > > Il 2020-03-24 18:54 Seth Troisi ha scritto: > > On Tue, Mar 24, 2020 at 9:56 AM Marco Bodrato > > <bodr...@mail.dm.unipi.it> wrote: > >> I propose a variation of your patch, you find it attached, on my > >> computer it's faster. > > > > Couple of small notes but otherwise this looks good > > > > +/* NP_SMALL_LIMIT = prevprime (LAST_PRIME ^ 2) */ > > > > In the light of the day this can be bumped slightly to > > prevprime(nextprime(LAST_PRIME)^2) - 1 = 316960 > > I'm not sure. > I mean: with that list of primes we can certify primality up to that > limit, I agree. > But what about the exit condition? The current code consider that a number is prime if(n/prime<prime). > To support n > LAST_PRIME^2, we should add one more branch in the loop. > You are correct I was remembering my code. > > + /* Technically this should be prev_prime(LAST_PRIME ^ 2) */ > > I'd remove this, It's covered by the comment above > Right. > > > + if (q < prime) > > + return t; > > + if (r == 0) > > + break; > > > > Can this be rearranged to > > > > + if (r == 0) > > + break; > > + if (q <= prime) > > + return t; > > I fear it can't. The case t=3, prime=3 would consider 3 a composite. > Moreover I believe that, on some architectures, q can be ready before r > is, so the order Torbjorn used should reduce latency. But I may be wrong > on that point. > > The case t=3 can be healed with an if(t<9) return t; just before the > loop. Then we should measure speed on different platforms. > With the order you propose, we may use > NP_SMALL_LIMIT = prevprime (LAST_PRIME * (LAST_PRIME + 1)) > right? > I thought my proposed code would allow us to exit potentially one prime earlier but if we have to add an additional check before the loop it doesn't help. > > > + ASSERT (i < NUMBER_OF_PRIMES); > > Should this be placed at the start of the loop or be? > > + ASSERT (i+1 < NUMBER_OF_PRIMES); > > The ASSERT on i make sense just before i is used by the instruction > prime+=primegap[i], i.e. at the end of the loop. Isn't it? > For some reason I was thinking ++i not i++ > > >> If writing the code is not too complex, it may be interesting to > >> test if it is worth. > > > > I'll try it out tonight > > Great! > > >> Did you try tweaking with the -p parameter? It can be useful when a > >> measure is "noisy". > > > > Nope I had not, using -p3 seems to work just as well. > > I would have used something like -p100000 or -p1000000, but if -p3 is > good for you, I'm happy :-) > > Ĝis, > m > _______________________________________________ gmp-devel mailing list gmp-devel@gmplib.org https://gmplib.org/mailman/listinfo/gmp-devel
