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From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: A very slow program
Date: Wed, 02 Oct 2024 15:43:45 -0700
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Janis Papanagnou <janis_papanagnou+ng@hotmail.com> writes:
[...]
> For ordinary users it's probably sufficient to use an existing
> program; on Unix 'primes 1 1000000000' runs in about 8 seconds.
> And it's checking 2^32 numbers in 50 seconds (including 'wc'
> and creating output [suppressed by redirection]), generating
> 50847534 primes. A simple prime test of some "arbitrary large"
> number runs in no time, as does factorization of numbers with
> the Unix'es 'factor' program. Just a simple command line call.
> That existing 'primes' program also has some limit; the man page
> documents a value of 4294967295, but no error message is created
> for values up to around 1.8446744*10^19 on my system.

On my system (Ubuntu 22.04.5 LTS, 64 bits), the primes(1) man page says:

"The stop value must not be greater than 3825123056546413050."

4294967295 is of course 2**31-1.  I don't know the significance of
3825123056546413050.  The change was made by Debian, but the sources
don't explicitly give a reason.  Anyone who wants to look into it can
see the patches here:

https://salsa.debian.org/games-team/bsdgames

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */