Monday, August 28, 2023

Digest for comp.lang.c++@googlegroups.com - 13 updates in 2 topics

Ben Bacarisse <ben.usenet@bsb.me.uk>: Aug 28 12:49AM +0100

>> tests. Shouldn't take too long.
 
> Took 14 minutes to find those 203280221 primes single threaded
> on i7-8550U.
 
What do you mean by find? Do you include printing them out because that
will depend rather more on the OS.
 
I wanted to try a newer algorithm, so I coded up a rather naive version
of Atkin & Bernstein's sieve in C. It needs some tidying and I imagine
a bit can be shaved off the time.
 
It can generate a bitmap of the 203280221 primes and then count them in
about 40 seconds on an i5-8265U CPU @ 1.60GHz (single threaded). It
takes about 55 seconds to write them (in decimal) to a file. The result
is over 2GB:
 
$ wc primes
203280221 203280221 2178719347 primes
 
--
Ben.
Bonita Montero <Bonita.Montero@gmail.com>: Aug 28 06:15AM +0200

I optimized the code somewhat further:
 
#include <iostream>
#include <vector>
#include <charconv>
#include <string_view>
#include <algorithm>
#include <fstream>
#include <cctype>
#include <cstring>
#include <bit>
#include "ndi.h"
 
#if defined(_MSC_VER)
#pragma warning(disable: 26495) // uninitialized member
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