this algorithm has been my lit. secret... I've never been able to see
if there is another that beat it.
CPU: Intel Pentiun 4 2.26GHz
Cores: 1
RAM: 768MB
OS: Windows XP Professional SP3
.Net: 3.5
Number of primes in 10 seconds: 168876
Highest Prime found: 1078673
It's deterministic, it gets all the primes, no skips, all in order.
Note: running without looking the console to get its real speed, if
you are looking it, it falls a lot. [Hey the DateTime.Now call also
takes time!!!]
stats watching the console:
Number of primes in 10 seconds: 59082 (34% aprox)
Highest Prime found: 361219
I'm pretty sure I can optimize it, but I haven't had the need.
I'm soooo... nostalgic to give this away... ok, here I go!
using System;
using System.Diagnostics;
namespace Primes
{
class Program
{
const int seconds = 10;
[DebuggerNonUserCode()]
static bool IsPrim(double Num)
{
if (Num == 2 ||Num == 3) return true;
if (Num % 2 == 0 || Num % 3 == 0) return false;
double J, H = Math.Ceiling(Math.Sqrt(Num));
for (J = 5; J <= H; J+=6) if (Num % J == 0 || Num % J+2 == 0)
return false;
return true;
}
[DebuggerNonUserCode()]
static void Main()
{
DateTime x, y = DateTime.Now;
double a = 1, b = 0;
do
{
if (IsPrim(a))
{
Console.WriteLine(a);
b++;
}
a++;
x = DateTime.Now;
} while ((x - y).TotalSeconds < seconds);
Console.WriteLine("Done");
Console.WriteLine("{0} primes founds in {1} seconds", b,
seconds);
Console.ReadKey();
}
}
}
@Cerberus:
Sieve of Eratosthenes isn't appropiate for this, sorry.
