• you are allowed to publish several entries, but please edit your post (as long as possible) to enter in your new idea. enumerate them.
  
• you are allowed to use a programming language of your desire, but keep in mind that i (or someone else) has to inspect your code and bring it to work properly, so don't use something totally unknown (i'd prefer c, c++, assembler, basic, java, even wdl if you want to try *g*)
  
• whole program or only the algorithm? if possible, the whole program.
  
• the winner is determined by the speed the algorithm has calculated the expected result, which has to be represented in memory in any form, that can - without great effort - be translated into a readable output.
  
• my computer is the reference machine, i've a pentium 4 with 1816 MHz, 512 mb DDR RAM and a GeForce 6 6600 GT GS - the rest is rather nonrelevant.
  
• measure or estimate execution time by yourself! and add your system specs to make it possible for us to sort out the entries. if your time is highly unlikely, it'll get controlled anyway, so don't cheat.

#include <iostream>
#include <cmath>
#include <bitset>

#include <windows.h>

typedef unsigned int uint;

bool check(uint n)
{
    uint lim = (uint)sqrt((double)n);

    for (uint i = 2; i <= lim; i ++)
        if (!(n%i)) return false;

    return true;
}


int _tmain(int argc, _TCHAR* argv[])
{
    std::bitset<4194304> bits;
    uint start = GetTickCount();

    std::cout << "starting..." << std::endl;

    for (uint i = 2; i <= 4194304; i ++)
        bits[i-1] = check(i);

    std::cout << "finished." << std::endl
        << (float)(GetTickCount() - start)/1000 << " seconds needed." << std::endl;

    return 0;
}

var max_loops = 11000;
var a;  //prime number
var b=2;  //counter (starting)
var c;  //division number
var d=1;  //array position
var prime_numbers[99999];  //prime number storage
var primehandle;  //filehandle
 
/*
font prime_font = "arial", 0, 16;

panel primetext 
{
	digits = 5,  5, 15, prime_font, 1, a;
	digits = 5, 25, 15, prime_font, 1, b;
	digits = 5, 45, 15, prime_font, 1, c;
	digits = 5, 65, 15, prime_font, 1, d;
	flags = visible;
}
*/
 
function main() 
{
	screen_color.blue = 200;
	prime_numbers[d]=b;  //store prime number
	b+=1;  //next number
	while(b<=pow(10,6))  //prime numbers to be checked
	{	
		c=int(b/2)+1;  //startvariable for divide the prime number
		a=b/c;  //divide the prime number
		while (frc(a)!=0&&c>2)  //check the divided number, no prime when a = integer
		{
			c-=1;  //next division number
			a=b/c;  //divide the prime number
		}
		if(c<=2){  //no valid division numbers? it's a prime number
			d+=1;  //next place in the array
			prime_numbers[d]=b;  //store the prime in the array
		}
		b+=2;  //next prime number
	}
//	while (!key_any) {wait(1);}  //wait for user input
 
//write the numbers in a text file
	primehandle = file_open_write ("primenumbers.txt");
	while (d>=0) {
		file_var_write (primehandle,prime_numbers[d]);
		file_str_write (primehandle, "\n");
		d-=1;
	}
	file_close (primehandle);
	exit;
}

var max_loops = 600000;
var a;  //prime number
var b=2;  //counter (starting)
var c;  //division number
var d=0;  //array position
var prime_numbers[83000];  //prime number storage
var primehandle;  //filehandle
var time_needed = 0;
 
/*
font prime_font = "arial", 0, 16;

panel primetext 
{
	digits = 5,  5, 15, prime_font, 1, a;
	digits = 5, 25, 15, prime_font, 1, b;
	digits = 5, 45, 15, prime_font, 1, c;
	digits = 5, 65, 15, prime_font, 1, d;
        digits = 5, 85, 15, prime_font, 1, time_needed;
	flags = visible;
}
*/
 
function main() 
{
	screen_color.blue = 200;

	prime_numbers[d]=b;  //store prime number
	b+=1;  //next number
	while(b<=1048576)  //prime numbers to be checked
	{
                timer();
	
		c=int(b/2)+1;  //startvariable for divide the prime number
		a=b/c;  //divide the prime number
		while (frc(a)!=0&&c>2)  //check the divided number, no prime when a = integer
		{
			c-=1;  //next division number
			a=b/c;  //divide the prime number
		}
		if(c<=2){  //no valid division numbers? it's a prime number
			d+=1;  //next place in the array
			prime_numbers[d]=b;  //store the prime in the array
		}
		b+=2;  //next prime number
                time_needed += timer();
                wait(1);
	}
//	while (!key_any) {wait(1);}  //wait for user input
 
//write the numbers in a text file
	primehandle = file_open_write ("primenumbers.txt");
	while (d>=0) {
		file_var_write (primehandle,prime_numbers[d]);
		file_str_write (primehandle, "\n");
		d-=1;
	}
	file_close (primehandle);
	exit;
}

Quote:

---

lol... you won

maybe i shouldn't hold contests, seems as if my ideas don't get across...

---

On the contrary, I think your contest's idea is good, a programming challenge, eventhough it might have one flaw and that is this contest is supposed to be about which algorithm works fastest. My code would probably have been very similar to that of Jostie. So I wonder if there would be a remarkable or even noticable difference in speed. Anyways, I think we are up for the next task.

Cheers