main.cpp

00001 //
00002 // Title        : Sieve of Eratosthenes
00003 // Author       : Claus Kuehnel
00004 // Date         : 2016-02-16
00005 // Id           : sieve_ARCH_PRO
00006 // based on     : sieve.pde from 2010
00007 //
00008 // DISCLAIMER:
00009 // The author is in no way responsible for any problems or damage caused by
00010 // using this code. Use at your own risk.
00011 //
00012 // LICENSE:
00013 // This code is distributed under the GNU Public License
00014 // which can be found at http://www.gnu.org/licenses/gpl.txt
00015 //
00016 
00017 #include "mbed.h"
00018 
00019 #define TRUE 1
00020 #define FALSE 0
00021 
00022 int i,k, prime,count;
00023 
00024 const int SIZE = 1000;    
00025 char flags[SIZE+1];
00026 
00027 Serial pc(USBTX, USBRX);
00028 Timer timer;
00029 
00030 DigitalOut myled(LED1);
00031 
00032 int main() 
00033 {
00034   myled = 0;
00035   pc.baud(115200);
00036   pc.printf("Sieve of Eratosthenes - Arch Pro\n");
00037   
00038   /*-------------------------------------------------------------------
00039   The following code is an implementation of the Sieve of Eratosthenes.
00040   -------------------------------------------------------------------*/
00041   pc.printf("5000 iterations\n");
00042   timer.start();
00043   unsigned long time = timer.read_ms();
00044   for (unsigned int iter = 1; iter <= 5000; iter++)     /* do program 5000 times */
00045   { 
00046     count = 0;                       /* initialize prime counter */
00047     for (i = 0; i <= SIZE; i++)      /* set all flags true */
00048       flags[i] = TRUE;
00049     for (i = 0; i <= SIZE; i++)
00050     {
00051       if (flags[i])                  /* found a prime */
00052       {
00053     prime = i + i + 3;               /* twice index + 3 */
00054     for (k = i + prime; k <= SIZE; k += prime)
00055       flags[k] = FALSE;              /* kill all multiples */
00056     count++;                         /* primes found */
00057       }
00058     }
00059   }
00060   myled = 1;
00061   time = timer.read_ms() - time;
00062   pc.printf("%d primes.\n", count);        
00063   pc.printf("Runtime = %d ms\n",time);
00064 }