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prime_cpu_mt.c
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prime_cpu_mt.c
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#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <sys/time.h>
/* usage statement */
void usage()
{
printf("Usage: prime_cpu_mt N\n");
exit(0);
}
/* returns 0 if N is prime */
static inline int is_prime(int N)
{
int i;
int max;
max = sqrt(N);
if(N < 2) return -1;
/* check if N is divisable by any number up to sqrt(N) */
for(i = 2; i <= max; i++)
{
if(N % i == 0)
return -1;
}
return 0;
}
/* returns a summation of every prime number up to N */
long long sum_primes(int N)
{
int i;
long long sum = 0;
/* OpenMP parallel reduction over this for loop - easy multithreaded parallelism */
#pragma omp parallel for reduction(+:sum)
for(i = 0; i < N; i++)
{
if(is_prime(i) == 0)
{
sum += i;
}
}
return sum;
}
int main(int argc, char **argv)
{
int N;
long long sum;
double t0, t1;
struct timeval tv;
if(argc != 2)
usage();
N = atoi(argv[1]);
/* get a start time before the sum_primes call */
gettimeofday(&tv, NULL);
t0 = tv.tv_usec;
t0 /= 1000000.0;
t0 += tv.tv_sec;
sum = sum_primes(N);
/* get an ending time after sum_primes returns */
gettimeofday(&tv, NULL);
t1 = tv.tv_usec;
t1 /= 1000000.0;
t1 += tv.tv_sec;
printf("Prime CPU MT\n");
printf("N: %d\n", N);
printf("sum of primes up to N: %lld\n", sum);
printf("Time elapsed: %lf\n\n", t1 - t0);
return 0;
}