time measurement for rand/random/arc4random.

time_random.m

//
//  main.m
//  CodeTest
//
//  Created by [email protected] on 2013/01/11.
//  Copyright (c) 2013 Eien Factory. All rights reserved.
//

#import <Foundation/Foundation.h>
#import <mach/mach_time.h>
#import <stdlib.h>

#import <ScreenSaver/ScreenSaver.h>

#define TEST 4

int main(int argc, const char * argv[])
{
    @autoreleasepool {
        uint64_t start, elapsed;
        mach_timebase_info_data_t base;
        mach_timebase_info(&base);

        unsigned int seed;
        seed = (unsigned int)time(NULL);
        srandom(seed);
        srand(seed);
        
        start = mach_absolute_time();

        for (int i=0; i<1000*1000; i++) {
            long value;
#if TEST==1
            value = arc4random();//time = 12 939 828(nsec)
#elif TEST==2
            value = random();//time = 6 012 601(nsec)
#elif TEST==3
            value = rand();//time = 6 720 593(nsec)
#elif TEST==4
            value = SSRandomIntBetween(0,100);//time = 9 549 701(nsec)
#endif
        }

        elapsed = mach_absolute_time() - start;
        uint64_t nsec = elapsed * base.numer / base.denom;
        printf("time = %lld(nsec)\n",nsec);
    }
    return 0;
}