Confirm randomness for random function by sigma.

random_sigma.m

//
//  main.m
//  CodeTest
//
//  Created by eien.support@gmail.com on 2013/01/13.
//  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 REMAINDER
#define RANGE_MAX   (10)
#define REPEAT      (1000*1000)

typedef long (^funcBlock)(void);

double doIt(funcBlock func) {
    uint32_t count[RANGE_MAX] = {0};
    const double mean = REPEAT / RANGE_MAX;
    double sum = 0;
    
    for (int i=0; i<REPEAT; i++) {
        long value;
        value = func();
#ifdef REMAINDER
        value = value % 10;
#endif
        count[value]++;
    }
    
    for (int i = 0; i < RANGE_MAX; i++) {
//        printf("[%d] %d\n",i,count[i]);
        sum += pow((count[i] - mean),2);
    }
//    printf("%f\n", sqrt(sum/RANGE_MAX));
    return sqrt(sum/RANGE_MAX);
}

void doTest(const char *name, funcBlock func)
{
    double result = 0.0;
    int repeat = 10;
    
    for (int i=0; i<repeat; i++) {
        result += doIt(func);
    }
    
    printf("%s\t%f\n",name, result/repeat);
    
}

int main(int argc, const char * argv[])
{
    @autoreleasepool {
        unsigned int seed;
        seed = (unsigned int)time(NULL);
        srandom(seed);
        srand(seed);
        
        doTest("arc4random()", ^long(){
            long value;
            value = arc4random();
#ifndef REMAINDER
            value = ((double)value/UINT32_MAX)*(double)RANGE_MAX;
#endif
            return value;
        });
        doTest("random()", ^long(){
            long value;
            value = random();
#ifndef REMAINDER
            value = ((double)value/RAND_MAX)*(double)RANGE_MAX;
#endif
            return value;
        });
        doTest("rand()", ^long(){
            long value;
            value = rand();
#ifndef REMAINDER
            value = ((double)value/RAND_MAX)*(double)RANGE_MAX;
#endif
            return value;
        });
        doTest("SSRandomIntBetween()", ^long(){
            long value;
            value = SSRandomIntBetween(0,RANGE_MAX-1);
            return value;
        });
    
    }
    return 0;
}