rand64

#include "stdlib.h"
#include "stdint.h"
 
uint64_t rand64()
{
	// Combin 4 parts of low 16-bit of each rand()
	uint64_t R0 = (uint64_t)random() << 48;
	uint64_t R1 = (uint64_t)random() << 48 >> 16;
	uint64_t R2 = (uint64_t)random() << 48 >> 32;
	uint64_t R3 = (uint64_t)random() << 48 >> 48;
	return R0 | R1 | R2 | R3;
}
 
#define SEGS 100
#define TIMES 50000
 
// Show segments
int main (int argc, char const *argv[])
{
	const uint64_t SEG = UINT64_MAX / SEGS;
	int f[SEGS] = { 0 };
	for(int i = 0; i < TIMES; ++i)
	{
		uint64_t r = rand64();
		f[r / SEG]++;
	}
	for (int i = 0; i < SEGS; ++i)
	{
		printf("#%2d: (%20llu ~ %20llu) %dn", i, i * SEG, (i + 1) * SEG - 1, f[i]);
	}
	return 0;
}