Question

In C# or C++ how can I implement a branch-free sort of three (integer) numbers?

Is this possible?

Answer 1

No conditionals. Only a cast to uint. Perfect solution.

int abs (int a) 
{
    int b = a;
    b = (b >> (sizeof(int)*CHAR_BIT-1) & 1);
    return 2 * b * (a) + a; 
}
int max (int a, int b) { return (a + b + abs(a - b)) / 2; }
int min (int a, int b) { return (a + b - abs(a - b)) / 2; }


void sort (int & a, int & b, int & c)
{       
   int maxnum = max(max(a,b), c);
   int minnum = min(min(a,b), c);
   int middlenum = a + b + c - maxnum - minnum;
   a = maxnum;
   b = middlenum;
   c = minnum;
}