internal static Func <uint, uint> GetRandomHashMethod1(uint size)
{
uint a = (uint)random.Next();
uint b = (uint)(random.Next(65536) << 16);
int shift = 31 - (int)BitHacks.Log2Ceiling(size);
return((x) => ((a * x + b) >> shift) >> 1);
}
static void Main(string[] args)
{
uint m = BitHacks.RoundToPower((uint)random.Next(1000, int.MaxValue / 2));
int width = (int)BitHacks.Log2Ceiling(m);
var fks = GetRandomHashMethodFKS(m);
var nomod1 = GetRandomHashMethod1(m);
var nomod2 = GetRandomHashMethod2(width);
var randoms = Enumerable.Range(0, 100000000).Select((i) => (uint)random.Next((int)m)).ToArray();
uint a = (uint)random.Next();
uint b = (uint)(random.Next(65536) << 16);
var watch = new Stopwatch();
watch.Start();
for (int i = 0; i < randoms.Length; i++)
{
fks(randoms[i]);
}
watch.Stop();
Console.WriteLine("fks: {0}", watch.ElapsedMilliseconds);
watch.Restart();
for (int i = 0; i < randoms.Length; i++)
{
nomod1(randoms[i]);
}
watch.Stop();
Console.WriteLine("nomod by size: {0}", watch.ElapsedMilliseconds);
watch.Restart();
for (int i = 0; i < randoms.Length; i++)
{
nomod2(randoms[i]);
}
watch.Stop();
Console.WriteLine("nomod by width: {0}", watch.ElapsedMilliseconds);
watch.Restart();
for (int i = 0; i < randoms.Length; i++)
{
UnrolledHash1(a, b, width, randoms[i]);
}
watch.Stop();
Console.WriteLine("unrolled conditional: {0}", watch.ElapsedMilliseconds);
watch.Restart();
for (int i = 0; i < randoms.Length; i++)
{
UnrolledHash2(a, b, width, randoms[i]);
}
watch.Stop();
Console.WriteLine("unrolled shift by width: {0}", watch.ElapsedMilliseconds);
watch.Restart();
for (int i = 0; i < randoms.Length; i++)
{
UnrolledHash3(a, b, m, randoms[i]);
}
watch.Stop();
Console.WriteLine("unrolled shift by size: {0}", watch.ElapsedMilliseconds);
}
internal static uint UnrolledHash3(uint a, uint b, uint size, uint x)
{
return(((a * x + b) >> (31 - (int)BitHacks.Log2Ceiling(size))) >> 1);
}