public void test_remove_random_bit_vs_hashset_performance()
{
HashSet <int> hashSet = new HashSet <int> {
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
11, 12, 13, 14, 15, 16, 17, 18, 19, 20,
21, 22, 23, 24, 25, 26, 27, 28, 29, 30
};
int bitmask = 2147483647;
Stopwatch stopWatch = new Stopwatch();
int[] selection0 = new int[31];
int[] selection1 = new int[31];
// ---
UnityEngine.Random.seed = 0;
int c = 0;
stopWatch.Start();
while (bitmask != 0)
{
selection0[c++] = BitOpsHelper.RemoveRandomBit(ref bitmask);
}
stopWatch.Stop();
var t0 = stopWatch.ElapsedTicks;
UnityEngine.Random.seed = 0;
c = 0;
stopWatch.Start();
while (hashSet.Count > 0)
{
int i = UnityEngine.Random.Range(0, hashSet.Count);
var e = hashSet.GetEnumerator();
while (i-- >= 0)
{
e.MoveNext();
}
hashSet.Remove(selection1[c++] = e.Current);
}
stopWatch.Stop();
var t1 = stopWatch.ElapsedTicks;
// ---
//UnityEngine.Debug.Log("t0: " + t0);
//UnityEngine.Debug.Log("t1: " + t1);
//string str0 = "", str1 = "";
//for (int i = 0; i < 31; i++)
//{
// str0 += selection0[i] + ", ";
// str1 += selection1[i] + ", ";
//}
//UnityEngine.Debug.Log("selection0: " + str0);
//UnityEngine.Debug.Log("selection1: " + str1);
Assert.AreIdenticalSets(selection0, selection1, (a, b) => a == b);
Assert.IsTrue(t0 < t1);
}
public static int RemoveRandomBit(ref int bitmask)
{
var randomBitIndex = UnityEngine.Random.Range(0, PopCount(bitmask));
var actualBitIndex = BitOpsHelper.BFind(bitmask, randomBitIndex + 1);
bitmask &= ~(1 << actualBitIndex);
return(actualBitIndex);
}
public void test_bfind()
{
// 11 = 1011, so the third flipped bit is in index 3
Assert.AreEqual(3, BitOpsHelper.BFind(11, 3));
// 3 = 11, so there's no third flipped bit and BFind returns 32
Assert.AreEqual(32, BitOpsHelper.BFind(3, 3));
// searching for the 0th flipped bit always causes BFind to return 32
Assert.AreEqual(32, BitOpsHelper.BFind(1, 0));
}