为什么处理排序数组比处理未排序数组慢？

我有一个包含 500000 个随机生成的 Tuple<long,long,string> 对象的列表，我正在对这些对象执行简单的“介于”搜索：

var data = new List<Tuple<long,long,string>>(500000);
...
var cnt = data.Count(t => t.Item1 <= x && t.Item2 >= x);

当我生成随机数组并搜索 100 个随机生成的 x 值时，搜索在大约四秒内完成。然而，知道了 great wonders that sorting does to searching，我决定在运行 100 次搜索之前对我的数据进行排序 - 首先按 Item1，然后按 Item2，最后按 Item3。由于分支预测，我希望排序后的版本执行得更快一些：我的想法是，一旦我们到达 Item1 == x 的点，所有对 t.Item1 <= x 的进一步检查都会正确地预测分支为“不接受”，加速搜索的尾部。令我惊讶的是，排序数组的搜索时间是原来的两倍！

我尝试改变运行实验的顺序，并为随机数生成器使用不同的种子，但效果是一样的：在未排序数组中的搜索运行速度几乎是在同一数组中搜索的两倍，但是排序！

有人对这种奇怪的效果有很好的解释吗？我的测试源代码如下；我正在使用 .NET 4.0。

private const int TotalCount = 500000;
private const int TotalQueries = 100;
private static long NextLong(Random r) {
    var data = new byte[8];
    r.NextBytes(data);
    return BitConverter.ToInt64(data, 0);
}
private class TupleComparer : IComparer<Tuple<long,long,string>> {
    public int Compare(Tuple<long,long,string> x, Tuple<long,long,string> y) {
        var res = x.Item1.CompareTo(y.Item1);
        if (res != 0) return res;
        res = x.Item2.CompareTo(y.Item2);
        return (res != 0) ? res : String.CompareOrdinal(x.Item3, y.Item3);
    }
}
static void Test(bool doSort) {
    var data = new List<Tuple<long,long,string>>(TotalCount);
    var random = new Random(1000000007);
    var sw = new Stopwatch();
    sw.Start();
    for (var i = 0 ; i != TotalCount ; i++) {
        var a = NextLong(random);
        var b = NextLong(random);
        if (a > b) {
            var tmp = a;
            a = b;
            b = tmp;
        }
        var s = string.Format("{0}-{1}", a, b);
        data.Add(Tuple.Create(a, b, s));
    }
    sw.Stop();
    if (doSort) {
        data.Sort(new TupleComparer());
    }
    Console.WriteLine("Populated in {0}", sw.Elapsed);
    sw.Reset();
    var total = 0L;
    sw.Start();
    for (var i = 0 ; i != TotalQueries ; i++) {
        var x = NextLong(random);
        var cnt = data.Count(t => t.Item1 <= x && t.Item2 >= x);
        total += cnt;
    }
    sw.Stop();
    Console.WriteLine("Found {0} matches in {1} ({2})", total, sw.Elapsed, doSort ? "Sorted" : "Unsorted");
}
static void Main() {
    Test(false);
    Test(true);
    Test(false);
    Test(true);
}

Populated in 00:00:01.3176257
Found 15614281 matches in 00:00:04.2463478 (Unsorted)
Populated in 00:00:01.3345087
Found 15614281 matches in 00:00:08.5393730 (Sorted)
Populated in 00:00:01.3665681
Found 15614281 matches in 00:00:04.1796578 (Unsorted)
Populated in 00:00:01.3326378
Found 15614281 matches in 00:00:08.6027886 (Sorted)