Hashtable和Directory性能比较

Hashtable和Directory性能比较

在.net1.1里经常会使用到Hashtable,到里.net 2.0以后我发现有了一个很好用的IDirectory<TKey,TValue>实现类 Directory<TKey,TValue>。但还是会担心Directory<TKey,TValue>的检索效率是否跟 Hashtable相当，

据我了解ArrayList的检索效率是非常差的，BinarySearch也不如Hashtable.所以做了一个测试。

class Program
{
    static void Main(string[] args)
    {
        IntTest();

        StringTest();

        IntTryGetValueTest();

        Console.WriteLine("=========");

        IntTest();

        StringTest();

        IntTryGetValueTest();

        Console.ReadLine();
    }

    static void IntTest()
    {
        IDictionary<int, int> id = new Dictionary<int, int>();

        Hashtable ht = new Hashtable();

        int count = 1000000;

        for (int i = 0; i < count; i++)
        {
            id.Add(i, i);

            ht.Add(i, i);
        }
        //////////////
        Stopwatch st = Stopwatch.StartNew();

        for (int i = 0; i < count; i++)
        {
            int str = id[i];
        }

        st.Stop();

        Console.WriteLine(string.Format("int类型，Directory:{0}", st.ElapsedMilliseconds));
        //////////////
        st = Stopwatch.StartNew();

        for (int i = 0; i < count; i++)
        {
            object obj = ht[i];
        }

        st.Stop();

        Console.WriteLine(string.Format("int类型，Hashtable:{0}", st.ElapsedMilliseconds));
    }

    static void StringTest()
    {
        IDictionary<string, string> id = new Dictionary<string, string>();

        Hashtable ht = new Hashtable();

        int count = 1000000;

        for (int i = 0; i < count; i++)
        {
            string str = i.ToString();

            id.Add(str, str);

            ht.Add(str, str);
        }
        //////////////
        Stopwatch st = Stopwatch.StartNew();

        for (int i = 0; i < count; i++)
        {
           string i2 = id[i.ToString()];
        }

        st.Stop();

        Console.WriteLine(string.Format("string类型，Directory:{0}", st.ElapsedMilliseconds));
        //////////////
        st = Stopwatch.StartNew();

        for (int i = 0; i < count; i++)
        {
            object obj = ht[i.ToString()];
        }

        st.Stop();

        Console.WriteLine(string.Format("string类型，Hashtable:{0}", st.ElapsedMilliseconds));

    }

    static void IntTryGetValueTest()
    {
        IDictionary<int, int> id = new Dictionary<int, int>();

        Hashtable ht = new Hashtable();

        int count = 1000000;

        for (int i = 0; i < count; i++)
        {
            id.Add(i, i);

            ht.Add(i, i);
        }
        //////////////
        Stopwatch st = Stopwatch.StartNew();

        for (int i = 0; i < count; i++)
        {
            int i2 = 0;

            id.TryGetValue(i, out i2);

        }

        st.Stop();

        Console.WriteLine(string.Format("IntTryGetValue，Directory:{0}", st.ElapsedMilliseconds));
        //////////////
        st = Stopwatch.StartNew();

        for (int i = 0; i < count; i++)
        {
            object obj = ht[i];
        }

        st.Stop();

        Console.WriteLine(string.Format("int类型，Hashtable:{0}", st.ElapsedMilliseconds));
    }
}

输出为：

int类型，Directory:49
int类型，Hashtable:254
string类型，Directory:1112
string类型，Hashtable:511
IntTryGetValue，Directory:50
int类型，Hashtable:251
=========
int类型，Directory:48
int类型，Hashtable:201
string类型，Directory:944
string类型，Hashtable:505
IntTryGetValue，Directory:51
int类型，Hashtable:167

~~~~~~~~~~~~~~~~~~·

从结果我们可以发现如果key是整数型Directory的效率比Hashtable快3到4倍，

如果key是字符串型，Directory的效率只有Hashtable的一半。

另外使用TryGetValue对效率没什么影响。