值类型和引用类型在hashtable里面性能比较分析1 -GetHashCode()
上篇文章中,测试了一下值类型数据和引用类型数据在hashtable中插入和读取的性能,测试结果和本人预期也有一些出入,msdn有一篇文章介绍在box,unbox的时候,性能关系为:class>interface>int,原文:Open the Box! Quick,进一步分析了上篇测试,发现其实影响测试性能还有其它几个方面的因素,本篇就针对不同数据类型在GetHashCode()上面的消耗
测试程序如下;
结果表,我暂且不画在这上面了,因为比较多,而且不好排版,我只说一下结果,int类型的数据比字符串类型的在GetHashCode()的效率上要高50多倍,比Class的也高50-70倍
察看了GetHashCode()的实现
Int32
而object的实现方法,我 不太理解:
测试程序如下;
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System.Diagnostics.Stopwatch stopWatch = new System.Diagnostics.Stopwatch();
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stopWatch.Start();
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for (int i = 0; i < CompareCount; i++)
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{
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int hashCode = i.GetHashCode();
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}
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stopWatch.Stop();
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System.Diagnostics.Stopwatch stopWatch2 = new System.Diagnostics.Stopwatch();
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stopWatch2.Start();
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for (int i = 0; i < CompareCount; i++)
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{
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int hashCode = i.ToString().GetHashCode();
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}
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stopWatch2.Stop();
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System.Diagnostics.Stopwatch stopWatch3 = new System.Diagnostics.Stopwatch();
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stopWatch3.Start();
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for (int i = 0; i < CompareCount; i++)
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{
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int hashCode = new Test().GetHashCode();
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}
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stopWatch3.Stop();
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long t1 = stopWatch.ElapsedTicks;
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long t2 = stopWatch2.ElapsedTicks;
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long t3 = stopWatch3.ElapsedTicks;
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Console.WriteLine(t1.ToString());
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Console.WriteLine(t2.ToString());
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Console.WriteLine(t3.ToString());
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Console.WriteLine((double)(t2/t1));
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ArrayList list = new ArrayList();
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}
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结果表,我暂且不画在这上面了,因为比较多,而且不好排版,我只说一下结果,int类型的数据比字符串类型的在GetHashCode()的效率上要高50多倍,比Class的也高50-70倍
察看了GetHashCode()的实现
Int32
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public override int GetHashCode()
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{
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return this;
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}
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String
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[ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)]
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public override unsafe int GetHashCode()
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{
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fixed (char* text1 = ((char*) this))
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{
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char* chPtr1 = text1;
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int num1 = 0x15051505;
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int num2 = num1;
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int* numPtr1 = (int*) chPtr1;
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for (int num3 = this.Length; num3 > 0; num3 -= 4)
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{
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num1 = (((num1 << 5) + num1) + (num1 >> 0x1b)) ^ numPtr1[0];
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if (num3 <= 2)
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{
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break;
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}
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num2 = (((num2 << 5) + num2) + (num2 >> 0x1b)) ^ numPtr1[1];
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numPtr1 += 2;
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}
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return (num1 + (num2 * 0x5d588b65));
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}
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}
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而object的实现方法,我 不太理解:
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public virtual int GetHashCode()
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{
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return object.InternalGetHashCode(this);
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}
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[MethodImpl(MethodImplOptions.InternalCall)]
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internal static extern int InternalGetHashCode(object obj);
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object的具体处理方法
而从int,string类型算法可以轻易看出效率差别,虽然string类型还有unsafe .
而且,值类型必须重写GetHashCode。
从这里可以看出,在上次测试中,GetHashCode帮了int类型不少忙呀!
作者:jillzhang
出处:http://jillzhang.cnblogs.com/
本文版权归作者和博客园共有,欢迎转载,但未经作者同意必须保留此段声明,且在文章页面明显位置给出原文连接,否则保留追究法律责任的权利。
出处:http://jillzhang.cnblogs.com/
本文版权归作者和博客园共有,欢迎转载,但未经作者同意必须保留此段声明,且在文章页面明显位置给出原文连接,否则保留追究法律责任的权利。