List的Capacity
Capacity
在.NET中List的容量应该只是受到硬件限制。
属性Capacity的真正含义，是创建List时给它预分配的容量。
一旦项的数量超过了当前的Capacity，Capacity会以
Capacity = (Capacity==0)?A_VALUE_YOU_CANNOT_SURE:(Capacity*2)
的方式增长。
当使用默认构造函数创建一个List时，Capacity就是0。（或者你非要用一个0作为capacity参数调用构造）
所以当Capacity是0时，我们为List添加了第一个项目后，Capacity是多少呢？
对，是A_VALUE_YOU_CANNOT_SURE。
不过，在.NET2.0和.NET4.5中，这个值看上去都是4。
System.Diagnostics.Debug.WriteLine(string.Format("default capacity is : {0}", new List<string>().Capacity));
int initCapacity = ;
List<string> l = new List<string>(initCapacity);
System.Diagnostics.Debug.WriteLine(string.Format("constructe a list with capacity: {0}", l.Capacity));
for (int u = ; u < ; ++u)
{
System.Diagnostics.Debug.WriteLine(string.Format("Count: {0}, Capacity: {1}", l.Count, l.Capacity));
//l.TrimExcess();
//System.Diagnostics.Debug.WriteLine(string.Format(" TrimExcess() -> Count: {0}, Capacity: {1}", l.Count, l.Capacity));
l.Add("");
}
输出
default capacity is :
constructe a list with capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
TrimExcess()
TrimExcess()的意思就是，如果Capacity大于Count，清掉哪些没有使用的空间。基本上可以理解成让Capacity等于Count，只是基本上，不能信赖这一点。.NET毕竟还要考虑很多性能问题。TrimExcess method does nothing if the list is at more than 90 percent of capacity——这就是.NET的方式。实际上把上面那段代码中的注释放开，就会看到确实存在Capacity和Count不等的情况（然而，并不是90%哟）。Capacity不够以后的增长规则，仍然是*2，并不会因为被Trim过就只是加1。
放开注释后的输出
default capacity is :
constructe a list with capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
发现并不是90%以后
System.Diagnostics.Debug.WriteLine(string.Format("default capacity is : {0}", new List<string>().Capacity));
int initCapacity = ;
List<string> l = new List<string>(initCapacity);
System.Diagnostics.Debug.WriteLine(string.Format("constructe a list with capacity: {0}", l.Capacity));
int initCount = ;
for (int u = ; u < initCount; ++u)
{
l.Add(u.ToString());
}
for (int u = ; u < initCount; ++u)
{
System.Diagnostics.Debug.WriteLine(string.Format("Count: {0}, Capacity: {1}", l.Count, l.Capacity));
l.TrimExcess();
System.Diagnostics.Debug.WriteLine(string.Format(" TrimExcess() -> Count: {0}, Capacity: {1}", l.Count, l.Capacity));
l.Remove(u.ToString());
}
得到
default capacity is :
constructe a list with capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
貌似条件是酱紫的
if( count<(int)Math.Floor((double)capacity*0.9) )
do trim
我也不知道我要干嘛
List的Capacity的更多相关文章
- 大数据之Yarn——Capacity调度器概念以及配置
试想一下,你现在所在的公司有一个hadoop的集群.但是A项目组经常做一些定时的BI报表,B项目组则经常使用一些软件做一些临时需求.那么他们肯定会遇到同时提交任务的场景,这个时候到底如何分配资源满足这 ...
- Hadoop Capacity Scheduler源码实现剖析
作者: 大圆那些事 | 文章可以转载,请以超链接形式标明文章原始出处和作者信息 网址: http://www.cnblogs.com/panfeng412/archive/2013/09/13/had ...
- Sizing and Capacity Planning for SharePoint 2013 - Resources
http://blogs.msdn.com/b/sanjaynarang/archive/2013/04/06/sizing-and-capacity-planning-for-sharepoint- ...
- 用了skin皮肤控件之后，报错:容量超出了最大容量 参数名:capacity
http://blog.csdn.net/keenweiwei/article/details/7403869 用了皮肤控件之后,报错:容量超出了最大容量 参数名:capacity MessageBo ...
- Capacity Scheduler 队列设置
先附一个官网地址 Capacity Scheduler是YARN中默认的资源调度器. 相关参数配置: 资源分配相关参数 ``` (1) capacity:队列的资源容量(百分比). 当系统非常繁忙时, ...
- STL:string 大小（Size）和容量（Capacity）
strings存在三种“大小”: 1.size()和length() 返回string中现在的字符个数.上述两个函数等效. 成员函数empty()用来检验字符数是否为0,亦即字符串是否为空.你应该优先 ...
- hdu 1839 Delay Constrained Maximum Capacity Path 二分/最短路
Delay Constrained Maximum Capacity Path Time Limit: 20 Sec Memory Limit: 256 MB 题目连接 http://acm.hdu. ...
- Web Capacity Analysis Tool 压力测试工具使用笔记
一.背景介绍 Web Capacity Analysis Tool是微软轻量级Web压力测试工具, 早先是IIS 6.0Resource Tool kit 工具包中的一个组件,现在独立出来有一个社区版 ...
- max_size, capacity and size 的区别
The max_size() function returns the maximum number of elements that the container can hold. The max_ ...
随机推荐
- 一、Android屏幕的计量单位
px :是屏幕的像素点in :英寸mm:毫米pt :磅,1/72英寸dp :一个基于density的抽象单位,如果一个160dpi的屏幕,1dp=1pxdip :等同于dpsp :同dp ...
- Junity测试最大子数列和的Java程序
1.Java环境的安装与配置: Jdk的安装: Jdk下载链接:http://www.oracle.com/technetwork/java/javase/downloads/index-jsp-13 ...
- JAVA 语法基础综合练习——学生成绩管理系统
代码如下:package com.lovo.manager; import java.util.Scanner; /** * 学生管理 * * @author Administrator * */ p ...
- 关于python函数的学习记录
1.默认参数必须指向不变对象! 2. extra = {'city': 'Beijing', 'job': 'Engineer'}注意kw获得的dict是extra的一份拷贝,对kw的改动不会影响到函 ...
- oracle 行转列、列转行
最近做数据处理,经常遇到需要行转列.列转行的场景,记录个非常简单实用的oracle 列转行.行转的列方法 1.行转列,基础数据如下 做行转列处理 处理SQL select user_name,max ...
- cocos2dx 之 android java 与 c++ 互相调用 代码(以百度定位为例子)
在作cocosdx项目移植到android上时,预见各种头痛问题,今天首先就说说如何在 java 中调用c++ 代码. 这里就用百度定位为例吧,也是我项目中的一小块内容.首先,先百度一下 “百度定位s ...
- windows下开启mysql表名大小限制
找到my.ini文件 在文件中找到 [mysqld]的下面, 看有没有 [mysqld] lower_case_table_names 的设置, 如果没有 添加lower_case_table_nam ...
- Web Deploy安装时显示Web Management Service无法启动
在安装显示如题错误,看了日志: IISWMSVC_STARTUP_UNABLE_TO_READ_CERTIFICATE 无法读取带有指纹"3f60e39108a7e4c54f671b75 ...
- 修改hive分区表，在分区列前增加一个字段
本文主要为了测试,在有数据的分区表中增加新的一个非分区字段后,新数据加入表中是否正常. 原始数据 1;zhangsan 2;zhangsan 3;zhangsan 4;lisi 5;lisi 6;li ...
- MCMC: The Metropolis Sampler
本文主要译自 MCMC: The Metropolis Sampler 正如之前的文章讨论的,我们可以用一个马尔可夫链来对目标分布 \(p(x)\) 进行采样,通常情况下对于很多分布 \(p(x)\) ...