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
- .net中使用ODP.net访问Oracle数据库（无客户端部署方法）
ODP.net是Oracle提供的数据库访问类库,其功能和效率上都有所保证,它还有一个非常方便特性:在客户端上,可以不用安装Oracle客户端,直接拷贝即可使用. 以下内容转载自:http://b ...
- MVC5 CodeFirst （一）
创建一个MVC5项目,VS生成了AccountController.HomeController,F5直接运行,实现了注册.登录.修改……但是注册的用户只是在内存里,下面我们来持久化. 三个命令:en ...
- 无法将文件" "复制到“bin\*.*”。对路径“bin\*.*”的访问被拒绝。 解决方法
如果没有特别什么代码的错误,而是更新了某个自动获取的Webserive 那么什么都不用管,直接VS关闭,从新打开就好了.
- PHPnow在win8下安装失败的解决办法
提示: 安装服务[ Apache_pn ]失败,可能原因如下:1.服务名已存在,请卸载或使用不同服务名.2.非管理员权限,不能操作Window NT服务. 解决方案: 搜索:命令提示符 , 右键以 ...
- 【转】JavaScript之web通信
原文转自:http://cloudbbs.org/forum.php?mod=viewthread&tid=28773&page=1&extra=#pid180304 一.前言 ...
- B - Dividing
Time Limit:1000MS Memory Limit:10000KB 64bit IO Format:%I64d & %I64u Submit Status Descr ...
- git学习：关于origin和master
[转载请注明出处]http://www.cnblogs.com/mashiqi 2016/10/27 本文主要是对这篇博客文章的理解. git的服务器端(remote)端包含多个repository, ...
- 使用 itext、flying-saucer 实现html转PDF（转）
转自 http://blog.csdn.net/mhouwei62/article/details/51394804 表示感谢 itext-2.1.7高于此版本已经更新为AGPL授权,不建议使用. 添 ...
- Python 程序员经常犯的 10 个错误
关于PythonPython是一种解释性.面向对象并具有动态语义的高级程序语言.它内建了高级的数据结构,结合了动态类型和动态绑定的优点,这使得... 关于Python Python是一种解释性.面向对 ...
- js获取url的常用方法
//设置或获取对象指定的文件名或路径. console.log(window.location.pathname) //设置或获取整个 URL 为字符串. console.log(window.loc ...