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MySQL和MongoDB设计实例进行对比 - 大数据 & AI - 清泛网 - 专注C/C++及内核技术
...查询：
db.getCollection("mobiles").find({
"params": {
$all: [
{$elemMatch: {"name": "待机时间", "value": {$gt: 100}}},
{$elemMatch: {"name": "外观设计", "value": "直板"}}
]
}
});
注：查询中用到的$all，$elemMatch等高...
LINGO使用指南 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...集。
例2.3
sets:
product/A B/;
machine/M N/;
week/1..2/;
allowed(product,machine,week):x;
endsets
LINGO生成了三个父集的所有组合共八组作为allowed集的成员。列表如下：
编号 成员
1 (A,M,1)
2 2 (A,M,2...
闲扯Nginx的accept_mutex配置 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...际上Nginx作者Igor Sysoev曾经给过相关的解释：
OS may wake all processes waiting on accept() and select(), this is called thundering herd problem. This is a problem if you have a lot of workers as in Apache (hundreds and more), but this insensible if you have just several workers as ...
使用App Inventor 2 控制物联网设备/低功耗蓝牙设备(BLE) · App Inventor 2 中文网
...hyay, D., & Sen, J. (2011). Internet of things: Applications and challenges in technology and standardization. Wireless Personal Communications, 58(1), 4969.
[2] Wolber, D., Abelson, H., Spertus, E., & Looney, L. (2011). App Inventor. ” O’Reilly Media, Inc.”.
[3] Macke...
了解 Boost Filesystem Library - C/C++ - 清泛网 - 专注C/C++及内核技术
...即使其他程序在访问同一文件也如此！
unsigned long remove_all(const path& p)：此 API 尝试删除路径 p 所引用的文件或目录。与 remove 不同，此函数并不会特殊考虑不为空的目录。此函数是 UNIX rm –rf 命令的 Boost 对等项。
实用工具...
App Inventor 2 DynamicComponents 拓展：动态创建AI2组件对象 · App Inventor 2 中文网
...t.
When replacing an ID, it will loop through ALL IDs and replace each one that contains the old ID! Even if the ID you're wanting to replace is "Timmy", but there are IDs like "Timmy-truck". To be clear again, only "Timmy" from "Timmy-truck" will be replaced, the "-truc...
如何获取IE (控件)的所有链接（包括Frameset, iframe） - C/C++ - 清泛网 -...
...（包括Frameset, iframe）IE 顶层 body 节点通过IHTMLElement->get_all 方法无法获取iframe 里面的节点列表：CComPtr<IHTMLElement> body;...CComPtr<IDispatc...IE 顶层 body 节点通过IHTMLElement->get_all 方法无法获取iframe 里面的节点列表：
CComPtr<IHTMLElement> b...
自动生成Linux下Makefile全攻略（automake原理） - C/C++ - 清泛网 - 专注C/C++及内核技术
...configure 输出Makefile文件
2、make 输出二进制
3、make install 安装二进制到指定目录
make及make install的规则都需要参照Makefile文件，而Makefile是自动生成的，大家有兴趣可以查看下Makefile，代码很长很复杂。当然我们可以直接在Mak...
如何选择机器学习算法 - 大数据 & AI - 清泛网 - 专注IT技能提升
...g algorithm to choose for your classification problem? Of course, if you really care about accuracy, your best bet is to test out a couple different ones (making sure to try different parameters within each algorithm as well), and select the best one by cross-validation. But if you’re simply l...
如何选择机器学习算法 - 大数据 & AI - 清泛网 - 专注IT技能提升
...g algorithm to choose for your classification problem? Of course, if you really care about accuracy, your best bet is to test out a couple different ones (making sure to try different parameters within each algorithm as well), and select the best one by cross-validation. But if you’re simply l...