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摘要:Let’s see how MapReduce reads input data and writes output data and focus on thefile formats it uses. To enable easy distributed processing, MapReduce makes certainassumptions about the data it’s processing. It also provides flexibility in dealing with avariety of data formats.Input data usually res 阅读全文

posted @ 2011-12-17 02:38 陈力 阅读(287) 评论(0) 推荐(0) 编辑

摘要:In many situations with MapReduce applications, we may wish to perform a “localreduce ” before we distribute the mapper results. Consider the WordCount example ofThe MapReduce data flow, with an emphasis on partitioning andshuffling. Each icon is a key/value pair. The shapes represents keys, whereas 阅读全文

posted @ 2011-12-17 02:35 陈力 阅读(237) 评论(0) 推荐(0) 编辑

摘要:Partitioner— redirecting output from MapperA common misconception for first-time MapReduce programmers is to use only asingle reducer大部分的一种错误的概念是程序只用一个单一的reducerAfter all, a single reducer sorts all of your data before processing—and who doesn’t like sorted data? Our discussions regarding MapReduce 阅读全文

posted @ 2011-12-17 02:28 陈力 阅读(307) 评论(0) 推荐(0) 编辑

摘要:When the reducer task receives the output from the various mappers, it sorts theincoming data on the key of the (key/value) pair and groups together all values ofthe same key.当reducer task接受到从不同r的mappers接受到输出时,他进行排序,并且进行累加。Table 3.3 Some useful Reducer implementations predefined by HadoopClass Descr 阅读全文

posted @ 2011-12-17 02:06 陈力 阅读(217) 评论(0) 推荐(0) 编辑

摘要:The function generates a (possibly empty) list of (K2, V2) pairs for a given (K1, V1)input pair. The OutputCollector receives the output of the mapping process, andthe Reporter provides the option to record extra information about the mapper asthe task progresses.Hadoop provides a few useful mapper 阅读全文

posted @ 2011-12-17 01:57 陈力 阅读(154) 评论(0) 推荐(0) 编辑

摘要:Despite our many discussions regarding keys and values, we have yet to mention theirtypes. The MapReduce framework won’t allow them to be any arbitrary class. For example,although we can and often do talk about certain keys and values as integers,strings, and so on, they aren’t exactly standard Java 阅读全文

posted @ 2011-12-17 01:55 陈力 阅读(181) 评论(0) 推荐(0) 编辑

摘要: 阅读全文

posted @ 2011-12-14 10:33 陈力 阅读(296) 评论(0) 推荐(0) 编辑

摘要:webbench最多可以模拟3万个并发连接去测试网站的负载能力,个人感觉要比Apache自带的ab压力测试工具好,安装使用也特别方便。 1、适用系统:Linux 2、编译安装: 引用wget http://blog.s135.com/soft/linux/webbench/webbench-1.5.tar.gztar zxvf webbench-1.5.tar.gzcd webbench-1.5make && make install 3、使用: 引用webbench -c 500 -t 30 http://127.0.0.1/test.jpg 参数说明:-c表示并发数,-t表 阅读全文

posted @ 2011-04-22 08:40 陈力 阅读(220) 评论(0) 推荐(0) 编辑

摘要:话题外内容CRT的工作原理:CRT(阴极射线管)显示器的核心部件是CRT显像管,其工作原理和我们家中电视机的显像管基本一样,我们可以把它看作是一个图像更加精细的电视机。经典的CRT显像管使用电子枪发射高速电子,经过垂直和水平的偏转线圈控制高速电子的偏转角度,最后高速电子击打屏幕上的磷光物质使其发光,通过电压来调节电子束的功率,就会在屏幕上形成明暗不同的光点形成各种图案和文字。这种技术最早是1897年由德国人布朗发明。、 一种将信号转换为图像的中间零件1、首先在服务器上安装ssh的服务器端和客户端。$ sudo apt-get install openssh-server openssh-cl. 阅读全文

posted @ 2011-04-21 13:15 陈力 阅读(704) 评论(0) 推荐(0) 编辑

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