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Nov 11, 2021 · 第1章 MapReduce入门 1.1 MapReduce定义 Mapreduce是一个分布式运算程序的编程框架，是用户开发“基于hadoop的数据分析应用”的核心框架。 Mapreduce 核心功能是将用户编写的业务逻辑代码和自带默认组件整合成一个完整的分布式运算程序，并发运行在一个 hadoop 集群上。
A MapReduce program is composed of a map procedure, which performs filtering and sorting (such as sorting students by first name into queues, one queue for each name), and a reduce method, which performs a summary operation (such as counting the number of students in each queue, yielding name frequencies).
Oct 12, 2022 · Java的序列化是一个重量级序列化框架（Serializable），一个对象被序列化后，会附带很多额外的信息（各种校验信息，header，继承体系。. ），不便于在网络中高效传输；所以，hadoop自己开发了一套序列化机制Writable，精简，高效。. 简单代码验证两种序列化机制的 ...
MapReduce 是Google提出的一个软件架构，用于大规模数据集的并行运算。 概念“ Map （映射）”和“ Reduce （归约）”，及他们的主要思想，都是从 函数式编程语言 借鉴的，还有从 矢量编程 语言借来的特性。
MapReduce is a programming paradigm that enables massive scalability across hundreds or thousands of servers in a Hadoop cluster. As the processing component, MapReduce is the heart of Apache Hadoop. The term "MapReduce" refers to two separate and distinct tasks that Hadoop programs perform.
