April 2014
Beginner to intermediate
830 pages
15h 21m
Chinese
Content preview from Mathematica 錦囊妙計
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16.13 以 Map-Reduce 技巧處理大量檔案
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669
討論說明
如果你想練習本文所述的
map-reduce
架構範例，請使用
Dictionary.m
與
MapReduce.m
套件，這些套件的程式碼內容以解說為主，請於範例中載
入 這 些 套 件， 並 記 得 使 用
DistributeDefinitions
指 令 於 遠 端 核 心 建 立
map
、
reduce
與
parse
等函數。[Page-673]
mapReduce.nb
檔案中提供一些使用範例。
如果你沒有
map-reduce
程式架構的設計經驗，在動手做之前最好先參考「延伸資訊」所
列的資訊，由 Google 研究員所撰寫的原創論文提供了快速入門的概述，並舉出比字數
計算更進階的應用。關於
map-reduce
架構，首先應了解的是，它只有在須處理的檔案數
量及平行運算核心數量都很大的情況下才是一個有效率的方法。須處理的資料量遠高於
單一計算核心所能提供的記憶體，是使用此架構的最佳情況，此時須分配至許多遠端核
心進行處理。為了證明這一點，以下考慮須進行字數計算的檔案數量不多的情況。
ch16.indd 669 2014/4/2 下午 04:11:18
670
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第十六章
map-reduce
架構的實作比其他平行處理的方式稍微複雜，實作上的低階
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.