April 2014
Beginner to intermediate
830 pages
15h 21m
Chinese
Content preview from Mathematica 錦囊妙計
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16.10 運算核心間共享資料
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659
16.10 運算核心間共享資料
問題點
你的平行運算實作需要在各運算核心之間經由共享變數互相溝通。
解決方案
Mathematica 提供
SetSharedVariable
指令可在各運算核心之間同步變數定義；同樣地，
SetSharedFunction
指令則可同步符號的 downvalue。以下範例中，
list
變數是各運算
核心共享的，且每一核心都可以加入其
$KernelID
值。
討論說明
假設你正在解組合最佳化的問題，如旅行推銷員問題（traveling salesperson problem，
TSP），可能會希望每個核心都可知道目前最佳解，以避免重複計算。以下是 TSP 問題
的一種解法，使用的是模擬退火演算法。[Page-663]
16.11 於多核心運行時避免競態條件
（Race Condition）
問題點
在 Mathematica 第 7 版之前，使用者不必擔心競態條件等問題，因為所有的處理程序都
在單一執行緒下進行；在進入平行處理的領域後，由於各核心均會存取共享檔案及變
數，而導致某些微妙錯誤可能出現，除非經過特別處理，否則共享資源的同步性容易發
生問題。
ch16.indd 659 2014/4/2 下午 04:11:10
660
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第十六章
解
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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.