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< div class = "book" data-level = "11.5" data-chapter-title = "剖析" data-filepath = "ch11/ch11-05.md" data-basepath = ".." data-revision = "Mon Dec 21 2015 12:51:02 GMT+0800 (中国标准时间)" >
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前言
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< b > 0.1.< / b >
Go語言起源
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< b > 0.2.< / b >
Go語言項目
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< b > 0.3.< / b >
本書的組織
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< b > 0.4.< / b >
更多的信息
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< b > 0.5.< / b >
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致謝
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< b > 1.< / b >
入門
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< b > 1.1.< / b >
Hello, World
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< b > 1.2.< / b >
命令行參數
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< b > 1.3.< / b >
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査找重複的行
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< / li >
< li class = "chapter " data-level = "1.4" data-path = "ch1/ch1-04.html" >
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< b > 1.4.< / b >
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GIF動畵
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< b > 1.5.< / b >
穫取URL
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< b > 1.6.< / b >
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併發穫取多個URL
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< b > 1.7.< / b >
Web服務
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< b > 1.8.< / b >
本章要點
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< b > 2.< / b >
程序結構
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< b > 2.1.< / b >
命名
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< b > 2.2.< / b >
聲明
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< b > 2.3.< / b >
變量
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< b > 2.4.< / b >
賦值
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< b > 2.5.< / b >
類型
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< b > 2.6.< / b >
包和文件
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< b > 2.7.< / b >
作用域
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< b > 3.< / b >
基礎數據類型
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< b > 3.1.< / b >
整型
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< b > 3.2.< / b >
浮點數
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< b > 3.3.< / b >
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複數
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< b > 3.4.< / b >
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布爾型
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< li class = "chapter " data-level = "3.5" data-path = "ch3/ch3-05.html" >
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< b > 3.5.< / b >
字符串
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< b > 3.6.< / b >
常量
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< b > 4.< / b >
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複合數據類型
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< ul class = "articles" >
< li class = "chapter " data-level = "4.1" data-path = "ch4/ch4-01.html" >
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< b > 4.1.< / b >
數組
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< b > 4.2.< / b >
切片
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< b > 4.3.< / b >
字典
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< b > 4.4.< / b >
結構體
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< b > 4.5.< / b >
JSON
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< b > 4.6.< / b >
文本和HTML模闆
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< li class = "chapter " data-level = "5" data-path = "ch5/ch5.html" >
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< b > 5.< / b >
函數
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< b > 5.1.< / b >
函數聲明
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< b > 5.2.< / b >
遞歸
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< li class = "chapter " data-level = "5.3" data-path = "ch5/ch5-03.html" >
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< b > 5.3.< / b >
多返迴值
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< li class = "chapter " data-level = "5.4" data-path = "ch5/ch5-04.html" >
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< b > 5.4.< / b >
錯誤
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< li class = "chapter " data-level = "5.5" data-path = "ch5/ch5-05.html" >
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< b > 5.5.< / b >
函數值
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< li class = "chapter " data-level = "5.6" data-path = "ch5/ch5-06.html" >
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< b > 5.6.< / b >
匿名函數
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< li class = "chapter " data-level = "5.7" data-path = "ch5/ch5-07.html" >
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< b > 5.7.< / b >
可變參數
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< b > 5.8.< / b >
Deferred函數
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< b > 5.9.< / b >
Panic異常
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< li class = "chapter " data-level = "5.10" data-path = "ch5/ch5-10.html" >
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< b > 5.10.< / b >
Recover捕穫異常
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< b > 6.< / b >
方法
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< li class = "chapter " data-level = "6.1" data-path = "ch6/ch6-01.html" >
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< b > 6.1.< / b >
方法聲明
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< li class = "chapter " data-level = "6.2" data-path = "ch6/ch6-02.html" >
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< b > 6.2.< / b >
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基於指針對象的方法
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< li class = "chapter " data-level = "6.3" data-path = "ch6/ch6-03.html" >
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< b > 6.3.< / b >
通過嵌入結構體來擴展類型
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< li class = "chapter " data-level = "6.4" data-path = "ch6/ch6-04.html" >
< a href = "../ch6/ch6-04.html" >
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< b > 6.4.< / b >
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方法值和方法表達式
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< / li >
< li class = "chapter " data-level = "6.5" data-path = "ch6/ch6-05.html" >
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< b > 6.5.< / b >
示例: Bit數組
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< li class = "chapter " data-level = "6.6" data-path = "ch6/ch6-06.html" >
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< b > 6.6.< / b >
封裝
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< b > 7.< / b >
接口
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< b > 7.1.< / b >
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接口是合約
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< li class = "chapter " data-level = "7.2" data-path = "ch7/ch7-02.html" >
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< b > 7.2.< / b >
接口類型
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< li class = "chapter " data-level = "7.3" data-path = "ch7/ch7-03.html" >
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< b > 7.3.< / b >
實現接口的條件
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< li class = "chapter " data-level = "7.4" data-path = "ch7/ch7-04.html" >
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< b > 7.4.< / b >
flag.Value接口
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< b > 7.5.< / b >
接口值
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< b > 7.6.< / b >
sort.Interface接口
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< b > 7.7.< / b >
http.Handler接口
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< b > 7.8.< / b >
error接口
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< a href = "../ch7/ch7-09.html" >
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< b > 7.9.< / b >
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示例: 表達式求值
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< b > 7.10.< / b >
類型斷言
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< b > 7.11.< / b >
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基於類型斷言識别錯誤類型
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< b > 7.12.< / b >
通過類型斷言査詢接口
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< b > 7.13.< / b >
類型分支
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< b > 7.14.< / b >
示例: 基於標記的XML解碼
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< / li >
< li class = "chapter " data-level = "7.15" data-path = "ch7/ch7-15.html" >
< a href = "../ch7/ch7-15.html" >
< i class = "fa fa-check" > < / i >
< b > 7.15.< / b >
補充幾點
< / a >
< / li >
< / ul >
< / li >
< li class = "chapter " data-level = "8" data-path = "ch8/ch8.html" >
< a href = "../ch8/ch8.html" >
< i class = "fa fa-check" > < / i >
< b > 8.< / b >
Goroutines和Channels
< / a >
< ul class = "articles" >
< li class = "chapter " data-level = "8.1" data-path = "ch8/ch8-01.html" >
< a href = "../ch8/ch8-01.html" >
< i class = "fa fa-check" > < / i >
< b > 8.1.< / b >
Goroutines
< / a >
< / li >
< li class = "chapter " data-level = "8.2" data-path = "ch8/ch8-02.html" >
< a href = "../ch8/ch8-02.html" >
< i class = "fa fa-check" > < / i >
< b > 8.2.< / b >
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示例: 併發的Clock服務
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< / a >
< / li >
< li class = "chapter " data-level = "8.3" data-path = "ch8/ch8-03.html" >
< a href = "../ch8/ch8-03.html" >
< i class = "fa fa-check" > < / i >
< b > 8.3.< / b >
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示例: 併發的Echo服務
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< / a >
< / li >
< li class = "chapter " data-level = "8.4" data-path = "ch8/ch8-04.html" >
< a href = "../ch8/ch8-04.html" >
< i class = "fa fa-check" > < / i >
< b > 8.4.< / b >
Channels
< / a >
< / li >
< li class = "chapter " data-level = "8.5" data-path = "ch8/ch8-05.html" >
< a href = "../ch8/ch8-05.html" >
< i class = "fa fa-check" > < / i >
< b > 8.5.< / b >
併行的循環
< / a >
< / li >
< li class = "chapter " data-level = "8.6" data-path = "ch8/ch8-06.html" >
< a href = "../ch8/ch8-06.html" >
< i class = "fa fa-check" > < / i >
< b > 8.6.< / b >
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示例: 併發的Web爬蟲
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< / a >
< / li >
< li class = "chapter " data-level = "8.7" data-path = "ch8/ch8-07.html" >
< a href = "../ch8/ch8-07.html" >
< i class = "fa fa-check" > < / i >
< b > 8.7.< / b >
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基於select的多路複用
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< / a >
< / li >
< li class = "chapter " data-level = "8.8" data-path = "ch8/ch8-08.html" >
< a href = "../ch8/ch8-08.html" >
< i class = "fa fa-check" > < / i >
< b > 8.8.< / b >
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示例: 併發的字典遍歷
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< / a >
< / li >
< li class = "chapter " data-level = "8.9" data-path = "ch8/ch8-09.html" >
< a href = "../ch8/ch8-09.html" >
< i class = "fa fa-check" > < / i >
< b > 8.9.< / b >
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併發的退齣
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< / a >
< / li >
< li class = "chapter " data-level = "8.10" data-path = "ch8/ch8-10.html" >
< a href = "../ch8/ch8-10.html" >
< i class = "fa fa-check" > < / i >
< b > 8.10.< / b >
示例: 聊天服務
< / a >
< / li >
< / ul >
< / li >
< li class = "chapter " data-level = "9" data-path = "ch9/ch9.html" >
< a href = "../ch9/ch9.html" >
< i class = "fa fa-check" > < / i >
< b > 9.< / b >
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基於共享變量的併發
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< / a >
< ul class = "articles" >
< li class = "chapter " data-level = "9.1" data-path = "ch9/ch9-01.html" >
< a href = "../ch9/ch9-01.html" >
< i class = "fa fa-check" > < / i >
< b > 9.1.< / b >
競爭條件
< / a >
< / li >
< li class = "chapter " data-level = "9.2" data-path = "ch9/ch9-02.html" >
< a href = "../ch9/ch9-02.html" >
< i class = "fa fa-check" > < / i >
< b > 9.2.< / b >
sync.Mutex互斥鎖
< / a >
< / li >
< li class = "chapter " data-level = "9.3" data-path = "ch9/ch9-03.html" >
< a href = "../ch9/ch9-03.html" >
< i class = "fa fa-check" > < / i >
< b > 9.3.< / b >
sync.RWMutex讀寫鎖
< / a >
< / li >
< li class = "chapter " data-level = "9.4" data-path = "ch9/ch9-04.html" >
< a href = "../ch9/ch9-04.html" >
< i class = "fa fa-check" > < / i >
< b > 9.4.< / b >
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內存同步
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< / a >
< / li >
< li class = "chapter " data-level = "9.5" data-path = "ch9/ch9-05.html" >
< a href = "../ch9/ch9-05.html" >
< i class = "fa fa-check" > < / i >
< b > 9.5.< / b >
sync.Once初始化
< / a >
< / li >
< li class = "chapter " data-level = "9.6" data-path = "ch9/ch9-06.html" >
< a href = "../ch9/ch9-06.html" >
< i class = "fa fa-check" > < / i >
< b > 9.6.< / b >
競爭條件檢測
< / a >
< / li >
< li class = "chapter " data-level = "9.7" data-path = "ch9/ch9-07.html" >
< a href = "../ch9/ch9-07.html" >
< i class = "fa fa-check" > < / i >
< b > 9.7.< / b >
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示例: 併發的非阻塞緩存
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< / a >
< / li >
< li class = "chapter " data-level = "9.8" data-path = "ch9/ch9-08.html" >
< a href = "../ch9/ch9-08.html" >
< i class = "fa fa-check" > < / i >
< b > 9.8.< / b >
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Goroutines和線程
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< / a >
< / li >
< / ul >
< / li >
< li class = "chapter " data-level = "10" data-path = "ch10/ch10.html" >
< a href = "../ch10/ch10.html" >
< i class = "fa fa-check" > < / i >
< b > 10.< / b >
包和工具
< / a >
< ul class = "articles" >
< li class = "chapter " data-level = "10.1" data-path = "ch10/ch10-01.html" >
< a href = "../ch10/ch10-01.html" >
< i class = "fa fa-check" > < / i >
< b > 10.1.< / b >
簡介
< / a >
< / li >
< li class = "chapter " data-level = "10.2" data-path = "ch10/ch10-02.html" >
< a href = "../ch10/ch10-02.html" >
< i class = "fa fa-check" > < / i >
< b > 10.2.< / b >
導入路徑
< / a >
< / li >
< li class = "chapter " data-level = "10.3" data-path = "ch10/ch10-03.html" >
< a href = "../ch10/ch10-03.html" >
< i class = "fa fa-check" > < / i >
< b > 10.3.< / b >
包聲明
< / a >
< / li >
< li class = "chapter " data-level = "10.4" data-path = "ch10/ch10-04.html" >
< a href = "../ch10/ch10-04.html" >
< i class = "fa fa-check" > < / i >
< b > 10.4.< / b >
導入聲明
< / a >
< / li >
< li class = "chapter " data-level = "10.5" data-path = "ch10/ch10-05.html" >
< a href = "../ch10/ch10-05.html" >
< i class = "fa fa-check" > < / i >
< b > 10.5.< / b >
匿名導入
< / a >
< / li >
< li class = "chapter " data-level = "10.6" data-path = "ch10/ch10-06.html" >
< a href = "../ch10/ch10-06.html" >
< i class = "fa fa-check" > < / i >
< b > 10.6.< / b >
包和命名
< / a >
< / li >
< li class = "chapter " data-level = "10.7" data-path = "ch10/ch10-07.html" >
< a href = "../ch10/ch10-07.html" >
< i class = "fa fa-check" > < / i >
< b > 10.7.< / b >
工具
< / a >
< / li >
< / ul >
< / li >
< li class = "chapter " data-level = "11" data-path = "ch11/ch11.html" >
< a href = "../ch11/ch11.html" >
< i class = "fa fa-check" > < / i >
< b > 11.< / b >
測試
< / a >
< ul class = "articles" >
< li class = "chapter " data-level = "11.1" data-path = "ch11/ch11-01.html" >
< a href = "../ch11/ch11-01.html" >
< i class = "fa fa-check" > < / i >
< b > 11.1.< / b >
go test
< / a >
< / li >
< li class = "chapter " data-level = "11.2" data-path = "ch11/ch11-02.html" >
< a href = "../ch11/ch11-02.html" >
< i class = "fa fa-check" > < / i >
< b > 11.2.< / b >
測試函數
< / a >
< / li >
< li class = "chapter " data-level = "11.3" data-path = "ch11/ch11-03.html" >
< a href = "../ch11/ch11-03.html" >
< i class = "fa fa-check" > < / i >
< b > 11.3.< / b >
測試覆蓋率
< / a >
< / li >
< li class = "chapter " data-level = "11.4" data-path = "ch11/ch11-04.html" >
< a href = "../ch11/ch11-04.html" >
< i class = "fa fa-check" > < / i >
< b > 11.4.< / b >
基準測試
< / a >
< / li >
< li class = "chapter active" data-level = "11.5" data-path = "ch11/ch11-05.html" >
< a href = "../ch11/ch11-05.html" >
< i class = "fa fa-check" > < / i >
< b > 11.5.< / b >
剖析
< / a >
< / li >
< li class = "chapter " data-level = "11.6" data-path = "ch11/ch11-06.html" >
< a href = "../ch11/ch11-06.html" >
< i class = "fa fa-check" > < / i >
< b > 11.6.< / b >
示例函數
< / a >
< / li >
< / ul >
< / li >
< li class = "chapter " data-level = "12" data-path = "ch12/ch12.html" >
< a href = "../ch12/ch12.html" >
< i class = "fa fa-check" > < / i >
< b > 12.< / b >
反射
< / a >
< ul class = "articles" >
< li class = "chapter " data-level = "12.1" data-path = "ch12/ch12-01.html" >
< a href = "../ch12/ch12-01.html" >
< i class = "fa fa-check" > < / i >
< b > 12.1.< / b >
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爲何需要反射?
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< / a >
< / li >
< li class = "chapter " data-level = "12.2" data-path = "ch12/ch12-02.html" >
< a href = "../ch12/ch12-02.html" >
< i class = "fa fa-check" > < / i >
< b > 12.2.< / b >
reflect.Type和reflect.Value
< / a >
< / li >
< li class = "chapter " data-level = "12.3" data-path = "ch12/ch12-03.html" >
< a href = "../ch12/ch12-03.html" >
< i class = "fa fa-check" > < / i >
< b > 12.3.< / b >
Display遞歸打印
< / a >
< / li >
< li class = "chapter " data-level = "12.4" data-path = "ch12/ch12-04.html" >
< a href = "../ch12/ch12-04.html" >
< i class = "fa fa-check" > < / i >
< b > 12.4.< / b >
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示例: 編碼S表達式
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< / a >
< / li >
< li class = "chapter " data-level = "12.5" data-path = "ch12/ch12-05.html" >
< a href = "../ch12/ch12-05.html" >
< i class = "fa fa-check" > < / i >
< b > 12.5.< / b >
通過reflect.Value脩改值
< / a >
< / li >
< li class = "chapter " data-level = "12.6" data-path = "ch12/ch12-06.html" >
< a href = "../ch12/ch12-06.html" >
< i class = "fa fa-check" > < / i >
< b > 12.6.< / b >
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示例: 解碼S表達式
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< / a >
< / li >
< li class = "chapter " data-level = "12.7" data-path = "ch12/ch12-07.html" >
< a href = "../ch12/ch12-07.html" >
< i class = "fa fa-check" > < / i >
< b > 12.7.< / b >
穫取結構體字段標識
< / a >
< / li >
< li class = "chapter " data-level = "12.8" data-path = "ch12/ch12-08.html" >
< a href = "../ch12/ch12-08.html" >
< i class = "fa fa-check" > < / i >
< b > 12.8.< / b >
顯示一個類型的方法集
< / a >
< / li >
< li class = "chapter " data-level = "12.9" data-path = "ch12/ch12-09.html" >
< a href = "../ch12/ch12-09.html" >
< i class = "fa fa-check" > < / i >
< b > 12.9.< / b >
幾點忠告
< / a >
< / li >
< / ul >
< / li >
< li class = "chapter " data-level = "13" data-path = "ch13/ch13.html" >
< a href = "../ch13/ch13.html" >
< i class = "fa fa-check" > < / i >
< b > 13.< / b >
底層編程
< / a >
< ul class = "articles" >
< li class = "chapter " data-level = "13.1" data-path = "ch13/ch13-01.html" >
< a href = "../ch13/ch13-01.html" >
< i class = "fa fa-check" > < / i >
< b > 13.1.< / b >
unsafe.Sizeof, Alignof 和 Offsetof
< / a >
< / li >
< li class = "chapter " data-level = "13.2" data-path = "ch13/ch13-02.html" >
< a href = "../ch13/ch13-02.html" >
< i class = "fa fa-check" > < / i >
< b > 13.2.< / b >
unsafe.Pointer
< / a >
< / li >
< li class = "chapter " data-level = "13.3" data-path = "ch13/ch13-03.html" >
< a href = "../ch13/ch13-03.html" >
< i class = "fa fa-check" > < / i >
< b > 13.3.< / b >
示例: 深度相等判斷
< / a >
< / li >
< li class = "chapter " data-level = "13.4" data-path = "ch13/ch13-04.html" >
< a href = "../ch13/ch13-04.html" >
< i class = "fa fa-check" > < / i >
< b > 13.4.< / b >
通過cgo調用C代碼
< / a >
< / li >
< li class = "chapter " data-level = "13.5" data-path = "ch13/ch13-05.html" >
< a href = "../ch13/ch13-05.html" >
< i class = "fa fa-check" > < / i >
< b > 13.5.< / b >
幾點忠告
< / a >
< / li >
< / ul >
< / li >
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< li class = "chapter " data-level = "14" data-path = "errata.html" >
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< a href = "../errata.html" >
< i class = "fa fa-check" > < / i >
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< b > 14.< / b >
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勘誤
< / a >
< / li >
< li class = "divider" > < / li >
< li >
< a href = "https://www.gitbook.com" target = "blank" class = "gitbook-link" >
本書使用 GitBook 釋出
< / a >
< / li >
< / ul >
< / nav >
< / div >
< div class = "book-body" >
< div class = "body-inner" >
< div class = "book-header" role = "navigation" >
<!-- Actions Left -->
<!-- Title -->
< h1 >
< i class = "fa fa-circle-o-notch fa-spin" > < / i >
< a href = "../" > Go编程语言< / a >
< / h1 >
< / div >
< div class = "page-wrapper" tabindex = "-1" role = "main" >
< div class = "page-inner" >
< section class = "normal" id = "section-" >
< h2 id = "115-剖析" > 11.5. 剖 析 < / h2 >
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< p > 測 量 基 準 對 於 衡 量 特 定 操 作 的 性 能 是 有 幫 助 的 , 但 是 , 當 我 們 視 圖 讓 程 序 跑 的 更 快 的 時 候 , 我 們 通 常 併 不 知 道 從 哪 里 開 始 優 化 . 每 個 碼 農 都 應 該 知 道 Donald Knuth 在 1974年 的 ‘ ‘ Structured Programming with go to Statements’ ’ 上 所 説 的 格 言 . 雖 然 經 常 被 解 讀 爲 不 重 視 性 能 的 意 思 , 但 是 從 原 文 我 們 可 以 看 到 不 同 的 含 義 :< / p >
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< blockquote >
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< p > 毫 無 疑 問 , 效 率 會 導 致 各 種 濫 用 . 程 序 員 需 要 浪 費 大 量 的 時 間 思 考 , 或 者 擔 心 , 被 部 分 程 序 的 速 度 所 榦 擾 , 實 際 上 這 些 嚐 試 提 陞 效 率 的 行 爲 可 能 産 生 強 烈 的 負 面 影 響 , 特 别 是 當 調 試 和 維 護 的 時 候 . 我 們 不 應 該 過 度 糾 結 於 細 節 的 優 化 , 應 該 説 約 97%的 場 景 : 過 早 的 優 化 是 萬 惡 之 源 .< / p >
< p > 我 們 當 然 不 應 該 放 棄 那 關 鍵 的 3%的 機 會 . 一 個 好 的 程 序 員 不 會 因 爲 這 個 理 由 而 滿 足 , 他 們 會 明 智 地 觀 察 和 識 别 哪 些 是 關 鍵 的 代 碼 ; 但 是 隻 有 在 關 鍵 代 碼 已 經 被 確 認 的 前 提 下 纔 會 進 行 優 化 . 對 於 判 斷 哪 些 部 分 是 關 鍵 代 碼 是 經 常 容 易 犯 經 驗 性 錯 誤 的 地 方 , 因 此 程 序 員 普 通 使 用 的 測 量 工 具 , 使 得 他 們 的 直 覺 很 不 靠 譜 .< / p >
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< / blockquote >
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< p > 當 我 們 想 仔 細 觀 察 我 們 程 序 的 運 行 速 度 的 時 候 , 最 好 的 技 術 是 如 何 識 别 關 鍵 代 碼 . 自 動 化 的 剖 析 技 術 是 基 於 程 序 執 行 期 間 一 些 抽 樣 數 據 , 然 後 推 斷 後 面 的 執 行 狀 態 ; 最 終 産 生 一 個 運 行 時 間 的 統 計 數 據 文 件 .< / p >
< p > Go語 言 支 持 多 種 類 型 的 剖 析 性 能 分 析 , 每 一 種 關 註 不 同 的 方 面 , 但 它 們 都 涉 及 到 每 個 采 樣 記 録 的 感 興 趣 的 一 繫 列 事 件 消 息 , 每 個 事 件 都 包 含 函 數 調 用 時 函 數 調 用 堆 棧 的 信 息 . 內 建 的 < code > go test< / code > 工 具 對 幾 種 分 析 方 式 都 提 供 了 支 持 .< / p >
< p > CPU分 析 文 件 標 識 了 函 數 執 行 時 所 需 要 的 CPU時 間 . 當 前 運 行 的 繫 統 線 程 在 每 隔 幾 毫 秒 都 會 遇 到 操 作 繫 統 的 中 斷 事 件 , 每 次 中 斷 時 都 會 記 録 一 個 分 析 文 件 然 後 恢 複 正 常 的 運 行 .< / p >
< p > 堆 分 析 則 記 録 了 程 序 的 內 存 使 用 情 況 . 每 個 內 存 分 配 操 作 都 會 觸 發 內 部 平 均 內 存 分 配 例 程 , 每 個 512KB 的 內 存 申 請 都 會 觸 發 一 個 事 件 .< / p >
< p > 阻 塞 分 析 則 記 録 了 goroutine最 大 的 阻 塞 操 作 , 例 如 繫 統 調 用 , 管 道 發 送 和 接 收 , 還 有 穫 取 鎖 等 . 分 析 庫 會 記 録 每 個 goroutine被 阻 塞 時 的 相 關 操 作 .< / p >
< p > 在 測 試 環 境 下 隻 需 要 一 個 標 誌 參 數 就 可 以 生 成 各 種 分 析 文 件 . 當 一 次 使 用 多 個 標 誌 參 數 時 需 要 當 心 , 因 爲 分 析 操 作 本 身 也 可 能 會 影 像 程 序 的 運 行 .< / p >
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< pre > < code > $ go test -cpuprofile=cpu.out
$ go test -blockprofile=block.out
$ go test -memprofile=mem.out
2015-12-21 04:55:18 +00:00
< / code > < / pre > < p > 對 於 一 些 非 測 試 程 序 也 很 容 易 支 持 分 析 的 特 性 , 具 體 的 實 現 方 式 和 程 序 是 短 時 間 運 行 的 小 工 具 還 是 長 時 間 運 行 的 服 務 會 有 很 大 不 同 , 因 此 Go的 runtim運 行 時 包 提 供 了 程 序 運 行 時 控 製 分 析 特 性 的 接 口 .< / p >
< p > 一 旦 我 們 已 經 收 集 到 了 用 於 分 析 的 采 樣 數 據 , 我 們 就 可 以 使 用 pprof 據 來 分 析 這 些 數 據 . 這 是 Go工 具 箱 自 帶 的 一 個 工 具 , 但 併 不 是 一 個 日 常 工 具 , 它 對 應 < code > go tool pprof< / code > 命 令 . 該 命 令 有 許 多 特 性 和 選 項 , 但 是 最 重 要 的 有 兩 個 , 就 是 生 成 這 個 概 要 文 件 的 可 執 行 程 序 和 對 於 的 分 析 日 誌 文 件 .< / p >
< p > 爲 了 提 高 分 析 效 率 和 減 少 空 間 , 分 析 日 誌 本 身 併 不 包 含 函 數 的 名 字 ; 它 隻 包 含 函 數 對 應 的 地 址 . 也 就 是 説 pprof需 要 和 分 析 日 誌 對 於 的 可 執 行 程 序 . 雖 然 < code > go test< / code > 命 令 通 常 會 丟 棄 臨 時 用 的 測 試 程 序 , 但 是 在 啟 用 分 析 的 時 候 會 將 測 試 程 序 保 存 爲 foo.test 文 件 , 其 中 foo 部 分 對 於 測 試 包 的 名 字 .< / p >
< p > 下 面 的 命 令 演 示 了 如 何 生 成 一 個 CPU分 析 文 件 . 我 們 選 擇 < code > net/http< / code > 包 的 一 個 基 準 測 試 . 通 常 是 基 於 一 個 已 經 確 定 了 是 關 鍵 代 碼 的 部 分 進 行 基 準 測 試 . 基 準 測 試 會 默 認 包 含 單 元 測 試 , 這 里 我 們 用 -run=NONE 禁 止 單 元 測 試 .< / p >
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< pre > < code > $ go test -run=NONE -bench=ClientServerParallelTLS64 \
-cpuprofile=cpu.log net/http
PASS
BenchmarkClientServerParallelTLS64-8 1000
3141325 ns/op 143010 B/op 1747 allocs/op
ok net/http 3.395s
$ go tool pprof -text -nodecount=10 ./http.test cpu.log
2570ms of 3590ms total (71.59%)
Dropped 129 nodes (cum < = 17.95ms)
Showing top 10 nodes out of 166 (cum > = 60ms)
flat flat% sum% cum cum%
1730ms 48.19% 48.19% 1750ms 48.75% crypto/elliptic.p256ReduceDegree
230ms 6.41% 54.60% 250ms 6.96% crypto/elliptic.p256Diff
120ms 3.34% 57.94% 120ms 3.34% math/big.addMulVVW
110ms 3.06% 61.00% 110ms 3.06% syscall.Syscall
90ms 2.51% 63.51% 1130ms 31.48% crypto/elliptic.p256Square
70ms 1.95% 65.46% 120ms 3.34% runtime.scanobject
60ms 1.67% 67.13% 830ms 23.12% crypto/elliptic.p256Mul
60ms 1.67% 68.80% 190ms 5.29% math/big.nat.montgomery
50ms 1.39% 70.19% 50ms 1.39% crypto/elliptic.p256ReduceCarry
50ms 1.39% 71.59% 60ms 1.67% crypto/elliptic.p256Sum
2015-12-21 04:55:18 +00:00
< / code > < / pre > < p > 參 數 < code > -text< / code > 標 誌 參 數 用 於 指 定 輸 齣 格 式 , 在 這 里 每 行 是 一 個 函 數 , 根 據 使 用 CPU的 時 間 來 排 序 . 其 中 < code > -nodecount=10< / code > 標 誌 參 數 限 製 了 隻 輸 齣 前 10行 的 結 果 . 對 於 嚴 重 的 性 能 問 題 , 這 個 文 本 格 式 基 本 可 以 幫 助 査 明 原 因 了 .< / p >
< p > 這 個 概 要 文 件 告 訴 我 們 , HTTPS基 準 測 試 中 < code > crypto/elliptic.p256ReduceDegree< / code > 函 數 占 用 了 將 近 一 般 的 CPU資 源 . 相 比 之 下 , 如 果 一 個 概 要 文 件 中 主 要 是 runtime包 的 內 存 分 配 的 函 數 , 那 麽 減 少 內 存 消 耗 可 能 是 一 個 值 得 嚐 試 的 優 化 策 略 .< / p >
< p > 對 於 一 些 更 微 妙 的 問 題 , 你 可 能 需 要 使 用 pprof 的 圖 形 顯 示 功 能 . 這 個 需 要 安 裝 GraphViz 工 具 , 可 以 從 www.graphviz.org 下 載 . 參 數 < code > -web< / code > 用 於 生 成 一 個 有 向 圖 文 件 , 包 含 CPU的 使 用 和 最 特 點 的 函 數 等 信 息 .< / p >
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< p > 這 一 節 我 們 隻 是 簡 單 看 了 下 Go語 言 的 分 析 據 工 具 . 如 果 想 了 解 更 多 , 可 以 閲 讀 Go官 方 博 客 的 ‘ ‘ Profi ling Go Programs’ ’ 一 文 .< / p >
2015-12-09 07:57:17 +00:00
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