1. Problems
Tao He
elfinhe@gmail.com
@SELAB, SYSU
2010,May
About 90 minutes
1/20

2. Themes
 Hackerdom
 Programming Languages
2/49

3. Fascinating Problems
 “The world is full of fascinating
problems waiting to be solved.”
Eric Raymond, How to become a hacker
Eric Raymond. How To Become A Hacker. http://catb.org/~esr/faqs/hacker-howto.html
Eric Raymond. The Cathedral and the Bazaar. http://catb.org/esr/writings/homesteading/
3/49

4. Hacker
 Not Cracker, But Creator
 Eager to Communicate
4/49

5. FLOSS community
 Not only Free Source
 But an Efficiency Way
to Communicate, Study and Work
 Tashi
 “Talk is cheap. Show me the code.” Linus
FLOSS: Free-Libre and Open Source Software
5/49

6. IF NOT OPEN?
 Information Inequality
 Esoterica
 Design Patterns
 No Feedback
Herbert Schiller. Information Inequality: The Deepening Social Crisis in America, Routledge 1995, ISBN 0415907659
6/49

7. KISS: Keep It Simple and Stupid
 “Perfection (in design) is achieved not when
there is nothing more to add, but rather when
there is nothing more to take away.”
 Linux
 Fid
 Process
 Memory
 Design Patterns
7/49

8. Tools
 Everything
8/49

9. Tools
 Lingoes
9/49

10. Tools
 Wakoopa
10/49

11. Tools
 SuperMemo
11/49

12. Thank you!
12/49

13. Themes
 Hackerdom
 Programming Languages
13/49

14. Why we use Programming
Languages?
 For customers
 To meet their requirements. ( For example , OA
systems)
 For machine ( Von Neumann Architecture )
 Instruction flow
 Data
 Strange, isn’t it ?
14/49

15. Other Problems
 Common Elements in High-Level
Languages?
 Dynamic ?
 Syntax, Semantics and Pragmatics ?
 Semantics and Logic?
15/49

16. Assembler Language
16/49

17. Assembler Language
 Macro of Machine Code
 While Programming
 Registers
 Data Seg
 Code Seg
 Stack Seg
 Von Neumann Architecture
 Instruction fetch
 Instruction execute
17/49

18. We have Data Seg already.
Why we need Stack Seg ?
 Modules
 But Stack is manual
18/49

19. Why we need Modules ?
 Recursion
 Reusability
 Scope Encapsulation
19/49

20. Stacks and Modules’ Disadvantages
 Time
 Space: Stack Overflow
20/49

21. The C Programming Language
21/49

22. What’s NEW in C
 Expressions (Formal Languages,
Automaton )
 For Instruction
 Arithmetic Expressions ( 3+2-5*3 )
 Control Flow Expressions ( for, if…else…, )
 Function Expressions
 For Data
 Type System
 Atom
 Structure
 We have a Compiler now
22/49

23. Advantages from Expressions
 Human
 For Instruction
 Arithmetic Expressions ( 3+2-5*3 )
 Control Flow Expressions ( for, if…else…, )
 Function Expressions
 For Data
 Type System
 Atom
 Structure
23/49

24. Advantages from Compiler
 Expressions
 Modules : Stack is Automatic
 Code Optimization ( Inline, Tail Recursion )
24/49

25. Compile-time vs. Run-time in C
 Compile-time
 Type Information
 Function Information
 Run-time
 null
25/49

26. The C++ Programming Language
26/49

27. What’s NEW in C++?
 Paradigms
 Class Member Functions
 Inheritance Hierarchies
 Virtual Function & Virtual Inherit
 Template
27/49

28. Paradigms in C++
 Procedural
 ADT
 OO
28/49

29. Class Member Functions
 Special Code
 ___ClsA_Func2(..., ClsA *this)
29/49

30. Inheritance Hierarchies
 Almost Compile-time
 Virtual: Run-time
30/49

31. C++ want to be as Efficiency as C
 It’s all right for Procedural and ADT
 But not for OO with Virtual
 No Run-time Hierarchies Meta-data for
Polymorphism
31/49

32. Virtual Function:
Virtual Function Table
32/49

33. Inheritance
 Single Inheritance
 Multiple Inheritance
 Single Virtual Inheritance
 Multiple Virtual Inheritance
33/49

34. Virtual Inheritance: Virtual Base Table
34/49

35. Compile-time vs. Run-time in C++
 Compile-time
 Inheritance Hierarchies Information
 Function Information
 Run-time ( Dynamic )
 Virtual Function Table
 Virtual Base Table
35/49

36. Cross-Platform in C++?
 Source-Level: Yes
 Cross-Platform is Manual for different OS API
 Execution-Level : No
36/49

37. What is not Efficiency C++?
 Run-time
 Virtual Function
 Virtual Inheritance
 Virtual Base Class without Virtual Function and
Data will be optimized.
 Java can Multiple Implement Interfaces.
 Compile-time
 Inheritance Hierarchies
37/49

38. The Java Programming Language
Mark Stoodley. Issues in static and dynamic native Java code compilation.
http://www.ibm.com/developerworks/java/library/j-rtj2/index.html
38/49

39. What’s NEW in Java?
 JVM
 Dynamic Compilation
39/49

40. 虚拟机的好处有什么？
 跨平台：在 OS 与字节码间隔了一层。实
现了程序员无负担的跨平台。
 动态编译：许多信息不必在编译后确定，
为动态特性提供可能，稍后详细说。
 运行时维护着类型信息，甚至可以加载新
的类型。（ CORBRA 依赖这个实现。）
40/49

41. Java 编译执行的过程是怎样的？
 编译后产生一个基于堆栈的字节码
 JRE 在不同的 OS 上提供支持
 起初的 JRE 是解释执行的，效率低下。
 获取待执行的下一个字节码。
 解码。
 从操作数堆栈获取所需的操作数。
 按照 JVM 规范执行操作。
 将结果写回堆栈。
41/49

42. Java 如何解决执行效率低下问题
？
42/49

43. JIT 是怎样运行的呢？
 每次按照一个 function 来编译
 转成中间表示，并优化，转成可执行码
 编译线程和执行线程
 分析框架 Profiler 观察程序行为
 例如热点 function 内部对象维持一个池。
43/49

44. 动态编译的优点有什么？
 学习程序的行为并优化
 频繁执行的 function—— 热方法
 arrayCopy 方法，拷贝大段内存，特殊指令
 例如类层次结构，多态的优化。
 （大多数虚调用都有其固定的一个目标， JIT 因
此生成的代码比虚表调用代码的效率会更高。）
44/49

45. 动态编译的缺点有什么？
 初始编译会影响启动时间。
 运行时编译，行为分析需要花费时间。
 运行效率达到稳定需要时间。
 GUI 不能忍受动态编译和 GC 带来的延迟
。
45/49

46. Java 如何解决实时的需求？
 AOT （ Ahead-of-time ）编译器
 预先编译成为可执行码
46/49

47. 47/49

48. Java 适合怎样的应用呢？
 Java 比较时候需要长期运行的应用，
 Web 服务器
 Daemon 服务
48/49

49. Thank you!
49/49