1.
Optimizing software in C++
An optimization guide for Windows, Linux and Mac
platforms
By Agner Fog. Technical University of Denmark.
Copyright © 2004 - 2017. Last updated 2017-05-02.
Contents
1 Introduction ....................................................................................................................... 3
1.1 The costs of optimizing ............................................................................................... 4
2 Choosing the optimal platform ........................................................................................... 5
2.1 Choice of hardware platform ....................................................................................... 5
2.2 Choice of microprocessor ........................................................................................... 6
2.3 Choice of operating system ......................................................................................... 6
2.4 Choice of programming language ............................................................................... 8
2.5 Choice of compiler .................................................................................................... 10
2.6 Choice of function libraries ........................................................................................ 12
2.7 Choice of user interface framework ........................................................................... 14
2.8 Overcoming the drawbacks of the C++ language ...................................................... 14
3 Finding the biggest time consumers ................................................................................ 16
3.1 How much is a clock cycle? ...................................................................................... 16
3.2 Use a profiler to find hot spots .................................................................................. 16
3.3 Program installation .................................................................................................. 18
3.4 Automatic updates .................................................................................................... 19
3.5 Program loading ....................................................................................................... 19
3.6 Dynamic linking and position-independent code ....................................................... 20
3.7 File access ................................................................................................................ 20
3.8 System database ...................................................................................................... 20
3.9 Other databases ....................................................................................................... 21
3.10 Graphics ................................................................................................................. 21
3.11 Other system resources .......................................................................................... 21
3.12 Network access ...................................................................................................... 21
3.13 Memory access ....................................................................................................... 22
3.14 Context switches ..................................................................................................... 22
3.15 Dependency chains ................................................................................................ 22
3.16 Execution unit throughput ....................................................................................... 22
4 Performance and usability ............................................................................................... 23
5 Choosing the optimal algorithm ....................................................................................... 24
6 Development process ...................................................................................................... 25
7 The efficiency of different C++ constructs ........................................................................ 26
7.1 Different kinds of variable storage ............................................................................. 26
7.2 Integers variables and operators ............................................................................... 29
7.3 Floating point variables and operators ...................................................................... 32
7.4 Enums ...................................................................................................................... 33
7.5 Booleans ................................................................................................................... 34
7.6 Pointers and references ............................................................................................ 36
7.7 Function pointers ...................................................................................................... 37
7.8 Member pointers ....................................................................................................... 38
7.9 Smart pointers .......................................................................................................... 38
7.10 Arrays ..................................................................................................................... 39
7.11 Type conversions .................................................................................................... 40
7.12 Branches and switch statements ............................................................................. 44
7.13 Loops ...................................................................................................................... 45
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