1.
Optimizing software in C++
An optimization guide for Windows, Linux and Mac
platforms
By Agner Fog. Copenhagen University College of Engineering.
Copyright © 2004 - 2011. Last updated 2011-01-30.
Contents
1 Introduction ....................................................................................................................... 3
1.1 The costs of optimizing ............................................................................................... 4
2 Choosing the optimal platform........................................................................................... 4
2.1 Choice of hardware platform....................................................................................... 4
2.2 Choice of microprocessor ........................................................................................... 6
2.3 Choice of operating system......................................................................................... 6
2.4 Choice of programming language ............................................................................... 7
2.5 Choice of compiler ...................................................................................................... 9
2.6 Choice of function libraries........................................................................................ 11
2.7 Choice of user interface framework........................................................................... 13
2.8 Overcoming the drawbacks of the C++ language...................................................... 14
3 Finding the biggest time consumers ................................................................................ 15
3.1 How much is a clock cycle? ...................................................................................... 15
3.2 Use a profiler to find hot spots .................................................................................. 16
3.3 Program installation .................................................................................................. 18
3.4 Automatic updates .................................................................................................... 18
3.5 Program loading ....................................................................................................... 19
3.6 Dynamic linking and position-independent code ....................................................... 19
3.7 File access................................................................................................................ 21
3.8 System database...................................................................................................... 21
3.9 Other databases ....................................................................................................... 21
3.10 Graphics and other system resources..................................................................... 22
3.11 Network access ...................................................................................................... 22
3.12 Memory access....................................................................................................... 22
3.13 Context switches..................................................................................................... 22
3.14 Dependency chains ................................................................................................ 23
3.15 Execution unit throughput ....................................................................................... 23
4 Performance and usability ............................................................................................... 23
5 Choosing the optimal algorithm ....................................................................................... 25
6 Development process...................................................................................................... 26
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 ...................................................................... 31
7.4 Enums ...................................................................................................................... 33
7.5 Booleans................................................................................................................... 33
7.6 Pointers and references............................................................................................ 36
7.7 Function pointers ...................................................................................................... 37
7.8 Member pointers....................................................................................................... 37
7.9 Smart pointers .......................................................................................................... 38
7.10 Arrays .....................................................................................................................38
7.11 Type conversions.................................................................................................... 40
7.12 Branches and switch statements............................................................................. 43
7.13 Loops......................................................................................................................45
7.14 Functions................................................................................................................ 47
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