General C++ Performance Improvement Tips [closed]

Answer 1

This one will have very good Techniques for general c++ Optimization:

http://www.tantalon.com/pete/cppopt/main.htm

Use the profiler to see what part of application running slowly and then use the optimizing techniques.

I used the valgrind with callgrind tool for the profiling purpose and it will give you which lines cost how much.

valgrind --tool=callgrind

Answer 2

This page sum up all you have to know about optimization in C++ (be it while or after writing software). It's really good advice and is very lear -- and can be used as a useful reminder in optimization phase on a project.

It's a bit old so you also have to know wich optimizations are already done by your compiler (like NRVO).

Other than that, reading the Effective C++, More Effective C++, Effective STL and C++ Coding Standards that have already been cited is important too, because it explains a lot of things about what occurs in the language and in the STL, allowing you to better optimize your specific case by using a better understanding of what's happening exactly.

Answer 3

Here's a list I've referred to in the past - http://www.devx.com/cplus/Article/16328/0/page/1. Beyond that, Googling c++ performance tips yields quite a bit.

Answer 4

I took the habit to prefer writing ++i rather than i++ not that it brings any performance boost when i is an int but things are different when i is an iterator which might have a complex implementation.

Then let's say you come from the C programming language, lose your habit to declare all your variables at the beginning on the function: declare your variables when they are needed in the function flow since the function might contain early return statements before some variables that were initialized at the beginning are effectively used.

Apart from that, another resource is C++ Coding Standards: 101 Rules, Guidelines, and Best Practices by Herb Sutter (him again) and Alexei Alexandrescu.

There is also a more recent edition of Scott Meyers' Effective C++: Effective C++: 55 specific ways to improve your programs and designs.

Finally, I would like to mention Tony Albrecht's Pitfalls of Object Oriented Programming presentation: not that it contains rules of thumb you can follow blindly but it's a very interesting read.

Answer 5

Here is a nice article on the topic: How To Go Slow

Answer 6

I like this question because it is asking for some "good habits". I have found that certain things that are desirable in programming are initially a chore, but become acceptable and even easy once they become habits.

One example is always using smart pointers instead of raw pointers to control heap memory lifetime. Another, related of course, is developing the habit of always using RAII for resource acquisition and release. Another is always using exceptions for error handling. These three tend to simplify code, thereby making it smaller and so faster, as well as easier to understand.

You could also make getters and setters implicitly inline; always make full use of initializer lists in constructors; and always use the find and other related functions that are provided in the std library, instead of crafting your own loops.

Not specifically C++, but it is often worthwhile to avoid data copying. In long-running programs with a lot of memory allocation it can be worthwhile to consider memory allocation as a major part of the design, so that the memory you use comes from pools that are reused, although this is not necessarily a common enough thing to be considered worthy of forming a habit.

One more thing - do not copy code from one place to another if you need the functionality - use a function. This keeps code size small and makes it easier to optimize all the places that use this functionality.