[C/C++] - C++ optimizations (general)

1- Use 'int'

Always use the int data type instead of char or short wherever possible. int is always the native type for the machine.

2- Make Local Functions Static

Always declare local functions as static, e.g.,

static void foo()

This means they will not be visible to functions outside the .cpp file, and some C++ compilers can take advantage of this in their optimizations.

3- Avoid Expensive Operations

Addition is faster than multiplication and multiplication is faster than division. Factor out expensive operations whereever possible.

4- Pass By Reference

Always try to pass classes by reference rather than by value. For example, use

void foo(TMyClass &myClass)

rather than

void foo(TMyClass myClass)

5- Use 'op='

Wherever possible, use 'op=' in favour of 'op'. For example, use

myClass += value;

rather than

myClass = myClass + value;

The first version is better than the second because it avoids creating a temporary object.

6- Inline Small Functions

Small, performance critical functions should be inlined using the inline keyword, e.g.,

inline void foo()

This causes the compiler to duplicate the body of the function in the place it was called from. Inlining large functions can cause cache misses resulting in slower execution times.

7- Use Nameless Classes

Whereever possible, use nameless classes. For example,

foo(TMyClass("abc"));

is faster than

TMyClass myClass("abc");

foo(myClass);

because, in the first case, the parameter and the class share memory.