12 Way to optimize C++ Code

C++ Code optimizations

To optimize you c++ code you can do the steps shown bellow, it will make your code more fast and optimized.

1. Use Initialization Lists

Always use initialization lists in constructors. For example, use

TMyClass::TMyClass(const TData &data) : m_Data(data)
{
}

Rather than 

TMyClass::TMyClass(const TData &data)
{m_Data = data;
}

Without initialization lists, the variable's default constructor is invoked behind-the-scenes prior to the class's constructor, then its assignment operator is invoked. With initialization lists, only the copy constructor is invoked.

2. Use 'int'

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

3. Optimize For Loops

Wherever possible, count down to zero rather than up to n. For example, use

for (i = n-1; i >= 0; --i)

Rather than

for (i = 0; i < n; ++i)

The test is done every iteration and it's faster to test against zero than anything else. Note also that

++i is faster than i++ 

when it appears in the third part of the for loop statement.

4. 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.

5. Optimize Switch Statements

Put the most common cases first.

6. Optimize If Statements

Factor out jumps. For example, use

bar();
if (condition)
{undoBar();foo();
} rather than
 if (condition)
{foo();
}
else
{bar();
}

Use a profiler and good judgement to decide if undoing the bar() operation is faster than jumping.

7. Initialize on Declaration

Wherever possible, initialize variables at the time they're declared. For example,

TMyClass x = data;is faster than

TMyClass x;x = data;

Declaration then initialization invokes the object's default constructor then its assignment operator. Initializing in the declaration invokes only its copy constructor.

8. Pass By Reference

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

void foo(TMyClass &x)

Rather than

void foo(TMyClass x)

9. Avoid Expensive Operations

Addition is cheaper than multiplication and multiplication is cheaper than division. Factor out expensive operations wherever possible.

10. Delay Variable Declarations

Leave variable declarations right until the point when they're needed. Remember that when a variable is declared its constructor is called. This is wasteful if the variable is not used in the current scope.

Use 'op=' Wherever possible, use 'op=' in favour of 'op'. For example, use
 x += value;

Rather than

x = x + value;

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

11. Use Nameless Objects

Wherever possible, use nameless objects. For example,

foo(TMyClass("abc"));

is faster than

TMyClass x("abc");foo(x); 

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

12. 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.

This is a 12 way to optimize c++ code and improve programs.

I hope it will help you improving your code you can ask and i will try to reply as soon as possible.