What are the best practices for C++ performance optimization?

To optimize C performance, use these best practices: Use inline functions to increase the efficiency of small functions. Avoid unnecessary copies and use references or pointers instead. Use caching to reduce the overhead of accessing external memory. Optimize containers to improve lookup performance, such as using unordered_map. Avoid using virtual functions to reduce runtime overhead.

C Best Practices for Performance Optimization

Introduction

C is a A high-performance language, but if not optimized, its performance may suffer. Following some best practices can significantly improve the performance of your C code.

1. Use inline functions

Inline functions embed function code directly into the code that calls it, avoiding the overhead of function calls. Inlining is especially effective for small functions.

inline double calculateArea(double radius) {
  return 3.14159265 * radius * radius;
}

2. Avoid unnecessary copies

Unnecessary copies waste time and space. Use references or pointers to reduce the amount of data copied.

void swap(int &a, int &b) {
  int temp = a;
  a = b;
  b = temp;
}

3. Use cache

Cache stores frequently accessed data in fast memory, thereby reducing the overhead of accessing external memory.

int cachedValue = -1;
int getCachedValue() {
  if (cachedValue == -1) {
    cachedValue = calculateValue();
  }
  return cachedValue;
}

4. Optimizing containers

The standard library container provides many options to optimize performance. For example, using unordered_map instead of map can result in faster lookup times.

unordered_map<int, string> myMap;

5. Avoid using virtual functions

Virtual functions cause runtime polymorphism overhead. Only use them when you really need them.

class Base {
 public:
  virtual void print() {
    cout << "Base class" << endl;
  }
};

class Derived : public Base {
 public:
  void print() override {
    cout << "Derived class" << endl;
  }
};

Practical Example

The following is a practical example of optimizing C code using the above best practices:

// 计算圆的面积
inline double calculateArea(double radius) {
  return 3.14159265 * radius * radius;
}

// 避免不必要的拷贝
void swap(int &a, int &b) {
  int temp = a;
  a = b;
  b = temp;
}

// 使用缓存
unordered_map<int, string> myMap;

By applying these best practices, you The performance of C code can be significantly improved, allowing it to handle larger data sets and more complex algorithms.

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