How to consider performance optimization in C++ class design?

Tips to improve performance in C++ class design include: avoiding unnecessary copying, optimizing data layout, and using constexpr. Practical case: Use object pool to optimize object creation and destruction.

Performance optimization in C++ class design

It is important to consider performance optimization when designing classes in C++, which can improve the code efficiency and reduce runtime overhead. Here are some practical tips to improve performance:

Avoid unnecessary copies

When you copy a class object, the compiler allocates new memory and copies all data members. This creates additional overhead when dealing with large objects. Copying can be avoided by using references or pointers as follows:

class MyClass {
public:
  // 构造函数
  MyClass(int* data) : data_(data) {}

  // 获取 data 而不复制
  int* GetData() { return data_; }

private:
  int* data_; // 指针指向外部数据，避免复制
};

Optimize data layout

Member variables of a class should be ordered by frequency of access. The most frequently accessed members should be placed first to reduce cache misses. For example, if the name field in a structure is more commonly used than the ID field, it can be arranged as follows: Constants can use the

constexpr

keyword to optimize their performance. constexpr Functions and variables can be evaluated at compile time, eliminating runtime overhead. For example:

struct Person {
  string name;
  int id;
};

Practical case: Object poolIn scenarios where a large number of objects need to be frequently created and destroyed, the object pool can optimize performance. Object pools pre-allocate a set of objects and allocate objects from them when needed. This eliminates the overhead of dynamic memory allocation and deallocation each time a new object is created.

constexpr int GetMax() { return 100; }

int main() {
  const int max = GetMax(); // 编译时计算
  // ...
}

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