Breaking through the bottleneck of C++ template programming

The bottleneck of C++ template programming is mainly caused by template instantiation expansion and calculation during compilation. Solutions include: 1. Metaprogramming: perform calculations and operations at compile time; 2. Expression templates: perform expressions at compile time; 3. Lateral thinking: avoid instantiation and computation during compile time, use runtime polymorphism or functions pointer. By employing these techniques, compilation time and code size can be significantly reduced, and application performance improved.

C++ Template Programming Bottleneck Breakthrough

Template programming is a powerful tool in C++ for writing reusable, type-safe code. However, when templates become complex, compilation time and code size increase rapidly, resulting in performance losses.

Problem

The bottleneck in template programming mainly stems from the following reasons:

• Template instantiation inflation (TI): The template is instantiated Casting to every possible type results in code bloat and increased compilation time.
• Compile Time Calculation (CTE): Calculations in templates are performed at compile time, increasing compilation time.

Solution

mengatasi The methods for these bottlenecks are:

• Metaprogramming (MP): Use template metaprogramming technology Calculations and operations are performed at compile time, using the compiler to optimize the code.
• Expression Template (ET): A special template that allows expressions to be executed at compile time, thus avoiding CTEs.
• Lateral Thinking (LF): A programming paradigm that focuses on avoiding instantiation and CTEs, through the use of runtime polymorphism or function pointers.

Practical case

Consider the following code, in which function max uses templates for generalization:

template <typename T>
T max(T a, T b) {
  return a > b ? a : b;
}

This implementation will be performed in each The template is instantiated when called, resulting in TI.

Using MP and ET:

template <typename T>
constexpr T max(T a, T b) {
  return a > b ? a : b;
}

By using the constexpr keyword, this calculation is now performed at compile time, reducing TI and CTE.

Using LF:

struct Max {
  template <typename T>
  static T apply(T a, T b) {
    return a > b ? a : b;
  }
}

// 使用：
auto result = Max::apply<double>(1.2, 3.4);

Using runtime polymorphism, this implementation avoids instantiation and CTEs.

Conclusion

By utilizing technologies such as MP, ET and LF, the bottleneck of C++ template programming can be broken. This will significantly reduce compilation time and code size, thereby improving application performance.

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