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C Function call optimization strategy includes: 1. Parameter passing: passing by reference to modify the original value; 2. const parameters: preventing parameter modification and copying; 3. Return value: returning a large data structure by reference, saving copy overhead ;4. Return rvalue reference to avoid unnecessary copying. Through these strategies, function call performance can be optimized and program efficiency improved.
In C programming, function calls are a common part of program execution. Optimizing function calls can improve the overall performance of the program. This article will introduce several parameter passing and return value optimization strategies and demonstrate them with code examples.
When you need to modify the parameter value in the function, using pass by reference can avoid parameter copy overhead, for example:
void Swap(int& a, int& b) { int temp = a; a = b; b = temp; }
is a function Parameter declaration as const
can prevent the function from modifying the parameter value and avoid unnecessary copying, for example:
int Max(const int& a, const int& b) { return a > b ? a : b; }
For large data structures, returning by reference can save copy overhead, for example:
std::vector<int>& GetVector() { static std::vector<int> v = {1, 2, 3}; return v; }
For instant creation and no longer used Objects can avoid unnecessary copying, for example:
std::string Concatenate(const std::string& a, const std::string& b) { return a + b; }
#include <iostream> void OptimizedSwap(int& a, int& b) { a ^= b; b ^= a; a ^= b; } int main() { int x = 1, y = 2; OptimizedSwap(x, y); std::cout << "x: " << x << ", y: " << y << std::endl; // 输出: x: 2, y: 1 return 0; }
In this example, OptimizedSwap
function Use bitwise operations to swap the values of two integers, avoiding the overhead of variable copying.
#include <iostream> std::vector<int>& OptimizedGetVector() { static std::vector<int> v = {1, 2, 3}; return v; } int main() { auto& v = GetVector(); // 按引用获得 vector v.push_back(4); for (int i : v) { std::cout << i << " "; // 输出: 1 2 3 4 } std::cout << std::endl; return 0; }
In this example, the OptimizedGetVector
function returns a std::vector
by reference, avoiding the overhead of creating a new vector. .
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