pow()函数和直接用乘法的性能比较——以camel函数为例

#include <iostream>
#include <cmath>
#include <ctime>
#include <vector>
using namespace std;

//Func1：全部用乘法
double Func1(const vector<double> &state)
{
    double x = state[0];
    double y = state[1];
    double f = (4 - 2.1*x*x + x*x*x*x / 3.0)*x*x + x*y + (-4 + 4.0 * y*y)*y*y;
    return  f;
    
}
//Func2：四次幂用pow(),其余用乘法
double Func2(const vector<double> &state)
{
    double x = state[0];
    double y = state[1];
    double f;
    f = (4 - 2.1*x*x + pow(x,4) / 3.0)*x*x + x*y + (-4 + 4.0 * y*y)*y*y;
    return f;
}
//Func3：全部用pow()函数来计算
double Func3(const vector<double> &state)
{
    double x = state[0];
    double y = state[1];
    double f;
    f = (4 - 2.1*pow(x, 2) + pow(x, 4) / 3.0)*pow(x, 2) + x*y + (-4 + 4.0 * pow(y, 2))*pow(y, 2);
    return f;
}

int main()
{
    vector<double> initialState(2);
    initialState[0] = 0.0898;
    initialState[1] = -0.7126;
    
    clock_t start, end;

    //Func1的测试
    int i = 10000000;
    start = clock();
    while (i--)
    {
        Func1(initialState);
    }
    end = clock();
    cout << "Func1 cost: " << (double)(end - start) / CLOCKS_PER_SEC << endl;

    //Func2的测试
    int j = 10000000;
    start = clock();
    while (j--)
    {
        Func2(initialState);
    }
    end = clock();
    cout << "Func2 cost: " << (double)(end - start) / CLOCKS_PER_SEC << endl;

    //Func3的测试
    int k = 10000000;
    start = clock();
    while (k--)
    {
        Func3(initialState);
    }
    end = clock();
    cout << "Func3 cost: " << (double)(end - start) / CLOCKS_PER_SEC << endl;

    getchar();
    return 0;
}