Efficiency Test for Polynomial Calculations

Polynomial calculation calls the library function pow method and Qin Jiutao algorithm. Let’s measure their operating efficiency

Calculation function f(x)=1+(Σxⁱ/i)(i is taken from 1 to m);

Use the ctime time function to test the running time, and bring x=0.9 to calculate

#include
#include;
#include
using namespace std;
double Fn1(double x);
double Fn2(double x);
#define m 1000000000
clock_t start, stop;
int main(){
double x;
x = 0.9;
start = clock();
cout << Fn1(x) << endl;
stop = clock();
cout << double(stop - start) / CLK_TCK << endl;
//------------- ---------------------
start = clock();
cout << Fn2(x) << endl;
stop = clock() ;
cout << double(stop - start) / CLK_TCK << endl;
return 0;
}
double Fn1(double x){
int i;
double f=1.0;
for (i = 1; i <= m; i++)
f += pow(x, i)/i;
return f;
}
double Fn2(double x){
int i;
double f = 0.0;
for ( i = m; i >= 1; i--) /*Qin Jiuchao polynomial algorithm*/
f = f*x + 1.0 / i;
return f*x + 1.0;
}

See the table below for the running time

m	100	1000	10000	100000	1000000	10000000	1000000	1000000000
Fn1	0.001	0.001	0.003	0.015	0.157	1.619	17.955	191.608
Fn2	0	0	0	0.001	0.005	0.0 49	0.472	4.706

It can be seen from the running time results , Qin Jiushao algorithm is much more efficient than the pow calling method

The above has introduced the efficiency test of polynomial calculations, including aspects of it. I hope it will be helpful to friends who are interested in PHP tutorials.