Efficiency test of polynomial calculation, polynomial calculation efficiency_PHP tutorial

Efficiency test of polynomial calculation, polynomial calculation efficiency

Polynomial calculation calls the library function pow method and Qin Jiushao algorithm, let’s measure their operating efficiency

Calculate 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 in 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 Jiushao polynomial algorithm*/
f = f*x 1.0 / i;
return f*x 1.0;
}

See the table below for 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	0.049	0.472	4.706

It can be seen from the running time results that the efficiency of Qin Jiushao's algorithm is much higher than that of the pow calling method

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