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Efficiency Test for Polynomial Calculations

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Release: 2016-07-30 13:32:01
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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.

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