The efficiency test of polynomial calculation and the efficiency of polynomial calculation _php tutorial

The efficiency test of polynomial calculation and the efficiency of polynomial calculation

Polynomial calculation call library function Pow method and Qin Jiushao algorithm, we can measure the efficiency of their operation

Calculation function f (x) =1+ (σxi/i) (I from 1 to M);

Use the CTime time function to test the run time and bring it into the 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;
}

Run time See table below

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 results of the running time that the Qin Jiushao algorithm is much more efficient than the POW call method

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