快速sin cos

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在优化算法时时间项费非常关键，如果需要大量使用sin cos，那么对sin cos的优化将大大提高运算速度

最近发现一个快速计算sin cos的方法，

#include"cmath"#include<iostream>#include<cstdio>#include<ctime>using namespace std;#define MILLION 1000000////////////////////////////////////////////////////////////////////////////////#define CV_PI 3.14159265359#define halfPi ((float)(CV_PI*0.5))#define Pi     ((float)CV_PI)#define a0  0 /*-4.172325e-7f*/   /*(-(float)0x7)/((float)0x1000000); */#define a1 1.000025f        /*((float)0x1922253)/((float)0x1000000)*2/Pi; */#define a2 -2.652905e-4f    /*(-(float)0x2ae6)/((float)0x1000000)*4/(Pi*Pi); */#define a3 -0.165624f       /*(-(float)0xa45511)/((float)0x1000000)*8/(Pi*Pi*Pi); */#define a4 -1.964532e-3f    /*(-(float)0x30fd3)/((float)0x1000000)*16/(Pi*Pi*Pi*Pi); */#define a5 1.02575e-2f      /*((float)0x191cac)/((float)0x1000000)*32/(Pi*Pi*Pi*Pi*Pi); */#define a6 -9.580378e-4f    /*(-(float)0x3af27)/((float)0x1000000)*64/(Pi*Pi*Pi*Pi*Pi*Pi); */#define _sin(x) ((((((a6*(x) + a5)*(x) + a4)*(x) + a3)*(x) + a2)*(x) + a1)*(x) + a0)#define _cos(x) _sin(halfPi - (x))////////////////////////////////////////////////////////////////////////////////////int main(){    struct timespec tpstart;    struct timespec tpend;    long timedif;//fastsin cos{float sine, cose;float dsin, dcos;clock_gettime(CLOCK_MONOTONIC, &tpstart);for(float ang = 0.0; ang < CV_PI; ang += 0.0001){sine = _sin(ang);cose = _cos(ang);}clock_gettime(CLOCK_MONOTONIC, &tpend);        timedif = MILLION*(tpend.tv_sec-tpstart.tv_sec)+(tpend.tv_nsec-tpstart.tv_nsec)/1000;        printf("it took %ld microseconds\n", timedif);}//sin cos{double sine,cose;clock_gettime(CLOCK_MONOTONIC, &tpstart);for(double ang = 0.0; ang < CV_PI; ang += 0.0001){sine = sin(ang);cose = cos(ang);}clock_gettime(CLOCK_MONOTONIC, &tpend);        timedif = MILLION*(tpend.tv_sec-tpstart.tv_sec)+(tpend.tv_nsec-tpstart.tv_nsec)/1000;        printf("it took %ld microseconds\n", timedif);}return 0;}

Makefile文件

fastsin : fastsin.cppg++ -o fastsin fastsin.cpp -lrtclean:rm -f fastsin

计算结果：

it took 1300 microseconds
it took 6297 microseconds

系统自带的sin cos计算（double），大概是快速sin cos计算（float）时间的5倍。