Aren/toaruos
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

aarch64: atan2() by polynomial approximation

Browse Source
This commit is contained in:
K. Lange 2022-04-13 13:56:50 -07:00
parent 33d7c46a44
commit e20689f1d8
1 changed files with 25 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

25
libc/arch/aarch64/bad.c
View File

@ -10,7 +10,32 @@ double tan(double theta) {
return sin(theta) / cos(theta);
}
/**
* Polynomial approximation of arctangent
*
* @see https://www.dsprelated.com/showarticle/1052.php
*/
static inline double _atan(double z) {;
double n1 = 0.97239411;
double n2 = -0.19194795;
return (n1 + n2 * z * z) * z;
}
double atan2(double y, double x) {
if (x != 0.0) {
if (fabs(x) > fabs(y)) {
double z = y / x;
if (x > 0.0) return _atan(z);
else if (y >= 0.0) return _atan(z) + M_PI;
else return _atan(z) - M_PI;
} else {
double z = x / y;
if (y > 0.0) return -_atan(z) + M_PI/2.0;
else return -_atan(z) - M_PI/2.0;
}
} else {
if (y > 0.0) return M_PI/2.0;
else if (y < 0.0) return -M_PI/2.0;
}
return 0.0;
}