Macros
#define	PRECISION 9

#define	M_PI 3.141592653589793238462643

Functions
double	sin (double x)

Variables
static double	sin_off_tbl [] = {0.0, -M_PI/2., 0, -M_PI/2.}

static double	sin_sign_tbl [] = {1,-1,-1,1}

Macro Definition Documentation

◆ M_PI

#define M_PI 3.141592653589793238462643

Definition at line 15 of file sin.c.

◆ PRECISION

#define PRECISION 9

Definition at line 14 of file sin.c.

Function Documentation

◆ sin()

double sin ( double x )

Definition at line 21 of file sin.c.

 {
     int quadrant;
     double x2, result;
 
     /* Calculate the quadrant */
     quadrant = (int)(x * (2./M_PI));
 
     /* Get offset inside quadrant */
     x = x - quadrant * (M_PI/2.);
 
     /* Normalize quadrant to [0..3] */
     quadrant = (quadrant - 1) & 0x3;
 
     /* Fixup value for the generic function */
     x += sin_off_tbl[quadrant];
 
     /* Calculate the negative of the square of x */
     x2 = - (x * x);
 
     /* This is an unrolled taylor series using <PRECISION> iterations
      * Example with 4 iterations:
      * result = 1 - x^2/2! + x^4/4! - x^6/6! + x^8/8!
      * To save multiplications and to keep the precision high, it's performed
      * like this:
      * result = 1 - x^2 * (1/2! - x^2 * (1/4! - x^2 * (1/6! - x^2 * (1/8!))))
      */
 
     /* Start with 0, compiler will optimize this away */
     result = 0;
 
 #if (PRECISION >= 10)
     result += 1./(1.*2*3*4*5*6*7*8*9*10*11*12*13*14*15*16*17*18*19*20);
     result *= x2;
 #endif
 #if (PRECISION >= 9)
     result += 1./(1.*2*3*4*5*6*7*8*9*10*11*12*13*14*15*16*17*18);
     result *= x2;
 #endif
 #if (PRECISION >= 8)
     result += 1./(1.*2*3*4*5*6*7*8*9*10*11*12*13*14*15*16);
     result *= x2;
 #endif
 #if (PRECISION >= 7)
     result += 1./(1.*2*3*4*5*6*7*8*9*10*11*12*13*14);
     result *= x2;
 #endif
 #if (PRECISION >= 6)
     result += 1./(1.*2*3*4*5*6*7*8*9*10*11*12);
     result *= x2;
 #endif
 #if (PRECISION >= 5)
     result += 1./(1.*2*3*4*5*6*7*8*9*10);
     result *= x2;
 #endif
     result += 1./(1.*2*3*4*5*6*7*8);
     result *= x2;
 
     result += 1./(1.*2*3*4*5*6);
     result *= x2;
 
     result += 1./(1.*2*3*4);
     result *= x2;
 
     result += 1./(1.*2);
     result *= x2;
 
     result += 1;
 
     /* Apply correct sign */
     result *= sin_sign_tbl[quadrant];
 
     return result;
 }

Variable Documentation

◆ sin_off_tbl

double sin_off_tbl[] = {0.0, -M_PI/2., 0, -M_PI/2.}

static

Definition at line 17 of file sin.c.

Referenced by sin().

◆ sin_sign_tbl

double sin_sign_tbl[] = {1,-1,-1,1}