diff options
Diffstat (limited to 'src/math/acos.c')
| -rw-r--r-- | src/math/acos.c | 74 |
1 files changed, 37 insertions, 37 deletions
diff --git a/src/math/acos.c b/src/math/acos.c index 0eb15bed..be95d25e 100644 --- a/src/math/acos.c +++ b/src/math/acos.c @@ -36,12 +36,8 @@ #include "libm.h" static const double -pi = 3.14159265358979311600e+00, /* 0x400921FB, 0x54442D18 */ -pio2_hi = 1.57079632679489655800e+00; /* 0x3FF921FB, 0x54442D18 */ -// FIXME -static const volatile double -pio2_lo = 6.12323399573676603587e-17; /* 0x3C91A626, 0x33145C07 */ -static const double +pio2_hi = 1.57079632679489655800e+00, /* 0x3FF921FB, 0x54442D18 */ +pio2_lo = 6.12323399573676603587e-17, /* 0x3C91A626, 0x33145C07 */ pS0 = 1.66666666666666657415e-01, /* 0x3FC55555, 0x55555555 */ pS1 = -3.25565818622400915405e-01, /* 0xBFD4D612, 0x03EB6F7D */ pS2 = 2.01212532134862925881e-01, /* 0x3FC9C155, 0x0E884455 */ @@ -53,49 +49,53 @@ qS2 = 2.02094576023350569471e+00, /* 0x40002AE5, 0x9C598AC8 */ qS3 = -6.88283971605453293030e-01, /* 0xBFE6066C, 0x1B8D0159 */ qS4 = 7.70381505559019352791e-02; /* 0x3FB3B8C5, 0xB12E9282 */ +static double R(double z) +{ + double p, q; + p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); + q = 1.0+z*(qS1+z*(qS2+z*(qS3+z*qS4))); + return p/q; +} + double acos(double x) { - double z,p,q,r,w,s,c,df; - int32_t hx,ix; + double z,w,s,c,df; + uint32_t hx,ix; GET_HIGH_WORD(hx, x); ix = hx & 0x7fffffff; - if (ix >= 0x3ff00000) { /* |x| >= 1 */ + /* |x| >= 1 or nan */ + if (ix >= 0x3ff00000) { uint32_t lx; GET_LOW_WORD(lx,x); - if ((ix-0x3ff00000 | lx) == 0) { /* |x|==1 */ - if (hx > 0) return 0.0; /* acos(1) = 0 */ - return pi + 2.0*pio2_lo; /* acos(-1)= pi */ + if ((ix-0x3ff00000 | lx) == 0) { + /* acos(1)=0, acos(-1)=pi */ + if (hx >> 31) + return 2*pio2_hi + 0x1p-1000; + return 0; } - return (x-x)/(x-x); /* acos(|x|>1) is NaN */ + return 0/(x-x); } - if (ix < 0x3fe00000) { /* |x| < 0.5 */ + /* |x| < 0.5 */ + if (ix < 0x3fe00000) { if (ix <= 0x3c600000) /* |x| < 2**-57 */ - return pio2_hi + pio2_lo; - z = x*x; - p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); - q = 1.0+z*(qS1+z*(qS2+z*(qS3+z*qS4))); - r = p/q; - return pio2_hi - (x - (pio2_lo-x*r)); - } else if (hx < 0) { /* x < -0.5 */ + return pio2_hi + 0x1p-1000; + return pio2_hi - (x - (pio2_lo-x*R(x*x))); + } + /* x < -0.5 */ + if (hx >> 31) { z = (1.0+x)*0.5; - p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); - q = 1.0+z*(qS1+z*(qS2+z*(qS3+z*qS4))); - s = sqrt(z); - r = p/q; - w = r*s-pio2_lo; - return pi - 2.0*(s+w); - } else { /* x > 0.5 */ - z = (1.0-x)*0.5; s = sqrt(z); - df = s; - SET_LOW_WORD(df,0); - c = (z-df*df)/(s+df); - p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); - q = 1.0+z*(qS1+z*(qS2+z*(qS3+z*qS4))); - r = p/q; - w = r*s+c; - return 2.0*(df+w); + w = R(z)*s-pio2_lo; + return 2*(pio2_hi - (s+w)); } + /* x > 0.5 */ + z = (1.0-x)*0.5; + s = sqrt(z); + df = s; + SET_LOW_WORD(df,0); + c = (z-df*df)/(s+df); + w = R(z)*s+c; + return 2*(df+w); } |