diff options
Diffstat (limited to 'lib/msun/src/e_lgamma_r.c')
| -rw-r--r-- | lib/msun/src/e_lgamma_r.c | 64 |
1 files changed, 31 insertions, 33 deletions
diff --git a/lib/msun/src/e_lgamma_r.c b/lib/msun/src/e_lgamma_r.c index 1cff592..7a95ea4 100644 --- a/lib/msun/src/e_lgamma_r.c +++ b/lib/msun/src/e_lgamma_r.c @@ -86,8 +86,10 @@ __FBSDID("$FreeBSD$"); #include "math.h" #include "math_private.h" +static const volatile double vzero = 0; + static const double -two52= 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */ +zero= 0.00000000000000000000e+00, half= 5.00000000000000000000e-01, /* 0x3FE00000, 0x00000000 */ one = 1.00000000000000000000e+00, /* 0x3FF00000, 0x00000000 */ pi = 3.14159265358979311600e+00, /* 0x400921FB, 0x54442D18 */ @@ -154,39 +156,35 @@ w4 = -5.95187557450339963135e-04, /* 0xBF4380CB, 0x8C0FE741 */ w5 = 8.36339918996282139126e-04, /* 0x3F4B67BA, 0x4CDAD5D1 */ w6 = -1.63092934096575273989e-03; /* 0xBF5AB89D, 0x0B9E43E4 */ -static const double zero= 0.00000000000000000000e+00; - - static double sin_pi(double x) +/* + * Compute sin(pi*x) without actually doing the pi*x multiplication. + * sin_pi(x) is only called for x < 0 and |x| < 2**(p-1) where p is + * the precision of x. + */ +static double +sin_pi(double x) { + volatile double vz; double y,z; - int n,ix; + int n; + + y = -x; - GET_HIGH_WORD(ix,x); - ix &= 0x7fffffff; + vz = y+0x1p52; /* depend on 0 <= y < 0x1p52 */ + z = vz-0x1p52; /* rint(y) for the above range */ + if (z == y) + return zero; - if(ix<0x3fd00000) return __kernel_sin(pi*x,zero,0); - y = -x; /* x is assume negative */ + vz = y+0x1p50; + GET_LOW_WORD(n,vz); /* bits for rounded y (units 0.25) */ + z = vz-0x1p50; /* y rounded to a multiple of 0.25 */ + if (z > y) { + z -= 0.25; /* adjust to round down */ + n--; + } + n &= 7; /* octant of y mod 2 */ + y = y - z + n * 0.25; /* y mod 2 */ - /* - * argument reduction, make sure inexact flag not raised if input - * is an integer - */ - z = floor(y); - if(z!=y) { /* inexact anyway */ - y *= 0.5; - y = 2.0*(y - floor(y)); /* y = |x| mod 2.0 */ - n = (int) (y*4.0); - } else { - if(ix>=0x43400000) { - y = zero; n = 0; /* y must be even */ - } else { - if(ix<0x43300000) z = y+two52; /* exact */ - GET_LOW_WORD(n,z); - n &= 1; - y = n; - n<<= 2; - } - } switch (n) { case 0: y = __kernel_sin(pi*y,zero,0); break; case 1: @@ -206,7 +204,7 @@ __ieee754_lgamma_r(double x, int *signgamp) { double t,y,z,nadj,p,p1,p2,p3,q,r,w; int32_t hx; - int i,lx,ix; + int i,ix,lx; EXTRACT_WORDS(hx,lx,x); @@ -214,7 +212,7 @@ __ieee754_lgamma_r(double x, int *signgamp) *signgamp = 1; ix = hx&0x7fffffff; if(ix>=0x7ff00000) return x*x; - if((ix|lx)==0) return one/zero; + if((ix|lx)==0) return one/vzero; if(ix<0x3b900000) { /* |x|<2**-70, return -log(|x|) */ if(hx<0) { *signgamp = -1; @@ -223,9 +221,9 @@ __ieee754_lgamma_r(double x, int *signgamp) } if(hx<0) { if(ix>=0x43300000) /* |x|>=2**52, must be -integer */ - return one/zero; + return one/vzero; t = sin_pi(x); - if(t==zero) return one/zero; /* -integer */ + if(t==zero) return one/vzero; /* -integer */ nadj = __ieee754_log(pi/fabs(t*x)); if(t<zero) *signgamp = -1; x = -x; |
