diff options
Diffstat (limited to 'src/math/acoshf.c')
| -rw-r--r-- | src/math/acoshf.c | 47 |
1 files changed, 11 insertions, 36 deletions
diff --git a/src/math/acoshf.c b/src/math/acoshf.c index 0f7aae2a..4596085e 100644 --- a/src/math/acoshf.c +++ b/src/math/acoshf.c @@ -1,42 +1,17 @@ -/* origin: FreeBSD /usr/src/lib/msun/src/e_acoshf.c */ -/* - * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. - */ -/* - * ==================================================== - * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. - * - * Developed at SunPro, a Sun Microsystems, Inc. business. - * Permission to use, copy, modify, and distribute this - * software is freely granted, provided that this notice - * is preserved. - * ==================================================== - */ - #include "libm.h" -static const float -ln2 = 6.9314718246e-01; /* 0x3f317218 */ - +/* acosh(x) = log(x + sqrt(x*x-1)) */ float acoshf(float x) { - float t; - int32_t hx; + union {float f; int32_t i;} u = {.f = x}; - GET_FLOAT_WORD(hx, x); - if (hx < 0x3f800000) { /* x < 1 */ - return (x-x)/(x-x); - } else if (hx >= 0x4d800000) { /* x > 2**28 */ - if (hx >= 0x7f800000) /* x is inf of NaN */ - return x + x; - return logf(x) + ln2; /* acosh(huge)=log(2x) */ - } else if (hx == 0x3f800000) { - return 0.0f; /* acosh(1) = 0 */ - } else if (hx > 0x40000000) { /* 2**28 > x > 2 */ - t = x*x; - return logf(2.0f*x - 1.0f/(x+sqrtf(t-1.0f))); - } else { /* 1 < x < 2 */ - t = x-1.0f; - return log1pf(t + sqrtf(2.0f*t+t*t)); - } + if (u.i < 0x3f800000+(1<<23)) + /* x < 2, invalid if x < 1 or nan */ + /* up to 2ulp error in [1,1.125] */ + return log1pf(x-1 + sqrtf((x-1)*(x-1)+2*(x-1))); + if (u.i < 0x3f800000+(12<<23)) + /* x < 0x1p12 */ + return logf(2*x - 1/(x+sqrtf(x*x-1))); + /* x >= 0x1p12 */ + return logf(x) + 0.693147180559945309417232121458176568f; } |