Rich Felker | b69f695 | 2012-03-13 01:17:53 -0400 | [diff] [blame] | 1 | #include "libm.h" |
| 2 | |
Szabolcs Nagy | f143458 | 2012-12-16 19:49:55 +0100 | [diff] [blame] | 3 | /* sinh(x) = (exp(x) - 1/exp(x))/2 |
| 4 | * = (exp(x)-1 + (exp(x)-1)/exp(x))/2 |
| 5 | * = x + x^3/6 + o(x^5) |
| 6 | */ |
Rich Felker | b69f695 | 2012-03-13 01:17:53 -0400 | [diff] [blame] | 7 | double sinh(double x) |
| 8 | { |
Szabolcs Nagy | f143458 | 2012-12-16 19:49:55 +0100 | [diff] [blame] | 9 | union {double f; uint64_t i;} u = {.f = x}; |
| 10 | uint32_t w; |
| 11 | double t, h, absx; |
Rich Felker | b69f695 | 2012-03-13 01:17:53 -0400 | [diff] [blame] | 12 | |
| 13 | h = 0.5; |
Szabolcs Nagy | f143458 | 2012-12-16 19:49:55 +0100 | [diff] [blame] | 14 | if (u.i >> 63) |
| 15 | h = -h; |
| 16 | /* |x| */ |
| 17 | u.i &= (uint64_t)-1/2; |
| 18 | absx = u.f; |
| 19 | w = u.i >> 32; |
| 20 | |
| 21 | /* |x| < log(DBL_MAX) */ |
| 22 | if (w < 0x40862e42) { |
| 23 | t = expm1(absx); |
| 24 | if (w < 0x3ff00000) { |
| 25 | if (w < 0x3ff00000 - (26<<20)) |
Szabolcs Nagy | c599f4f | 2013-08-15 10:14:46 +0000 | [diff] [blame] | 26 | /* note: inexact and underflow are raised by expm1 */ |
| 27 | /* note: this branch avoids spurious underflow */ |
Rich Felker | b69f695 | 2012-03-13 01:17:53 -0400 | [diff] [blame] | 28 | return x; |
Szabolcs Nagy | f143458 | 2012-12-16 19:49:55 +0100 | [diff] [blame] | 29 | return h*(2*t - t*t/(t+1)); |
| 30 | } |
| 31 | /* note: |x|>log(0x1p26)+eps could be just h*exp(x) */ |
| 32 | return h*(t + t/(t+1)); |
Rich Felker | b69f695 | 2012-03-13 01:17:53 -0400 | [diff] [blame] | 33 | } |
| 34 | |
Szabolcs Nagy | f143458 | 2012-12-16 19:49:55 +0100 | [diff] [blame] | 35 | /* |x| > log(DBL_MAX) or nan */ |
| 36 | /* note: the result is stored to handle overflow */ |
| 37 | t = 2*h*__expo2(absx); |
| 38 | return t; |
Rich Felker | b69f695 | 2012-03-13 01:17:53 -0400 | [diff] [blame] | 39 | } |