diff options
Diffstat (limited to 'sysdeps/libm-ieee754/s_csqrtl.c')
| -rw-r--r-- | sysdeps/libm-ieee754/s_csqrtl.c | 31 |
1 files changed, 17 insertions, 14 deletions
diff --git a/sysdeps/libm-ieee754/s_csqrtl.c b/sysdeps/libm-ieee754/s_csqrtl.c index b772709947..4b7ed983d8 100644 --- a/sysdeps/libm-ieee754/s_csqrtl.c +++ b/sysdeps/libm-ieee754/s_csqrtl.c @@ -1,5 +1,5 @@ /* Complex square root of long double value. - Copyright (C) 1997 Free Software Foundation, Inc. + Copyright (C) 1997, 1998 Free Software Foundation, Inc. This file is part of the GNU C Library. Based on an algorithm by Stephen L. Moshier <moshier@world.std.com>. Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997. @@ -84,22 +84,25 @@ __csqrtl (__complex__ long double x) } else { -#if 0 /* FIXME: this is broken. */ - __complex__ long double q; - long double t, r; +#if 0 + long double d, r, s; - if (fabsl (__imag__ x) < 2.0e-4 * fabsl (__real__ x)) - t = 0.25 * __imag__ x * (__imag__ x / __real__ x); + d = __ieee754_hypotl (__real__ x, __imag__ x); + /* Use the identity 2 Re res Im res = Im x + to avoid cancellation error in d +/- Re x. */ + if (__real__ x > 0) + { + r = __ieee754_sqrtl (0.5L * d + 0.5L * __real__ x); + s = (0.5L * __imag__ x) / r; + } else - t = 0.5 * (__ieee754_hypotl (__real__ x, __imag__ x) - __real__ x); - - r = __ieee754_sqrtl (t); - - __real__ q = __imag__ x / (2.0 * r); - __imag__ q = r; + { + s = __ieee754_sqrtl (0.5L * d - 0.5L * __real__ x); + r = (0.5L * __imag__ x) / s; + } - /* Heron iteration in complex arithmetic. */ - res = 0.5 * (q + q / x); + __real__ res = r; + __imag__ res = __copysignl (s, __imag__ x); #else long double d, imag; |