| /* origin: FreeBSD /usr/src/lib/msun/src/s_csqrtf.c */ |
| /*- |
| * Copyright (c) 2007 David Schultz <das@FreeBSD.ORG> |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND |
| * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE |
| * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| * SUCH DAMAGE. |
| */ |
| |
| #include "complex_impl.h" |
| |
| /* |
| * gcc doesn't implement complex multiplication or division correctly, |
| * so we need to handle infinities specially. We turn on this pragma to |
| * notify conforming c99 compilers that the fast-but-incorrect code that |
| * gcc generates is acceptable, since the special cases have already been |
| * handled. |
| */ |
| #pragma STDC CX_LIMITED_RANGE ON |
| |
| float complex csqrtf(float complex z) |
| { |
| float a = crealf(z), b = cimagf(z); |
| double t; |
| |
| /* Handle special cases. */ |
| if (z == 0) |
| return CMPLXF(0, b); |
| if (isinf(b)) |
| return CMPLXF(INFINITY, b); |
| if (isnan(a)) { |
| t = (b - b) / (b - b); /* raise invalid if b is not a NaN */ |
| return CMPLXF(a, t); /* return NaN + NaN i */ |
| } |
| if (isinf(a)) { |
| /* |
| * csqrtf(inf + NaN i) = inf + NaN i |
| * csqrtf(inf + y i) = inf + 0 i |
| * csqrtf(-inf + NaN i) = NaN +- inf i |
| * csqrtf(-inf + y i) = 0 + inf i |
| */ |
| if (signbit(a)) |
| return CMPLXF(fabsf(b - b), copysignf(a, b)); |
| else |
| return CMPLXF(a, copysignf(b - b, b)); |
| } |
| /* |
| * The remaining special case (b is NaN) is handled just fine by |
| * the normal code path below. |
| */ |
| |
| /* |
| * We compute t in double precision to avoid overflow and to |
| * provide correct rounding in nearly all cases. |
| * This is Algorithm 312, CACM vol 10, Oct 1967. |
| */ |
| if (a >= 0) { |
| t = sqrt((a + hypot(a, b)) * 0.5); |
| return CMPLXF(t, b / (2.0 * t)); |
| } else { |
| t = sqrt((-a + hypot(a, b)) * 0.5); |
| return CMPLXF(fabsf(b) / (2.0 * t), copysignf(t, b)); |
| } |
| } |