| /* |
| * Copyright (c) 2014 Advanced Micro Devices, Inc. |
| * |
| * Permission is hereby granted, free of charge, to any person obtaining a copy |
| * of this software and associated documentation files (the "Software"), to deal |
| * in the Software without restriction, including without limitation the rights |
| * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
| * copies of the Software, and to permit persons to whom the Software is |
| * furnished to do so, subject to the following conditions: |
| * |
| * The above copyright notice and this permission notice shall be included in |
| * all copies or substantial portions of the Software. |
| * |
| * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
| * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
| * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN |
| * THE SOFTWARE. |
| */ |
| |
| #include "math64.h" |
| #include "ep_logD.h" |
| |
| __attribute__((overloadable)) double |
| acosh(double x) |
| { |
| const double recrteps = 0x1.6a09e667f3bcdp+26; // 1/sqrt(eps) = 9.49062656242515593767e+07 |
| //log2_lead and log2_tail sum to an extra-precise version of log(2) |
| const double log2_lead = 0x1.62e42ep-1; |
| const double log2_tail = 0x1.efa39ef35793cp-25; |
| |
| // Handle x >= 128 here |
| int xlarge = x > recrteps; |
| double r = x + sqrt(fma(x, x, -1.0)); |
| r = xlarge ? x : r; |
| |
| int xexp; |
| double r1, r2; |
| ep_log(r, &xexp, &r1, &r2); |
| |
| double dxexp = xexp + xlarge; |
| r1 = fma(dxexp, log2_lead, r1); |
| r2 = fma(dxexp, log2_tail, r2); |
| |
| double ret1 = r1 + r2; |
| |
| // Handle 1 < x < 128 here |
| // We compute the value |
| // t = x - 1.0 + sqrt(2.0*(x - 1.0) + (x - 1.0)*(x - 1.0)) |
| // using simulated quad precision. |
| double t = x - 1.0; |
| double u1 = t * 2.0; |
| |
| // (t,0) * (t,0) -> (v1, v2) |
| double v1 = t * t; |
| double v2 = fma(t, t, -v1); |
| |
| // (u1,0) + (v1,v2) -> (w1,w2) |
| r = u1 + v1; |
| double s = (((u1 - r) + v1) + v2); |
| double w1 = r + s; |
| double w2 = (r - w1) + s; |
| |
| // sqrt(w1,w2) -> (u1,u2) |
| double p1 = sqrt(w1); |
| double a1 = p1*p1; |
| double a2 = fma(p1, p1, -a1); |
| double temp = (((w1 - a1) - a2) + w2); |
| double p2 = MATH_DIVIDE(temp * 0.5, p1); |
| u1 = p1 + p2; |
| double u2 = (p1 - u1) + p2; |
| |
| // (u1,u2) + (t,0) -> (r1,r2) |
| r = u1 + t; |
| s = ((u1 - r) + t) + u2; |
| // r1 = r + s; |
| // r2 = (r - r1) + s; |
| // t = r1 + r2; |
| t = r + s; |
| |
| // For arguments 1.13 <= x <= 1.5 the log1p function is good enough |
| double ret2 = log1p(t); |
| |
| ulong ux = as_ulong(x); |
| double ret = x >= 128.0 ? ret1 : ret2; |
| |
| ret = ux >= 0x7FF0000000000000 ? x : ret; |
| ret = x == 1.0 ? 0.0 : ret; |
| ret = (ux & SIGNBIT_DP64) != 0UL | x < 1.0 ? as_double(QNANBITPATT_DP64) : ret; |
| |
| return ret; |
| } |