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Diffstat (limited to 'sysdeps/libm-ieee754/e_expf.c')
| -rw-r--r-- | sysdeps/libm-ieee754/e_expf.c | 140 |
1 files changed, 0 insertions, 140 deletions
diff --git a/sysdeps/libm-ieee754/e_expf.c b/sysdeps/libm-ieee754/e_expf.c deleted file mode 100644 index e8a9c9d874..0000000000 --- a/sysdeps/libm-ieee754/e_expf.c +++ /dev/null @@ -1,140 +0,0 @@ -/* Single-precision floating point e^x. - Copyright (C) 1997, 1998 Free Software Foundation, Inc. - This file is part of the GNU C Library. - Contributed by Geoffrey Keating <geoffk@ozemail.com.au> - - The GNU C Library is free software; you can redistribute it and/or - modify it under the terms of the GNU Library General Public License as - published by the Free Software Foundation; either version 2 of the - License, or (at your option) any later version. - - The GNU C Library is distributed in the hope that it will be useful, - but WITHOUT ANY WARRANTY; without even the implied warranty of - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU - Library General Public License for more details. - - You should have received a copy of the GNU Library General Public - License along with the GNU C Library; see the file COPYING.LIB. If not, - write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, - Boston, MA 02111-1307, USA. */ - -/* How this works: - - The input value, x, is written as - - x = n * ln(2) + t/512 + delta[t] + x; - - where: - - n is an integer, 127 >= n >= -150; - - t is an integer, 177 >= t >= -177 - - delta is based on a table entry, delta[t] < 2^-28 - - x is whatever is left, |x| < 2^-10 - - Then e^x is approximated as - - e^x = 2^n ( e^(t/512 + delta[t]) - + ( e^(t/512 + delta[t]) - * ( p(x + delta[t] + n * ln(2)) - delta ) ) ) - - where - - p(x) is a polynomial approximating e(x)-1; - - e^(t/512 + delta[t]) is obtained from a table. - - The table used is the same one as for the double precision version; - since we have the table, we might as well use it. - - It turns out to be faster to do calculations in double precision than - to perform an 'accurate table method' expf, because of the range reduction - overhead (compare exp2f). - */ -#ifndef _GNU_SOURCE -#define _GNU_SOURCE -#endif -#include <float.h> -#include <ieee754.h> -#include <math.h> -#include <fenv.h> -#include <inttypes.h> -#include <math_private.h> - -extern const float __exp_deltatable[178]; -extern const double __exp_atable[355] /* __attribute__((mode(DF))) */; - -static const volatile float TWOM100 = 7.88860905e-31; -static const volatile float TWO127 = 1.7014118346e+38; - -float -__ieee754_expf (float x) -{ - static const float himark = 88.72283935546875; - static const float lomark = -103.972084045410; - /* Check for usual case. */ - if (isless (x, himark) && isgreater (x, lomark)) - { - static const float THREEp42 = 13194139533312.0; - static const float THREEp22 = 12582912.0; - /* 1/ln(2). */ -#undef M_1_LN2 - static const float M_1_LN2 = 1.44269502163f; - /* ln(2) */ -#undef M_LN2 - static const double M_LN2 = .6931471805599452862; - - int tval; - double x22, t, result, dx; - float n, delta; - union ieee754_double ex2_u; - fenv_t oldenv; - - feholdexcept (&oldenv); -#ifdef FE_TONEAREST - fesetround (FE_TONEAREST); -#endif - - /* Calculate n. */ - n = x * M_1_LN2 + THREEp22; - n -= THREEp22; - dx = x - n*M_LN2; - - /* Calculate t/512. */ - t = dx + THREEp42; - t -= THREEp42; - dx -= t; - - /* Compute tval = t. */ - tval = (int) (t * 512.0); - - if (t >= 0) - delta = - __exp_deltatable[tval]; - else - delta = __exp_deltatable[-tval]; - - /* Compute ex2 = 2^n e^(t/512+delta[t]). */ - ex2_u.d = __exp_atable[tval+177]; - ex2_u.ieee.exponent += (int) n; - - /* Approximate e^(dx+delta) - 1, using a second-degree polynomial, - with maximum error in [-2^-10-2^-28,2^-10+2^-28] - less than 5e-11. */ - x22 = (0.5000000496709180453 * dx + 1.0000001192102037084) * dx + delta; - - /* Return result. */ - fesetenv (&oldenv); - - result = x22 * ex2_u.d + ex2_u.d; - return (float) result; - } - /* Exceptional cases: */ - else if (isless (x, himark)) - { - if (__isinff (x)) - /* e^-inf == 0, with no error. */ - return 0; - else - /* Underflow */ - return TWOM100 * TWOM100; - } - else - /* Return x, if x is a NaN or Inf; or overflow, otherwise. */ - return TWO127*x; -} |