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Diffstat (limited to 'libm/src/s_exp2f.c')
| -rw-r--r-- | libm/src/s_exp2f.c | 141 |
1 files changed, 0 insertions, 141 deletions
diff --git a/libm/src/s_exp2f.c b/libm/src/s_exp2f.c deleted file mode 100644 index 5e98e8a..0000000 --- a/libm/src/s_exp2f.c +++ /dev/null @@ -1,141 +0,0 @@ -/*- - * Copyright (c) 2005 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 <sys/cdefs.h> -/* __FBSDID("$FreeBSD: src/lib/msun/src/s_exp2f.c,v 1.1 2005/04/05 02:57:15 das Exp $"); */ - -#include "math.h" -#include "math_private.h" - -#define TBLBITS 4 -#define TBLSIZE (1 << TBLBITS) - -static const float - huge = 0x1p100f, - twom100 = 0x1p-100f, - redux = 0x1.8p23f / TBLSIZE, - P1 = 0x1.62e430p-1f, - P2 = 0x1.ebfbe0p-3f, - P3 = 0x1.c6b348p-5f, - P4 = 0x1.3b2c9cp-7f; - -static const double exp2ft[TBLSIZE] = { - 0x1.6a09e667f3bcdp-1, - 0x1.7a11473eb0187p-1, - 0x1.8ace5422aa0dbp-1, - 0x1.9c49182a3f090p-1, - 0x1.ae89f995ad3adp-1, - 0x1.c199bdd85529cp-1, - 0x1.d5818dcfba487p-1, - 0x1.ea4afa2a490dap-1, - 0x1.0000000000000p+0, - 0x1.0b5586cf9890fp+0, - 0x1.172b83c7d517bp+0, - 0x1.2387a6e756238p+0, - 0x1.306fe0a31b715p+0, - 0x1.3dea64c123422p+0, - 0x1.4bfdad5362a27p+0, - 0x1.5ab07dd485429p+0, -}; - -/* - * exp2f(x): compute the base 2 exponential of x - * - * Accuracy: Peak error < 0.501 ulp; location of peak: -0.030110927. - * - * Method: (equally-spaced tables) - * - * Reduce x: - * x = 2**k + y, for integer k and |y| <= 1/2. - * Thus we have exp2f(x) = 2**k * exp2(y). - * - * Reduce y: - * y = i/TBLSIZE + z for integer i near y * TBLSIZE. - * Thus we have exp2(y) = exp2(i/TBLSIZE) * exp2(z), - * with |z| <= 2**-(TBLSIZE+1). - * - * We compute exp2(i/TBLSIZE) via table lookup and exp2(z) via a - * degree-4 minimax polynomial with maximum error under 1.4 * 2**-33. - * Using double precision in the final calculation avoids roundoff error. - * - * This method is due to Tang, but I do not use his suggested parameters: - * - * Tang, P. Table-driven Implementation of the Exponential Function - * in IEEE Floating-Point Arithmetic. TOMS 15(2), 144-157 (1989). - */ -float -exp2f(float x) -{ - double tv; - float r, z; - volatile float t; /* prevent gcc from using too much precision */ - uint32_t hx, hr, ix, i0; - int32_t k; - - /* Filter out exceptional cases. */ - GET_FLOAT_WORD(hx,x); - ix = hx & 0x7fffffff; /* high word of |x| */ - if(ix >= 0x43000000) { /* |x| >= 128 */ - if(ix >= 0x7f800000) { - if ((ix & 0x7fffff) != 0 || (hx & 0x80000000) == 0) - return (x); /* x is NaN or +Inf */ - else - return (0.0); /* x is -Inf */ - } - if(x >= 0x1.0p7f) - return (huge * huge); /* overflow */ - if(x <= -0x1.2cp7f) - return (twom100 * twom100); /* underflow */ - } else if (ix <= 0x33000000) { /* |x| <= 0x1p-25 */ - return (1.0f + x); - } - - /* Reduce x, computing z, i0, and k. */ - t = x + redux; - GET_FLOAT_WORD(i0, t); - i0 += TBLSIZE / 2; - k = (i0 >> TBLBITS) << 23; - i0 &= TBLSIZE - 1; - t -= redux; - z = x - t; - - /* Compute r = exp2(y) = exp2ft[i0] * p(z). */ - tv = exp2ft[i0]; - r = tv + tv * (z * (P1 + z * (P2 + z * (P3 + z * P4)))); - - /* Scale by 2**(k>>23). */ - if(k >= -125 << 23) { - if (k != 0) { - GET_FLOAT_WORD(hr, r); - SET_FLOAT_WORD(r, hr + k); - } - return (r); - } else { - GET_FLOAT_WORD(hr, r); - SET_FLOAT_WORD(r, hr + (k + (100 << 23))); - return (r * twom100); - } -} |