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718 lines
26 KiB
C
718 lines
26 KiB
C
/*-
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* Copyright (c) 2007-2013 Bruce D. Evans
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice unmodified, this list of conditions, and the following
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* disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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/**
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* Implementation of the natural logarithm of x for Intel 80-bit format.
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*
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* First decompose x into its base 2 representation:
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*
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* log(x) = log(X * 2**k), where X is in [1, 2)
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* = log(X) + k * log(2).
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*
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* Let X = X_i + e, where X_i is the center of one of the intervals
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* [-1.0/256, 1.0/256), [1.0/256, 3.0/256), .... [2.0-1.0/256, 2.0+1.0/256)
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* and X is in this interval. Then
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*
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* log(X) = log(X_i + e)
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* = log(X_i * (1 + e / X_i))
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* = log(X_i) + log(1 + e / X_i).
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*
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* The values log(X_i) are tabulated below. Let d = e / X_i and use
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*
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* log(1 + d) = p(d)
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*
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* where p(d) = d - 0.5*d*d + ... is a special minimax polynomial of
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* suitably high degree.
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*
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* To get sufficiently small roundoff errors, k * log(2), log(X_i), and
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* sometimes (if |k| is not large) the first term in p(d) must be evaluated
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* and added up in extra precision. Extra precision is not needed for the
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* rest of p(d). In the worst case when k = 0 and log(X_i) is 0, the final
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* error is controlled mainly by the error in the second term in p(d). The
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* error in this term itself is at most 0.5 ulps from the d*d operation in
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* it. The error in this term relative to the first term is thus at most
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* 0.5 * |-0.5| * |d| < 1.0/1024 ulps. We aim for an accumulated error of
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* at most twice this at the point of the final rounding step. Thus the
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* final error should be at most 0.5 + 1.0/512 = 0.5020 ulps. Exhaustive
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* testing of a float variant of this function showed a maximum final error
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* of 0.5008 ulps. Non-exhaustive testing of a double variant of this
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* function showed a maximum final error of 0.5078 ulps (near 1+1.0/256).
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*
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* We made the maximum of |d| (and thus the total relative error and the
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* degree of p(d)) small by using a large number of intervals. Using
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* centers of intervals instead of endpoints reduces this maximum by a
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* factor of 2 for a given number of intervals. p(d) is special only
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* in beginning with the Taylor coefficients 0 + 1*d, which tends to happen
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* naturally. The most accurate minimax polynomial of a given degree might
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* be different, but then we wouldn't want it since we would have to do
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* extra work to avoid roundoff error (especially for P0*d instead of d).
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*/
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#ifdef DEBUG
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#include <assert.h>
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#include <fenv.h>
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#endif
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#ifdef __i386__
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#include <ieeefp.h>
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#endif
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#include "fpmath.h"
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#include "math.h"
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#define i386_SSE_GOOD
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#ifndef NO_STRUCT_RETURN
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#define STRUCT_RETURN
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#endif
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#include "math_private.h"
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#if !defined(NO_UTAB) && !defined(NO_UTABL)
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#define USE_UTAB
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#endif
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/*
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* Domain [-0.005280, 0.004838], range ~[-5.1736e-22, 5.1738e-22]:
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* |log(1 + d)/d - p(d)| < 2**-70.7
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*/
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static const double
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P2 = -0.5,
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P3 = 3.3333333333333359e-1, /* 0x1555555555555a.0p-54 */
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P4 = -2.5000000000004424e-1, /* -0x1000000000031d.0p-54 */
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P5 = 1.9999999992970016e-1, /* 0x1999999972f3c7.0p-55 */
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P6 = -1.6666666072191585e-1, /* -0x15555548912c09.0p-55 */
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P7 = 1.4286227413310518e-1, /* 0x12494f9d9def91.0p-55 */
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P8 = -1.2518388626763144e-1; /* -0x1006068cc0b97c.0p-55 */
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static volatile const double zero = 0;
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#define INTERVALS 128
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#define LOG2_INTERVALS 7
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#define TSIZE (INTERVALS + 1)
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#define G(i) (T[(i)].G)
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#define F_hi(i) (T[(i)].F_hi)
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#define F_lo(i) (T[(i)].F_lo)
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#define ln2_hi F_hi(TSIZE - 1)
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#define ln2_lo F_lo(TSIZE - 1)
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#define E(i) (U[(i)].E)
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#define H(i) (U[(i)].H)
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static const struct {
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float G; /* 1/(1 + i/128) rounded to 8/9 bits */
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float F_hi; /* log(1 / G_i) rounded (see below) */
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double F_lo; /* next 53 bits for log(1 / G_i) */
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} T[TSIZE] = {
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/*
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* ln2_hi and each F_hi(i) are rounded to a number of bits that
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* makes F_hi(i) + dk*ln2_hi exact for all i and all dk.
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*
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* The last entry (for X just below 2) is used to define ln2_hi
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* and ln2_lo, to ensure that F_hi(i) and F_lo(i) cancel exactly
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* with dk*ln2_hi and dk*ln2_lo, respectively, when dk = -1.
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* This is needed for accuracy when x is just below 1. (To avoid
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* special cases, such x are "reduced" strangely to X just below
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* 2 and dk = -1, and then the exact cancellation is needed
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* because any the error from any non-exactness would be too
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* large).
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*
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* We want to share this table between double precision and ld80,
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* so the relevant range of dk is the larger one of ld80
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* ([-16445, 16383]) and the relevant exactness requirement is
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* the stricter one of double precision. The maximum number of
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* bits in F_hi(i) that works is very dependent on i but has
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* a minimum of 33. We only need about 12 bits in F_hi(i) for
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* it to provide enough extra precision in double precision (11
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* more than that are required for ld80).
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*
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* We round F_hi(i) to 24 bits so that it can have type float,
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* mainly to minimize the size of the table. Using all 24 bits
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* in a float for it automatically satisfies the above constraints.
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*/
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0x800000.0p-23, 0, 0,
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0xfe0000.0p-24, 0x8080ac.0p-30, -0x14ee431dae6675.0p-84,
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0xfc0000.0p-24, 0x8102b3.0p-29, -0x1db29ee2d83718.0p-84,
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0xfa0000.0p-24, 0xc24929.0p-29, 0x1191957d173698.0p-83,
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0xf80000.0p-24, 0x820aec.0p-28, 0x13ce8888e02e79.0p-82,
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0xf60000.0p-24, 0xa33577.0p-28, -0x17a4382ce6eb7c.0p-82,
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0xf48000.0p-24, 0xbc42cb.0p-28, -0x172a21161a1076.0p-83,
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0xf30000.0p-24, 0xd57797.0p-28, -0x1e09de07cb9589.0p-82,
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0xf10000.0p-24, 0xf7518e.0p-28, 0x1ae1eec1b036c5.0p-91,
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0xef0000.0p-24, 0x8cb9df.0p-27, -0x1d7355325d560e.0p-81,
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0xed8000.0p-24, 0x999ec0.0p-27, -0x1f9f02d256d503.0p-82,
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0xec0000.0p-24, 0xa6988b.0p-27, -0x16fc0a9d12c17a.0p-83,
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0xea0000.0p-24, 0xb80698.0p-27, 0x15d581c1e8da9a.0p-81,
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0xe80000.0p-24, 0xc99af3.0p-27, -0x1535b3ba8f150b.0p-83,
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0xe70000.0p-24, 0xd273b2.0p-27, 0x163786f5251af0.0p-85,
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0xe50000.0p-24, 0xe442c0.0p-27, 0x1bc4b2368e32d5.0p-84,
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0xe38000.0p-24, 0xf1b83f.0p-27, 0x1c6090f684e676.0p-81,
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0xe20000.0p-24, 0xff448a.0p-27, -0x1890aa69ac9f42.0p-82,
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0xe08000.0p-24, 0x8673f6.0p-26, 0x1b9985194b6b00.0p-80,
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0xdf0000.0p-24, 0x8d515c.0p-26, -0x1dc08d61c6ef1e.0p-83,
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0xdd8000.0p-24, 0x943a9e.0p-26, -0x1f72a2dac729b4.0p-82,
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0xdc0000.0p-24, 0x9b2fe6.0p-26, -0x1fd4dfd3a0afb9.0p-80,
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0xda8000.0p-24, 0xa2315d.0p-26, -0x11b26121629c47.0p-82,
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0xd90000.0p-24, 0xa93f2f.0p-26, 0x1286d633e8e569.0p-81,
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0xd78000.0p-24, 0xb05988.0p-26, 0x16128eba936770.0p-84,
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0xd60000.0p-24, 0xb78094.0p-26, 0x16ead577390d32.0p-80,
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0xd50000.0p-24, 0xbc4c6c.0p-26, 0x151131ccf7c7b7.0p-81,
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0xd38000.0p-24, 0xc3890a.0p-26, -0x115e2cd714bd06.0p-80,
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0xd20000.0p-24, 0xcad2d7.0p-26, -0x1847f406ebd3b0.0p-82,
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0xd10000.0p-24, 0xcfb620.0p-26, 0x1c2259904d6866.0p-81,
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0xcf8000.0p-24, 0xd71653.0p-26, 0x1ece57a8d5ae55.0p-80,
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0xce0000.0p-24, 0xde843a.0p-26, -0x1f109d4bc45954.0p-81,
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0xcd0000.0p-24, 0xe37fde.0p-26, 0x1bc03dc271a74d.0p-81,
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0xcb8000.0p-24, 0xeb050c.0p-26, -0x1bf2badc0df842.0p-85,
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0xca0000.0p-24, 0xf29878.0p-26, -0x18efededd89fbe.0p-87,
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0xc90000.0p-24, 0xf7ad6f.0p-26, 0x1373ff977baa69.0p-81,
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0xc80000.0p-24, 0xfcc8e3.0p-26, 0x196766f2fb3283.0p-80,
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0xc68000.0p-24, 0x823f30.0p-25, 0x19bd076f7c434e.0p-79,
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0xc58000.0p-24, 0x84d52c.0p-25, -0x1a327257af0f46.0p-79,
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0xc40000.0p-24, 0x88bc74.0p-25, 0x113f23def19c5a.0p-81,
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0xc30000.0p-24, 0x8b5ae6.0p-25, 0x1759f6e6b37de9.0p-79,
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0xc20000.0p-24, 0x8dfccb.0p-25, 0x1ad35ca6ed5148.0p-81,
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0xc10000.0p-24, 0x90a22b.0p-25, 0x1a1d71a87deba4.0p-79,
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0xbf8000.0p-24, 0x94a0d8.0p-25, -0x139e5210c2b731.0p-80,
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0xbe8000.0p-24, 0x974f16.0p-25, -0x18f6ebcff3ed73.0p-81,
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0xbd8000.0p-24, 0x9a00f1.0p-25, -0x1aa268be39aab7.0p-79,
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0xbc8000.0p-24, 0x9cb672.0p-25, -0x14c8815839c566.0p-79,
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0xbb0000.0p-24, 0xa0cda1.0p-25, 0x1eaf46390dbb24.0p-81,
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0xba0000.0p-24, 0xa38c6e.0p-25, 0x138e20d831f698.0p-81,
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0xb90000.0p-24, 0xa64f05.0p-25, -0x1e8d3c41123616.0p-82,
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0xb80000.0p-24, 0xa91570.0p-25, 0x1ce28f5f3840b2.0p-80,
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0xb70000.0p-24, 0xabdfbb.0p-25, -0x186e5c0a424234.0p-79,
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0xb60000.0p-24, 0xaeadef.0p-25, -0x14d41a0b2a08a4.0p-83,
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0xb50000.0p-24, 0xb18018.0p-25, 0x16755892770634.0p-79,
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0xb40000.0p-24, 0xb45642.0p-25, -0x16395ebe59b152.0p-82,
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0xb30000.0p-24, 0xb73077.0p-25, 0x1abc65c8595f09.0p-80,
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0xb20000.0p-24, 0xba0ec4.0p-25, -0x1273089d3dad89.0p-79,
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0xb10000.0p-24, 0xbcf133.0p-25, 0x10f9f67b1f4bbf.0p-79,
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0xb00000.0p-24, 0xbfd7d2.0p-25, -0x109fab90486409.0p-80,
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0xaf0000.0p-24, 0xc2c2ac.0p-25, -0x1124680aa43333.0p-79,
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0xae8000.0p-24, 0xc439b3.0p-25, -0x1f360cc4710fc0.0p-80,
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0xad8000.0p-24, 0xc72afd.0p-25, -0x132d91f21d89c9.0p-80,
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0xac8000.0p-24, 0xca20a2.0p-25, -0x16bf9b4d1f8da8.0p-79,
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0xab8000.0p-24, 0xcd1aae.0p-25, 0x19deb5ce6a6a87.0p-81,
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0xaa8000.0p-24, 0xd0192f.0p-25, 0x1a29fb48f7d3cb.0p-79,
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0xaa0000.0p-24, 0xd19a20.0p-25, 0x1127d3c6457f9d.0p-81,
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0xa90000.0p-24, 0xd49f6a.0p-25, -0x1ba930e486a0ac.0p-81,
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0xa80000.0p-24, 0xd7a94b.0p-25, -0x1b6e645f31549e.0p-79,
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0xa70000.0p-24, 0xdab7d0.0p-25, 0x1118a425494b61.0p-80,
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0xa68000.0p-24, 0xdc40d5.0p-25, 0x1966f24d29d3a3.0p-80,
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0xa58000.0p-24, 0xdf566d.0p-25, -0x1d8e52eb2248f1.0p-82,
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0xa48000.0p-24, 0xe270ce.0p-25, -0x1ee370f96e6b68.0p-80,
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0xa40000.0p-24, 0xe3ffce.0p-25, 0x1d155324911f57.0p-80,
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0xa30000.0p-24, 0xe72179.0p-25, -0x1fe6e2f2f867d9.0p-80,
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0xa20000.0p-24, 0xea4812.0p-25, 0x1b7be9add7f4d4.0p-80,
|
|
0xa18000.0p-24, 0xebdd3d.0p-25, 0x1b3cfb3f7511dd.0p-79,
|
|
0xa08000.0p-24, 0xef0b5b.0p-25, -0x1220de1f730190.0p-79,
|
|
0xa00000.0p-24, 0xf0a451.0p-25, -0x176364c9ac81cd.0p-80,
|
|
0x9f0000.0p-24, 0xf3da16.0p-25, 0x1eed6b9aafac8d.0p-81,
|
|
0x9e8000.0p-24, 0xf576e9.0p-25, 0x1d593218675af2.0p-79,
|
|
0x9d8000.0p-24, 0xf8b47c.0p-25, -0x13e8eb7da053e0.0p-84,
|
|
0x9d0000.0p-24, 0xfa553f.0p-25, 0x1c063259bcade0.0p-79,
|
|
0x9c0000.0p-24, 0xfd9ac5.0p-25, 0x1ef491085fa3c1.0p-79,
|
|
0x9b8000.0p-24, 0xff3f8c.0p-25, 0x1d607a7c2b8c53.0p-79,
|
|
0x9a8000.0p-24, 0x814697.0p-24, -0x12ad3817004f3f.0p-78,
|
|
0x9a0000.0p-24, 0x821b06.0p-24, -0x189fc53117f9e5.0p-81,
|
|
0x990000.0p-24, 0x83c5f8.0p-24, 0x14cf15a048907b.0p-79,
|
|
0x988000.0p-24, 0x849c7d.0p-24, 0x1cbb1d35fb8287.0p-78,
|
|
0x978000.0p-24, 0x864ba6.0p-24, 0x1128639b814f9c.0p-78,
|
|
0x970000.0p-24, 0x87244c.0p-24, 0x184733853300f0.0p-79,
|
|
0x968000.0p-24, 0x87fdaa.0p-24, 0x109d23aef77dd6.0p-80,
|
|
0x958000.0p-24, 0x89b293.0p-24, -0x1a81ef367a59de.0p-78,
|
|
0x950000.0p-24, 0x8a8e20.0p-24, -0x121ad3dbb2f452.0p-78,
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|
0x948000.0p-24, 0x8b6a6a.0p-24, -0x1cfb981628af72.0p-79,
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|
0x938000.0p-24, 0x8d253a.0p-24, -0x1d21730ea76cfe.0p-79,
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|
0x930000.0p-24, 0x8e03c2.0p-24, 0x135cc00e566f77.0p-78,
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0x928000.0p-24, 0x8ee30d.0p-24, -0x10fcb5df257a26.0p-80,
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0x918000.0p-24, 0x90a3ee.0p-24, -0x16e171b15433d7.0p-79,
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0x910000.0p-24, 0x918587.0p-24, -0x1d050da07f3237.0p-79,
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0x908000.0p-24, 0x9267e7.0p-24, 0x1be03669a5268d.0p-79,
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0x8f8000.0p-24, 0x942f04.0p-24, 0x10b28e0e26c337.0p-79,
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|
0x8f0000.0p-24, 0x9513c3.0p-24, 0x1a1d820da57cf3.0p-78,
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|
0x8e8000.0p-24, 0x95f950.0p-24, -0x19ef8f13ae3cf1.0p-79,
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|
0x8e0000.0p-24, 0x96dfab.0p-24, -0x109e417a6e507c.0p-78,
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|
0x8d0000.0p-24, 0x98aed2.0p-24, 0x10d01a2c5b0e98.0p-79,
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|
0x8c8000.0p-24, 0x9997a2.0p-24, -0x1d6a50d4b61ea7.0p-78,
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|
0x8c0000.0p-24, 0x9a8145.0p-24, 0x1b3b190b83f952.0p-78,
|
|
0x8b8000.0p-24, 0x9b6bbf.0p-24, 0x13a69fad7e7abe.0p-78,
|
|
0x8b0000.0p-24, 0x9c5711.0p-24, -0x11cd12316f576b.0p-78,
|
|
0x8a8000.0p-24, 0x9d433b.0p-24, 0x1c95c444b807a2.0p-79,
|
|
0x898000.0p-24, 0x9f1e22.0p-24, -0x1b9c224ea698c3.0p-79,
|
|
0x890000.0p-24, 0xa00ce1.0p-24, 0x125ca93186cf0f.0p-81,
|
|
0x888000.0p-24, 0xa0fc80.0p-24, -0x1ee38a7bc228b3.0p-79,
|
|
0x880000.0p-24, 0xa1ed00.0p-24, -0x1a0db876613d20.0p-78,
|
|
0x878000.0p-24, 0xa2de62.0p-24, 0x193224e8516c01.0p-79,
|
|
0x870000.0p-24, 0xa3d0a9.0p-24, 0x1fa28b4d2541ad.0p-79,
|
|
0x868000.0p-24, 0xa4c3d6.0p-24, 0x1c1b5760fb4572.0p-78,
|
|
0x858000.0p-24, 0xa6acea.0p-24, 0x1fed5d0f65949c.0p-80,
|
|
0x850000.0p-24, 0xa7a2d4.0p-24, 0x1ad270c9d74936.0p-80,
|
|
0x848000.0p-24, 0xa899ab.0p-24, 0x199ff15ce53266.0p-79,
|
|
0x840000.0p-24, 0xa99171.0p-24, 0x1a19e15ccc45d2.0p-79,
|
|
0x838000.0p-24, 0xaa8a28.0p-24, -0x121a14ec532b36.0p-80,
|
|
0x830000.0p-24, 0xab83d1.0p-24, 0x1aee319980bff3.0p-79,
|
|
0x828000.0p-24, 0xac7e6f.0p-24, -0x18ffd9e3900346.0p-80,
|
|
0x820000.0p-24, 0xad7a03.0p-24, -0x1e4db102ce29f8.0p-80,
|
|
0x818000.0p-24, 0xae768f.0p-24, 0x17c35c55a04a83.0p-81,
|
|
0x810000.0p-24, 0xaf7415.0p-24, 0x1448324047019b.0p-78,
|
|
0x808000.0p-24, 0xb07298.0p-24, -0x1750ee3915a198.0p-78,
|
|
0x800000.0p-24, 0xb17218.0p-24, -0x105c610ca86c39.0p-81,
|
|
};
|
|
|
|
#ifdef USE_UTAB
|
|
static const struct {
|
|
float H; /* 1 + i/INTERVALS (exact) */
|
|
float E; /* H(i) * G(i) - 1 (exact) */
|
|
} U[TSIZE] = {
|
|
0x800000.0p-23, 0,
|
|
0x810000.0p-23, -0x800000.0p-37,
|
|
0x820000.0p-23, -0x800000.0p-35,
|
|
0x830000.0p-23, -0x900000.0p-34,
|
|
0x840000.0p-23, -0x800000.0p-33,
|
|
0x850000.0p-23, -0xc80000.0p-33,
|
|
0x860000.0p-23, -0xa00000.0p-36,
|
|
0x870000.0p-23, 0x940000.0p-33,
|
|
0x880000.0p-23, 0x800000.0p-35,
|
|
0x890000.0p-23, -0xc80000.0p-34,
|
|
0x8a0000.0p-23, 0xe00000.0p-36,
|
|
0x8b0000.0p-23, 0x900000.0p-33,
|
|
0x8c0000.0p-23, -0x800000.0p-35,
|
|
0x8d0000.0p-23, -0xe00000.0p-33,
|
|
0x8e0000.0p-23, 0x880000.0p-33,
|
|
0x8f0000.0p-23, -0xa80000.0p-34,
|
|
0x900000.0p-23, -0x800000.0p-35,
|
|
0x910000.0p-23, 0x800000.0p-37,
|
|
0x920000.0p-23, 0x900000.0p-35,
|
|
0x930000.0p-23, 0xd00000.0p-35,
|
|
0x940000.0p-23, 0xe00000.0p-35,
|
|
0x950000.0p-23, 0xc00000.0p-35,
|
|
0x960000.0p-23, 0xe00000.0p-36,
|
|
0x970000.0p-23, -0x800000.0p-38,
|
|
0x980000.0p-23, -0xc00000.0p-35,
|
|
0x990000.0p-23, -0xd00000.0p-34,
|
|
0x9a0000.0p-23, 0x880000.0p-33,
|
|
0x9b0000.0p-23, 0xe80000.0p-35,
|
|
0x9c0000.0p-23, -0x800000.0p-35,
|
|
0x9d0000.0p-23, 0xb40000.0p-33,
|
|
0x9e0000.0p-23, 0x880000.0p-34,
|
|
0x9f0000.0p-23, -0xe00000.0p-35,
|
|
0xa00000.0p-23, 0x800000.0p-33,
|
|
0xa10000.0p-23, -0x900000.0p-36,
|
|
0xa20000.0p-23, -0xb00000.0p-33,
|
|
0xa30000.0p-23, -0xa00000.0p-36,
|
|
0xa40000.0p-23, 0x800000.0p-33,
|
|
0xa50000.0p-23, -0xf80000.0p-35,
|
|
0xa60000.0p-23, 0x880000.0p-34,
|
|
0xa70000.0p-23, -0x900000.0p-33,
|
|
0xa80000.0p-23, -0x800000.0p-35,
|
|
0xa90000.0p-23, 0x900000.0p-34,
|
|
0xaa0000.0p-23, 0xa80000.0p-33,
|
|
0xab0000.0p-23, -0xac0000.0p-34,
|
|
0xac0000.0p-23, -0x800000.0p-37,
|
|
0xad0000.0p-23, 0xf80000.0p-35,
|
|
0xae0000.0p-23, 0xf80000.0p-34,
|
|
0xaf0000.0p-23, -0xac0000.0p-33,
|
|
0xb00000.0p-23, -0x800000.0p-33,
|
|
0xb10000.0p-23, -0xb80000.0p-34,
|
|
0xb20000.0p-23, -0x800000.0p-34,
|
|
0xb30000.0p-23, -0xb00000.0p-35,
|
|
0xb40000.0p-23, -0x800000.0p-35,
|
|
0xb50000.0p-23, -0xe00000.0p-36,
|
|
0xb60000.0p-23, -0x800000.0p-35,
|
|
0xb70000.0p-23, -0xb00000.0p-35,
|
|
0xb80000.0p-23, -0x800000.0p-34,
|
|
0xb90000.0p-23, -0xb80000.0p-34,
|
|
0xba0000.0p-23, -0x800000.0p-33,
|
|
0xbb0000.0p-23, -0xac0000.0p-33,
|
|
0xbc0000.0p-23, 0x980000.0p-33,
|
|
0xbd0000.0p-23, 0xbc0000.0p-34,
|
|
0xbe0000.0p-23, 0xe00000.0p-36,
|
|
0xbf0000.0p-23, -0xb80000.0p-35,
|
|
0xc00000.0p-23, -0x800000.0p-33,
|
|
0xc10000.0p-23, 0xa80000.0p-33,
|
|
0xc20000.0p-23, 0x900000.0p-34,
|
|
0xc30000.0p-23, -0x800000.0p-35,
|
|
0xc40000.0p-23, -0x900000.0p-33,
|
|
0xc50000.0p-23, 0x820000.0p-33,
|
|
0xc60000.0p-23, 0x800000.0p-38,
|
|
0xc70000.0p-23, -0x820000.0p-33,
|
|
0xc80000.0p-23, 0x800000.0p-33,
|
|
0xc90000.0p-23, -0xa00000.0p-36,
|
|
0xca0000.0p-23, -0xb00000.0p-33,
|
|
0xcb0000.0p-23, 0x840000.0p-34,
|
|
0xcc0000.0p-23, -0xd00000.0p-34,
|
|
0xcd0000.0p-23, 0x800000.0p-33,
|
|
0xce0000.0p-23, -0xe00000.0p-35,
|
|
0xcf0000.0p-23, 0xa60000.0p-33,
|
|
0xd00000.0p-23, -0x800000.0p-35,
|
|
0xd10000.0p-23, 0xb40000.0p-33,
|
|
0xd20000.0p-23, -0x800000.0p-35,
|
|
0xd30000.0p-23, 0xaa0000.0p-33,
|
|
0xd40000.0p-23, -0xe00000.0p-35,
|
|
0xd50000.0p-23, 0x880000.0p-33,
|
|
0xd60000.0p-23, -0xd00000.0p-34,
|
|
0xd70000.0p-23, 0x9c0000.0p-34,
|
|
0xd80000.0p-23, -0xb00000.0p-33,
|
|
0xd90000.0p-23, -0x800000.0p-38,
|
|
0xda0000.0p-23, 0xa40000.0p-33,
|
|
0xdb0000.0p-23, -0xdc0000.0p-34,
|
|
0xdc0000.0p-23, 0xc00000.0p-35,
|
|
0xdd0000.0p-23, 0xca0000.0p-33,
|
|
0xde0000.0p-23, -0xb80000.0p-34,
|
|
0xdf0000.0p-23, 0xd00000.0p-35,
|
|
0xe00000.0p-23, 0xc00000.0p-33,
|
|
0xe10000.0p-23, -0xf40000.0p-34,
|
|
0xe20000.0p-23, 0x800000.0p-37,
|
|
0xe30000.0p-23, 0x860000.0p-33,
|
|
0xe40000.0p-23, -0xc80000.0p-33,
|
|
0xe50000.0p-23, -0xa80000.0p-34,
|
|
0xe60000.0p-23, 0xe00000.0p-36,
|
|
0xe70000.0p-23, 0x880000.0p-33,
|
|
0xe80000.0p-23, -0xe00000.0p-33,
|
|
0xe90000.0p-23, -0xfc0000.0p-34,
|
|
0xea0000.0p-23, -0x800000.0p-35,
|
|
0xeb0000.0p-23, 0xe80000.0p-35,
|
|
0xec0000.0p-23, 0x900000.0p-33,
|
|
0xed0000.0p-23, 0xe20000.0p-33,
|
|
0xee0000.0p-23, -0xac0000.0p-33,
|
|
0xef0000.0p-23, -0xc80000.0p-34,
|
|
0xf00000.0p-23, -0x800000.0p-35,
|
|
0xf10000.0p-23, 0x800000.0p-35,
|
|
0xf20000.0p-23, 0xb80000.0p-34,
|
|
0xf30000.0p-23, 0x940000.0p-33,
|
|
0xf40000.0p-23, 0xc80000.0p-33,
|
|
0xf50000.0p-23, -0xf20000.0p-33,
|
|
0xf60000.0p-23, -0xc80000.0p-33,
|
|
0xf70000.0p-23, -0xa20000.0p-33,
|
|
0xf80000.0p-23, -0x800000.0p-33,
|
|
0xf90000.0p-23, -0xc40000.0p-34,
|
|
0xfa0000.0p-23, -0x900000.0p-34,
|
|
0xfb0000.0p-23, -0xc80000.0p-35,
|
|
0xfc0000.0p-23, -0x800000.0p-35,
|
|
0xfd0000.0p-23, -0x900000.0p-36,
|
|
0xfe0000.0p-23, -0x800000.0p-37,
|
|
0xff0000.0p-23, -0x800000.0p-39,
|
|
0x800000.0p-22, 0,
|
|
};
|
|
#endif /* USE_UTAB */
|
|
|
|
#ifdef STRUCT_RETURN
|
|
#define RETURN1(rp, v) do { \
|
|
(rp)->hi = (v); \
|
|
(rp)->lo_set = 0; \
|
|
return; \
|
|
} while (0)
|
|
|
|
#define RETURN2(rp, h, l) do { \
|
|
(rp)->hi = (h); \
|
|
(rp)->lo = (l); \
|
|
(rp)->lo_set = 1; \
|
|
return; \
|
|
} while (0)
|
|
|
|
struct ld {
|
|
long double hi;
|
|
long double lo;
|
|
int lo_set;
|
|
};
|
|
#else
|
|
#define RETURN1(rp, v) RETURNF(v)
|
|
#define RETURN2(rp, h, l) RETURNI((h) + (l))
|
|
#endif
|
|
|
|
#ifdef STRUCT_RETURN
|
|
static inline __always_inline void
|
|
k_logl(long double x, struct ld *rp)
|
|
#else
|
|
long double
|
|
logl(long double x)
|
|
#endif
|
|
{
|
|
long double d, dk, val_hi, val_lo, z;
|
|
uint64_t ix, lx;
|
|
int i, k;
|
|
uint16_t hx;
|
|
|
|
EXTRACT_LDBL80_WORDS(hx, lx, x);
|
|
k = -16383;
|
|
#if 0 /* Hard to do efficiently. Don't do it until we support all modes. */
|
|
if (x == 1)
|
|
RETURN1(rp, 0); /* log(1) = +0 in all rounding modes */
|
|
#endif
|
|
if (hx == 0 || hx >= 0x8000) { /* zero, negative or subnormal? */
|
|
if (((hx & 0x7fff) | lx) == 0)
|
|
RETURN1(rp, -1 / zero); /* log(+-0) = -Inf */
|
|
if (hx != 0)
|
|
/* log(neg or [pseudo-]NaN) = qNaN: */
|
|
RETURN1(rp, (x - x) / zero);
|
|
x *= 0x1.0p65; /* subnormal; scale up x */
|
|
/* including pseudo-subnormals */
|
|
EXTRACT_LDBL80_WORDS(hx, lx, x);
|
|
k = -16383 - 65;
|
|
} else if (hx >= 0x7fff || (lx & 0x8000000000000000ULL) == 0)
|
|
RETURN1(rp, x + x); /* log(Inf or NaN) = Inf or qNaN */
|
|
/* log(pseudo-Inf) = qNaN */
|
|
/* log(pseudo-NaN) = qNaN */
|
|
/* log(unnormal) = qNaN */
|
|
#ifndef STRUCT_RETURN
|
|
ENTERI();
|
|
#endif
|
|
k += hx;
|
|
ix = lx & 0x7fffffffffffffffULL;
|
|
dk = k;
|
|
|
|
/* Scale x to be in [1, 2). */
|
|
SET_LDBL_EXPSIGN(x, 0x3fff);
|
|
|
|
/* 0 <= i <= INTERVALS: */
|
|
#define L2I (64 - LOG2_INTERVALS)
|
|
i = (ix + (1LL << (L2I - 2))) >> (L2I - 1);
|
|
|
|
/*
|
|
* -0.005280 < d < 0.004838. In particular, the infinite-
|
|
* precision |d| is <= 2**-7. Rounding of G(i) to 8 bits
|
|
* ensures that d is representable without extra precision for
|
|
* this bound on |d| (since when this calculation is expressed
|
|
* as x*G(i)-1, the multiplication needs as many extra bits as
|
|
* G(i) has and the subtraction cancels 8 bits). But for
|
|
* most i (107 cases out of 129), the infinite-precision |d|
|
|
* is <= 2**-8. G(i) is rounded to 9 bits for such i to give
|
|
* better accuracy (this works by improving the bound on |d|,
|
|
* which in turn allows rounding to 9 bits in more cases).
|
|
* This is only important when the original x is near 1 -- it
|
|
* lets us avoid using a special method to give the desired
|
|
* accuracy for such x.
|
|
*/
|
|
if (0)
|
|
d = x * G(i) - 1;
|
|
else {
|
|
#ifdef USE_UTAB
|
|
d = (x - H(i)) * G(i) + E(i);
|
|
#else
|
|
long double x_hi, x_lo;
|
|
float fx_hi;
|
|
|
|
/*
|
|
* Split x into x_hi + x_lo to calculate x*G(i)-1 exactly.
|
|
* G(i) has at most 9 bits, so the splitting point is not
|
|
* critical.
|
|
*/
|
|
SET_FLOAT_WORD(fx_hi, (lx >> 40) | 0x3f800000);
|
|
x_hi = fx_hi;
|
|
x_lo = x - x_hi;
|
|
d = x_hi * G(i) - 1 + x_lo * G(i);
|
|
#endif
|
|
}
|
|
|
|
/*
|
|
* Our algorithm depends on exact cancellation of F_lo(i) and
|
|
* F_hi(i) with dk*ln_2_lo and dk*ln2_hi when k is -1 and i is
|
|
* at the end of the table. This and other technical complications
|
|
* make it difficult to avoid the double scaling in (dk*ln2) *
|
|
* log(base) for base != e without losing more accuracy and/or
|
|
* efficiency than is gained.
|
|
*/
|
|
z = d * d;
|
|
val_lo = z * d * z * (z * (d * P8 + P7) + (d * P6 + P5)) +
|
|
(F_lo(i) + dk * ln2_lo + z * d * (d * P4 + P3)) + z * P2;
|
|
val_hi = d;
|
|
#ifdef DEBUG
|
|
if (fetestexcept(FE_UNDERFLOW))
|
|
breakpoint();
|
|
#endif
|
|
|
|
_3sumF(val_hi, val_lo, F_hi(i) + dk * ln2_hi);
|
|
RETURN2(rp, val_hi, val_lo);
|
|
}
|
|
|
|
long double
|
|
log1pl(long double x)
|
|
{
|
|
long double d, d_hi, d_lo, dk, f_lo, val_hi, val_lo, z;
|
|
long double f_hi, twopminusk;
|
|
uint64_t ix, lx;
|
|
int i, k;
|
|
int16_t ax, hx;
|
|
|
|
DOPRINT_START(&x);
|
|
EXTRACT_LDBL80_WORDS(hx, lx, x);
|
|
if (hx < 0x3fff) { /* x < 1, or x neg NaN */
|
|
ax = hx & 0x7fff;
|
|
if (ax >= 0x3fff) { /* x <= -1, or x neg NaN */
|
|
if (ax == 0x3fff && lx == 0x8000000000000000ULL)
|
|
RETURNP(-1 / zero); /* log1p(-1) = -Inf */
|
|
/* log1p(x < 1, or x [pseudo-]NaN) = qNaN: */
|
|
RETURNP((x - x) / (x - x));
|
|
}
|
|
if (ax <= 0x3fbe) { /* |x| < 2**-64 */
|
|
if ((int)x == 0)
|
|
RETURNP(x); /* x with inexact if x != 0 */
|
|
}
|
|
f_hi = 1;
|
|
f_lo = x;
|
|
} else if (hx >= 0x7fff) { /* x +Inf or non-neg NaN */
|
|
RETURNP(x + x); /* log1p(Inf or NaN) = Inf or qNaN */
|
|
/* log1p(pseudo-Inf) = qNaN */
|
|
/* log1p(pseudo-NaN) = qNaN */
|
|
/* log1p(unnormal) = qNaN */
|
|
} else if (hx < 0x407f) { /* 1 <= x < 2**128 */
|
|
f_hi = x;
|
|
f_lo = 1;
|
|
} else { /* 2**128 <= x < +Inf */
|
|
f_hi = x;
|
|
f_lo = 0; /* avoid underflow of the P5 term */
|
|
}
|
|
ENTERI();
|
|
x = f_hi + f_lo;
|
|
f_lo = (f_hi - x) + f_lo;
|
|
|
|
EXTRACT_LDBL80_WORDS(hx, lx, x);
|
|
k = -16383;
|
|
|
|
k += hx;
|
|
ix = lx & 0x7fffffffffffffffULL;
|
|
dk = k;
|
|
|
|
SET_LDBL_EXPSIGN(x, 0x3fff);
|
|
twopminusk = 1;
|
|
SET_LDBL_EXPSIGN(twopminusk, 0x7ffe - (hx & 0x7fff));
|
|
f_lo *= twopminusk;
|
|
|
|
i = (ix + (1LL << (L2I - 2))) >> (L2I - 1);
|
|
|
|
/*
|
|
* x*G(i)-1 (with a reduced x) can be represented exactly, as
|
|
* above, but now we need to evaluate the polynomial on d =
|
|
* (x+f_lo)*G(i)-1 and extra precision is needed for that.
|
|
* Since x+x_lo is a hi+lo decomposition and subtracting 1
|
|
* doesn't lose too many bits, an inexact calculation for
|
|
* f_lo*G(i) is good enough.
|
|
*/
|
|
if (0)
|
|
d_hi = x * G(i) - 1;
|
|
else {
|
|
#ifdef USE_UTAB
|
|
d_hi = (x - H(i)) * G(i) + E(i);
|
|
#else
|
|
long double x_hi, x_lo;
|
|
float fx_hi;
|
|
|
|
SET_FLOAT_WORD(fx_hi, (lx >> 40) | 0x3f800000);
|
|
x_hi = fx_hi;
|
|
x_lo = x - x_hi;
|
|
d_hi = x_hi * G(i) - 1 + x_lo * G(i);
|
|
#endif
|
|
}
|
|
d_lo = f_lo * G(i);
|
|
|
|
/*
|
|
* This is _2sumF(d_hi, d_lo) inlined. The condition
|
|
* (d_hi == 0 || |d_hi| >= |d_lo|) for using _2sumF() is not
|
|
* always satisifed, so it is not clear that this works, but
|
|
* it works in practice. It works even if it gives a wrong
|
|
* normalized d_lo, since |d_lo| > |d_hi| implies that i is
|
|
* nonzero and d is tiny, so the F(i) term dominates d_lo.
|
|
* In float precision:
|
|
* (By exhaustive testing, the worst case is d_hi = 0x1.bp-25.
|
|
* And if d is only a little tinier than that, we would have
|
|
* another underflow problem for the P3 term; this is also ruled
|
|
* out by exhaustive testing.)
|
|
*/
|
|
d = d_hi + d_lo;
|
|
d_lo = d_hi - d + d_lo;
|
|
d_hi = d;
|
|
|
|
z = d * d;
|
|
val_lo = z * d * z * (z * (d * P8 + P7) + (d * P6 + P5)) +
|
|
(F_lo(i) + dk * ln2_lo + d_lo + z * d * (d * P4 + P3)) + z * P2;
|
|
val_hi = d_hi;
|
|
#ifdef DEBUG
|
|
if (fetestexcept(FE_UNDERFLOW))
|
|
breakpoint();
|
|
#endif
|
|
|
|
_3sumF(val_hi, val_lo, F_hi(i) + dk * ln2_hi);
|
|
RETURN2PI(val_hi, val_lo);
|
|
}
|
|
|
|
#ifdef STRUCT_RETURN
|
|
|
|
long double
|
|
logl(long double x)
|
|
{
|
|
struct ld r;
|
|
|
|
ENTERI();
|
|
DOPRINT_START(&x);
|
|
k_logl(x, &r);
|
|
RETURNSPI(&r);
|
|
}
|
|
|
|
static const double
|
|
invln10_hi = 4.3429448190317999e-1, /* 0x1bcb7b1526e000.0p-54 */
|
|
invln10_lo = 7.1842412889749798e-14, /* 0x1438ca9aadd558.0p-96 */
|
|
invln2_hi = 1.4426950408887933e0, /* 0x171547652b8000.0p-52 */
|
|
invln2_lo = 1.7010652264631490e-13; /* 0x17f0bbbe87fed0.0p-95 */
|
|
|
|
long double
|
|
log10l(long double x)
|
|
{
|
|
struct ld r;
|
|
long double hi, lo;
|
|
|
|
ENTERI();
|
|
DOPRINT_START(&x);
|
|
k_logl(x, &r);
|
|
if (!r.lo_set)
|
|
RETURNPI(r.hi);
|
|
_2sumF(r.hi, r.lo);
|
|
hi = (float)r.hi;
|
|
lo = r.lo + (r.hi - hi);
|
|
RETURN2PI(invln10_hi * hi,
|
|
(invln10_lo + invln10_hi) * lo + invln10_lo * hi);
|
|
}
|
|
|
|
long double
|
|
log2l(long double x)
|
|
{
|
|
struct ld r;
|
|
long double hi, lo;
|
|
|
|
ENTERI();
|
|
DOPRINT_START(&x);
|
|
k_logl(x, &r);
|
|
if (!r.lo_set)
|
|
RETURNPI(r.hi);
|
|
_2sumF(r.hi, r.lo);
|
|
hi = (float)r.hi;
|
|
lo = r.lo + (r.hi - hi);
|
|
RETURN2PI(invln2_hi * hi,
|
|
(invln2_lo + invln2_hi) * lo + invln2_lo * hi);
|
|
}
|
|
|
|
#endif /* STRUCT_RETURN */
|