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88 lines
2.3 KiB
C
88 lines
2.3 KiB
C
/* Compute cosine of argument.
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Copyright (C) 2018-2020 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <stdint.h>
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#include <math.h>
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#include <math-barriers.h>
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#include <libm-alias-float.h>
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#include "math_config.h"
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#include "s_sincosf.h"
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#ifndef COSF
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# define COSF_FUNC __cosf
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#else
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# define COSF_FUNC COSF
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#endif
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/* Fast cosf implementation. Worst-case ULP is 0.5607, maximum relative
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error is 0.5303 * 2^-23. A single-step range reduction is used for
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small values. Large inputs have their range reduced using fast integer
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arithmetic.
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*/
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float
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COSF_FUNC (float y)
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{
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double x = y;
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double s;
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int n;
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const sincos_t *p = &__sincosf_table[0];
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if (abstop12 (y) < abstop12 (pio4))
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{
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double x2 = x * x;
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if (__glibc_unlikely (abstop12 (y) < abstop12 (0x1p-12f)))
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return 1.0f;
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return sinf_poly (x, x2, p, 1);
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}
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else if (__glibc_likely (abstop12 (y) < abstop12 (120.0f)))
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{
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x = reduce_fast (x, p, &n);
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/* Setup the signs for sin and cos. */
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s = p->sign[n & 3];
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if (n & 2)
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p = &__sincosf_table[1];
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return sinf_poly (x * s, x * x, p, n ^ 1);
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}
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else if (abstop12 (y) < abstop12 (INFINITY))
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{
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uint32_t xi = asuint (y);
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int sign = xi >> 31;
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x = reduce_large (xi, &n);
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/* Setup signs for sin and cos - include original sign. */
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s = p->sign[(n + sign) & 3];
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if ((n + sign) & 2)
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p = &__sincosf_table[1];
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return sinf_poly (x * s, x * x, p, n ^ 1);
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}
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else
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return __math_invalidf (y);
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}
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#ifndef COSF
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libm_alias_float (__cos, cos)
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#endif
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