105 lines
2.7 KiB
C
105 lines
2.7 KiB
C
/************************************************************************
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* libc/math/lib_sinf.c
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*
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* This file is a part of NuttX:
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*
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* Copyright (C) 2012 Gregory Nutt. All rights reserved.
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* Ported by: Darcy Gong
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*
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* It derives from the Rhombs OS math library by Nick Johnson which has
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* a compatibile, MIT-style license:
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*
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* Copyright (C) 2009-2011 Nick Johnson <nickbjohnson4224 at gmail.com>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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************************************************************************/
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/************************************************************************
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* Included Files
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************************************************************************/
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#include <sys/types.h>
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#include <math.h>
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/************************************************************************
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* Private Data
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************************************************************************/
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static float _flt_inv_fact[] =
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{
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1.0 / 1.0, // 1 / 1!
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1.0 / 6.0, // 1 / 3!
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1.0 / 120.0, // 1 / 5!
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1.0 / 5040.0, // 1 / 7!
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1.0 / 362880.0, // 1 / 9!
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1.0 / 39916800.0, // 1 / 11!
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};
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/************************************************************************
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* Public Functions
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************************************************************************/
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float sinf(float x)
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{
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float x_squared;
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float sin_x;
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size_t i;
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/* Move x to [-pi, pi) */
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x = fmodf(x, 2 * M_PI);
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if (x >= M_PI)
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{
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x -= 2 * M_PI;
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}
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if (x < -M_PI)
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{
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x += 2 * M_PI;
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}
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/* Move x to [-pi/2, pi/2) */
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if (x >= M_PI_2)
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{
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x = M_PI - x;
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}
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if (x < -M_PI_2)
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{
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x = -M_PI - x;
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}
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x_squared = x * x;
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sin_x = 0.0;
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/* Perform Taylor series approximation for sin(x) with six terms */
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for (i = 0; i < 6; i++)
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{
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if (i % 2 == 0)
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{
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sin_x += x * _flt_inv_fact[i];
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}
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else
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{
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sin_x -= x * _flt_inv_fact[i];
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}
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x *= x_squared;
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}
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return sin_x;
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}
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