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/* ----------------------------------------------------------------------
* Project: CMSIS DSP Library
* Title: arm_sin_f32.c
* Description: Fast sine calculation for floating-point values
*
* $Date: 18. March 2019
* $Revision: V1.6.0
*
* Target Processor: Cortex-M cores
* -------------------------------------------------------------------- */
/*
* Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved.
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the License); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an AS IS BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "arm_math.h"
#include "arm_common_tables.h"
/**
@ingroup groupFastMath
*/
/**
@defgroup sin Sine
Computes the trigonometric sine function using a combination of table lookup
and linear interpolation. There are separate functions for
Q15, Q31, and floating-point data types.
The input to the floating-point version is in radians while the
fixed-point Q15 and Q31 have a scaled input with the range
[0 +0.9999] mapping to [0 2*pi). The fixed-point range is chosen so that a
value of 2*pi wraps around to 0.
The implementation is based on table lookup using 256 values together with linear interpolation.
The steps used are:
-# Calculation of the nearest integer table index
-# Compute the fractional portion (fract) of the table index.
-# The final result equals <code>(1.0f-fract)*a + fract*b;</code>
where
<pre>
b = Table[index];
c = Table[index+1];
</pre>
*/
/**
@addtogroup sin
@{
*/
/**
@brief Fast approximation to the trigonometric sine function for floating-point data.
@param[in] x input value in radians.
@return sin(x)
*/
float32_t arm_sin_f32(
float32_t x)
{
float32_t sinVal, fract, in; /* Temporary input, output variables */
uint16_t index; /* Index variable */
float32_t a, b; /* Two nearest output values */
int32_t n;
float32_t findex;
/* input x is in radians */
/* Scale input to [0 1] range from [0 2*PI] , divide input by 2*pi */
in = x * 0.159154943092f;
/* Calculation of floor value of input */
n = (int32_t) in;
/* Make negative values towards -infinity */
if (in < 0.0f)
{
n--;
}
/* Map input value to [0 1] */
in = in - (float32_t) n;
/* Calculation of index of the table */
findex = (float32_t)FAST_MATH_TABLE_SIZE * in;
index = (uint16_t)findex;
/* when "in" is exactly 1, we need to rotate the index down to 0 */
if (index >= FAST_MATH_TABLE_SIZE) {
index = 0;
findex -= (float32_t)FAST_MATH_TABLE_SIZE;
}
/* fractional value calculation */
fract = findex - (float32_t) index;
/* Read two nearest values of input value from the sin table */
a = sinTable_f32[index];
b = sinTable_f32[index+1];
/* Linear interpolation process */
sinVal = (1.0f - fract) * a + fract * b;
/* Return output value */
return (sinVal);
}
/**
@} end of sin group
*/
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