/* ---------------------------------------------------------------------- | |
* Copyright (C) 2010-2014 ARM Limited. All rights reserved. | |
* | |
* $Date: 12. March 2014 | |
* $Revision: V1.4.4 | |
* | |
* Project: CMSIS DSP Library | |
* Title: arm_cos_f32.c | |
* | |
* Description: Fast cosine calculation for floating-point values. | |
* | |
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0 | |
* | |
* Redistribution and use in source and binary forms, with or without | |
* modification, are permitted provided that the following conditions | |
* are met: | |
* - Redistributions of source code must retain the above copyright | |
* notice, this list of conditions and the following disclaimer. | |
* - 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. | |
* - Neither the name of ARM LIMITED nor the names of its contributors | |
* may be used to endorse or promote products derived from this | |
* software without specific prior written permission. | |
* | |
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 | |
* COPYRIGHT OWNER 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 "arm_math.h" | |
#include "arm_common_tables.h" | |
/** | |
* @ingroup groupFastMath | |
*/ | |
/** | |
* @defgroup cos Cosine | |
* | |
* Computes the trigonometric cosine function using a combination of table lookup | |
* and cubic 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 cubic interpolation. | |
* The steps used are: | |
* -# Calculation of the nearest integer table index | |
* -# Fetch the four table values a, b, c, and d | |
* -# Compute the fractional portion (fract) of the table index. | |
* -# Calculation of wa, wb, wc, wd | |
* -# The final result equals <code>a*wa + b*wb + c*wc + d*wd</code> | |
* | |
* where | |
* <pre> | |
* a=Table[index-1]; | |
* b=Table[index+0]; | |
* c=Table[index+1]; | |
* d=Table[index+2]; | |
* </pre> | |
* and | |
* <pre> | |
* wa=-(1/6)*fract.^3 + (1/2)*fract.^2 - (1/3)*fract; | |
* wb=(1/2)*fract.^3 - fract.^2 - (1/2)*fract + 1; | |
* wc=-(1/2)*fract.^3+(1/2)*fract.^2+fract; | |
* wd=(1/6)*fract.^3 - (1/6)*fract; | |
* </pre> | |
*/ | |
/** | |
* @addtogroup cos | |
* @{ | |
*/ | |
/** | |
* @brief Fast approximation to the trigonometric cosine function for floating-point data. | |
* @param[in] x input value in radians. | |
* @return cos(x). | |
*/ | |
float32_t arm_cos_f32( | |
float32_t x) | |
{ | |
float32_t cosVal, fract, in; /* Temporary variables for input, output */ | |
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 the input to [0 1] range from [0 2*PI] , divide input by 2*pi, add 0.25 (pi/2) to read sine table */ | |
in = x * 0.159154943092f + 0.25f; | |
/* 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) & 0x1ff; | |
/* fractional value calculation */ | |
fract = findex - (float32_t) index; | |
/* Read two nearest values of input value from the cos table */ | |
a = sinTable_f32[index]; | |
b = sinTable_f32[index+1]; | |
/* Linear interpolation process */ | |
cosVal = (1.0f-fract)*a + fract*b; | |
/* Return the output value */ | |
return (cosVal); | |
} | |
/** | |
* @} end of cos group | |
*/ |