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| bfc108 | 1 | /* ---------------------------------------------------------------------- |
| Q | 2 | * Copyright (C) 2010-2014 ARM Limited. All rights reserved. |
| 3 | * | |
| 4 | * $Date: 21. September 2015 | |
| 5 | * $Revision: V.1.4.5 a | |
| 6 | * | |
| 7 | * Project: CMSIS DSP Library | |
| 8 | * Title: arm_cos_f32.c | |
| 9 | * | |
| 10 | * Description: Fast cosine calculation for floating-point values. | |
| 11 | * | |
| 12 | * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0 | |
| 13 | * | |
| 14 | * Redistribution and use in source and binary forms, with or without | |
| 15 | * modification, are permitted provided that the following conditions | |
| 16 | * are met: | |
| 17 | * - Redistributions of source code must retain the above copyright | |
| 18 | * notice, this list of conditions and the following disclaimer. | |
| 19 | * - Redistributions in binary form must reproduce the above copyright | |
| 20 | * notice, this list of conditions and the following disclaimer in | |
| 21 | * the documentation and/or other materials provided with the | |
| 22 | * distribution. | |
| 23 | * - Neither the name of ARM LIMITED nor the names of its contributors | |
| 24 | * may be used to endorse or promote products derived from this | |
| 25 | * software without specific prior written permission. | |
| 26 | * | |
| 27 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | |
| 28 | * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | |
| 29 | * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS | |
| 30 | * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE | |
| 31 | * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, | |
| 32 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, | |
| 33 | * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; | |
| 34 | * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER | |
| 35 | * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | |
| 36 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN | |
| 37 | * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE | |
| 38 | * POSSIBILITY OF SUCH DAMAGE. | |
| 39 | * -------------------------------------------------------------------- */ | |
| 40 | ||
| 41 | #include "arm_math.h" | |
| 42 | #include "arm_common_tables.h" | |
| 43 | /** | |
| 44 | * @ingroup groupFastMath | |
| 45 | */ | |
| 46 | ||
| 47 | /** | |
| 48 | * @defgroup cos Cosine | |
| 49 | * | |
| 50 | * Computes the trigonometric cosine function using a combination of table lookup | |
| 51 | * and linear interpolation. There are separate functions for | |
| 52 | * Q15, Q31, and floating-point data types. | |
| 53 | * The input to the floating-point version is in radians while the | |
| 54 | * fixed-point Q15 and Q31 have a scaled input with the range | |
| 55 | * [0 +0.9999] mapping to [0 2*pi). The fixed-point range is chosen so that a | |
| 56 | * value of 2*pi wraps around to 0. | |
| 57 | * | |
| 58 | * The implementation is based on table lookup using 256 values together with linear interpolation. | |
| 59 | * The steps used are: | |
| 60 | * -# Calculation of the nearest integer table index | |
| 61 | * -# Compute the fractional portion (fract) of the table index. | |
| 62 | * -# The final result equals <code>(1.0f-fract)*a + fract*b;</code> | |
| 63 | * | |
| 64 | * where | |
| 65 | * <pre> | |
| 66 | * b=Table[index+0]; | |
| 67 | * c=Table[index+1]; | |
| 68 | * </pre> | |
| 69 | */ | |
| 70 | ||
| 71 | /** | |
| 72 | * @addtogroup cos | |
| 73 | * @{ | |
| 74 | */ | |
| 75 | ||
| 76 | /** | |
| 77 | * @brief Fast approximation to the trigonometric cosine function for floating-point data. | |
| 78 | * @param[in] x input value in radians. | |
| 79 | * @return cos(x). | |
| 80 | */ | |
| 81 | ||
| 82 | float32_t arm_cos_f32( | |
| 83 | float32_t x) | |
| 84 | { | |
| 85 | float32_t cosVal, fract, in; /* Temporary variables for input, output */ | |
| 86 | uint16_t index; /* Index variable */ | |
| 87 | float32_t a, b; /* Two nearest output values */ | |
| 88 | int32_t n; | |
| 89 | float32_t findex; | |
| 90 | ||
| 91 | /* input x is in radians */ | |
| 92 | /* 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 */ | |
| 93 | in = x * 0.159154943092f + 0.25f; | |
| 94 | ||
| 95 | /* Calculation of floor value of input */ | |
| 96 | n = (int32_t) in; | |
| 97 | ||
| 98 | /* Make negative values towards -infinity */ | |
| 99 | if(in < 0.0f) | |
| 100 | { | |
| 101 | n--; | |
| 102 | } | |
| 103 | ||
| 104 | /* Map input value to [0 1] */ | |
| 105 | in = in - (float32_t) n; | |
| 106 | ||
| 107 | /* Calculation of index of the table */ | |
| 108 | findex = (float32_t) FAST_MATH_TABLE_SIZE * in; | |
| 109 | index = ((uint16_t)findex) & 0x1ff; | |
| 110 | ||
| 111 | /* fractional value calculation */ | |
| 112 | fract = findex - (float32_t) index; | |
| 113 | ||
| 114 | /* Read two nearest values of input value from the cos table */ | |
| 115 | a = sinTable_f32[index]; | |
| 116 | b = sinTable_f32[index+1]; | |
| 117 | ||
| 118 | /* Linear interpolation process */ | |
| 119 | cosVal = (1.0f-fract)*a + fract*b; | |
| 120 | ||
| 121 | /* Return the output value */ | |
| 122 | return (cosVal); | |
| 123 | } | |
| 124 | ||
| 125 | /** | |
| 126 | * @} end of cos group | |
| 127 | */ | |
