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