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comparison f103c8/Drivers/CMSIS/DSP_Lib/Source/FastMathFunctions/arm_sqrt_q31.c @ 2:0c59e7a7782a

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Working on GPIO and RCC
author cin
date Mon, 16 Jan 2017 11:04:47 +0300
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1:a0b14b11ad9f 2:0c59e7a7782a
1 /* ----------------------------------------------------------------------
2 * Copyright (C) 2010-2014 ARM Limited. All rights reserved.
3 *
4 * $Date: 19. October 2015
5 * $Revision: V.1.4.5 a
6 *
7 * Project: CMSIS DSP Library
8 * Title: arm_sqrt_q31.c
9 *
10 * Description: Q31 square root function.
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 #include "arm_math.h"
41 #include "arm_common_tables.h"
42
43 /**
44 * @ingroup groupFastMath
45 */
46
47 /**
48 * @addtogroup SQRT
49 * @{
50 */
51
52 /**
53 * @brief Q31 square root function.
54 * @param[in] in input value. The range of the input value is [0 +1) or 0x00000000 to 0x7FFFFFFF.
55 * @param[out] *pOut square root of input value.
56 * @return The function returns ARM_MATH_SUCCESS if the input value is positive
57 * and ARM_MATH_ARGUMENT_ERROR if the input is negative. For
58 * negative inputs, the function returns *pOut = 0.
59 */
60
61 arm_status arm_sqrt_q31(
62 q31_t in,
63 q31_t * pOut)
64 {
65 q31_t number, temp1, bits_val1, var1, signBits1, half;
66 float32_t temp_float1;
67 union
68 {
69 q31_t fracval;
70 float32_t floatval;
71 } tempconv;
72
73 number = in;
74
75 /* If the input is a positive number then compute the signBits. */
76 if(number > 0)
77 {
78 signBits1 = __CLZ(number) - 1;
79
80 /* Shift by the number of signBits1 */
81 if((signBits1 % 2) == 0)
82 {
83 number = number << signBits1;
84 }
85 else
86 {
87 number = number << (signBits1 - 1);
88 }
89
90 /* Calculate half value of the number */
91 half = number >> 1;
92 /* Store the number for later use */
93 temp1 = number;
94
95 /*Convert to float */
96 temp_float1 = number * 4.6566128731e-010f;
97 /*Store as integer */
98 tempconv.floatval = temp_float1;
99 bits_val1 = tempconv.fracval;
100 /* Subtract the shifted value from the magic number to give intial guess */
101 bits_val1 = 0x5f3759df - (bits_val1 >> 1); /* gives initial guess */
102 /* Store as float */
103 tempconv.fracval = bits_val1;
104 temp_float1 = tempconv.floatval;
105 /* Convert to integer format */
106 var1 = (q31_t) (temp_float1 * 1073741824);
107
108 /* 1st iteration */
109 var1 = ((q31_t) ((q63_t) var1 * (0x30000000 -
110 ((q31_t)
111 ((((q31_t)
112 (((q63_t) var1 * var1) >> 31)) *
113 (q63_t) half) >> 31))) >> 31)) << 2;
114 /* 2nd iteration */
115 var1 = ((q31_t) ((q63_t) var1 * (0x30000000 -
116 ((q31_t)
117 ((((q31_t)
118 (((q63_t) var1 * var1) >> 31)) *
119 (q63_t) half) >> 31))) >> 31)) << 2;
120 /* 3rd iteration */
121 var1 = ((q31_t) ((q63_t) var1 * (0x30000000 -
122 ((q31_t)
123 ((((q31_t)
124 (((q63_t) var1 * var1) >> 31)) *
125 (q63_t) half) >> 31))) >> 31)) << 2;
126
127 /* Multiply the inverse square root with the original value */
128 var1 = ((q31_t) (((q63_t) temp1 * var1) >> 31)) << 1;
129
130 /* Shift the output down accordingly */
131 if((signBits1 % 2) == 0)
132 {
133 var1 = var1 >> (signBits1 / 2);
134 }
135 else
136 {
137 var1 = var1 >> ((signBits1 - 1) / 2);
138 }
139 *pOut = var1;
140
141 return (ARM_MATH_SUCCESS);
142 }
143 /* If the number is a negative number then store zero as its square root value */
144 else
145 {
146 *pOut = 0;
147 return (ARM_MATH_ARGUMENT_ERROR);
148 }
149 }
150
151 /**
152 * @} end of SQRT group
153 */