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git.gir.st - tmk_keyboard.git/blob - tmk_core/tool/mbed/mbed-sdk/libraries/dsp/cmsis_dsp/StatisticsFunctions/arm_power_q31.c
1 /* ----------------------------------------------------------------------
2 * Copyright (C) 2010-2013 ARM Limited. All rights reserved.
4 * $Date: 17. January 2013
7 * Project: CMSIS DSP Library
8 * Title: arm_power_q31.c
10 * Description: Sum of the squares of the elements of a Q31 vector.
12 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions
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
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.
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 * -------------------------------------------------------------------- */
53 * @brief Sum of the squares of the elements of a Q31 vector.
54 * @param[in] *pSrc points to the input vector
55 * @param[in] blockSize length of the input vector
56 * @param[out] *pResult sum of the squares value returned here
60 * <b>Scaling and Overflow Behavior:</b>
63 * The function is implemented using a 64-bit internal accumulator.
64 * The input is represented in 1.31 format.
65 * Intermediate multiplication yields a 2.62 format, and this
66 * result is truncated to 2.48 format by discarding the lower 14 bits.
67 * The 2.48 result is then added without saturation to a 64-bit accumulator in 16.48 format.
68 * With 15 guard bits in the accumulator, there is no risk of overflow, and the
69 * full precision of the intermediate multiplication is preserved.
70 * Finally, the return result is in 16.48 format.
79 q63_t sum
= 0 ; /* Temporary result storage */
81 uint32_t blkCnt
; /* loop counter */
84 #ifndef ARM_MATH_CM0_FAMILY
86 /* Run the below code for Cortex-M4 and Cortex-M3 */
89 blkCnt
= blockSize
>> 2u ;
91 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
92 ** a second loop below computes the remaining 1 to 3 samples. */
95 /* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */
96 /* Compute Power then shift intermediate results by 14 bits to maintain 16.48 format and then store the result in a temporary variable sum, providing 15 guard bits. */
98 sum
+= (( q63_t
) in
* in
) >> 14u ;
101 sum
+= (( q63_t
) in
* in
) >> 14u ;
104 sum
+= (( q63_t
) in
* in
) >> 14u ;
107 sum
+= (( q63_t
) in
* in
) >> 14u ;
109 /* Decrement the loop counter */
113 /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
114 ** No loop unrolling is used. */
115 blkCnt
= blockSize
% 0x4 u
;
119 /* Run the below code for Cortex-M0 */
121 /* Loop over blockSize number of values */
124 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
128 /* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */
129 /* Compute Power and then store the result in a temporary variable, sum. */
131 sum
+= (( q63_t
) in
* in
) >> 14u ;
133 /* Decrement the loop counter */
137 /* Store the results in 16.48 format */
142 * @} end of power group