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git.gir.st - tmk_keyboard.git/blob - tmk_core/tool/mbed/mbed-sdk/libraries/dsp/cmsis_dsp/StatisticsFunctions/arm_mean_q15.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_mean_q15.c
10 * Description: Mean value of a Q15 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 Mean value of a Q15 vector.
54 * @param[in] *pSrc points to the input vector
55 * @param[in] blockSize length of the input vector
56 * @param[out] *pResult mean value returned here
60 * <b>Scaling and Overflow Behavior:</b>
62 * The function is implemented using a 32-bit internal accumulator.
63 * The input is represented in 1.15 format and is accumulated in a 32-bit
64 * accumulator in 17.15 format.
65 * There is no risk of internal overflow with this approach, and the
66 * full precision of intermediate result is preserved.
67 * Finally, the accumulator is saturated and truncated to yield a result of 1.15 format.
77 q31_t sum
= 0; /* Temporary result storage */
78 uint32_t blkCnt
; /* loop counter */
80 #ifndef ARM_MATH_CM0_FAMILY
82 /* Run the below code for Cortex-M4 and Cortex-M3 */
86 blkCnt
= blockSize
>> 2u;
88 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
89 ** a second loop below computes the remaining 1 to 3 samples. */
92 /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
93 in
= *__SIMD32(pSrc
)++;
94 sum
+= ((in
<< 16) >> 16);
96 in
= *__SIMD32(pSrc
)++;
97 sum
+= ((in
<< 16) >> 16);
100 /* Decrement the loop counter */
104 /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
105 ** No loop unrolling is used. */
106 blkCnt
= blockSize
% 0x4u
;
110 /* Run the below code for Cortex-M0 */
112 /* Loop over blockSize number of values */
115 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
119 /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
122 /* Decrement the loop counter */
126 /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) / blockSize */
127 /* Store the result to the destination */
128 *pResult
= (q15_t
) (sum
/ blockSize
);
132 * @} end of mean group