Joep D / CMSIS_DSP_5

The CMSIS DSP 5 library

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functions/StatisticsFunctions/arm_mean_q15.c@3:4098b9d3d571, 2018-06-21 (annotated)

Committer:
xorjoep
Date:
Thu Jun 21 11:56:27 2018 +0000
Revision:
3:4098b9d3d571
Parent:
1:24714b45cd1b 
headers is a folder not a library

Who changed what in which revision?

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xorjoep 1:24714b45cd1b 1 /* ----------------------------------------------------------------------
xorjoep 1:24714b45cd1b 2 * Project: CMSIS DSP Library
xorjoep 1:24714b45cd1b 3 * Title: arm_mean_q15.c
xorjoep 1:24714b45cd1b 4 * Description: Mean value of a Q15 vector
xorjoep 1:24714b45cd1b 5 *
xorjoep 1:24714b45cd1b 6 * $Date: 27. January 2017
xorjoep 1:24714b45cd1b 7 * $Revision: V.1.5.1
xorjoep 1:24714b45cd1b 8 *
xorjoep 1:24714b45cd1b 9 * Target Processor: Cortex-M cores
xorjoep 1:24714b45cd1b 10 * -------------------------------------------------------------------- */
xorjoep 1:24714b45cd1b 11 /*
xorjoep 1:24714b45cd1b 12 * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
xorjoep 1:24714b45cd1b 13 *
xorjoep 1:24714b45cd1b 14 * SPDX-License-Identifier: Apache-2.0
xorjoep 1:24714b45cd1b 15 *
xorjoep 1:24714b45cd1b 16 * Licensed under the Apache License, Version 2.0 (the License); you may
xorjoep 1:24714b45cd1b 17 * not use this file except in compliance with the License.
xorjoep 1:24714b45cd1b 18 * You may obtain a copy of the License at
xorjoep 1:24714b45cd1b 19 *
xorjoep 1:24714b45cd1b 20 * www.apache.org/licenses/LICENSE-2.0
xorjoep 1:24714b45cd1b 21 *
xorjoep 1:24714b45cd1b 22 * Unless required by applicable law or agreed to in writing, software
xorjoep 1:24714b45cd1b 23 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
xorjoep 1:24714b45cd1b 24 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
xorjoep 1:24714b45cd1b 25 * See the License for the specific language governing permissions and
xorjoep 1:24714b45cd1b 26 * limitations under the License.
xorjoep 1:24714b45cd1b 27 */
xorjoep 1:24714b45cd1b 28
xorjoep 1:24714b45cd1b 29 #include "arm_math.h"
xorjoep 1:24714b45cd1b 30
xorjoep 1:24714b45cd1b 31 /**
xorjoep 1:24714b45cd1b 32 * @ingroup groupStats
xorjoep 1:24714b45cd1b 33 */
xorjoep 1:24714b45cd1b 34
xorjoep 1:24714b45cd1b 35 /**
xorjoep 1:24714b45cd1b 36 * @addtogroup mean
xorjoep 1:24714b45cd1b 37 * @{
xorjoep 1:24714b45cd1b 38 */
xorjoep 1:24714b45cd1b 39
xorjoep 1:24714b45cd1b 40
xorjoep 1:24714b45cd1b 41 /**
xorjoep 1:24714b45cd1b 42 * @brief Mean value of a Q15 vector.
xorjoep 1:24714b45cd1b 43 * @param[in] *pSrc points to the input vector
xorjoep 1:24714b45cd1b 44 * @param[in] blockSize length of the input vector
xorjoep 1:24714b45cd1b 45 * @param[out] *pResult mean value returned here
xorjoep 1:24714b45cd1b 46 * @return none.
xorjoep 1:24714b45cd1b 47 *
xorjoep 1:24714b45cd1b 48 * @details
xorjoep 1:24714b45cd1b 49 * <b>Scaling and Overflow Behavior:</b>
xorjoep 1:24714b45cd1b 50 * \par
xorjoep 1:24714b45cd1b 51 * The function is implemented using a 32-bit internal accumulator.
xorjoep 1:24714b45cd1b 52 * The input is represented in 1.15 format and is accumulated in a 32-bit
xorjoep 1:24714b45cd1b 53 * accumulator in 17.15 format.
xorjoep 1:24714b45cd1b 54 * There is no risk of internal overflow with this approach, and the
xorjoep 1:24714b45cd1b 55 * full precision of intermediate result is preserved.
xorjoep 1:24714b45cd1b 56 * Finally, the accumulator is saturated and truncated to yield a result of 1.15 format.
xorjoep 1:24714b45cd1b 57 *
xorjoep 1:24714b45cd1b 58 */
xorjoep 1:24714b45cd1b 59
xorjoep 1:24714b45cd1b 60 void arm_mean_q15(
xorjoep 1:24714b45cd1b 61 q15_t * pSrc,
xorjoep 1:24714b45cd1b 62 uint32_t blockSize,
xorjoep 1:24714b45cd1b 63 q15_t * pResult)
xorjoep 1:24714b45cd1b 64 {
xorjoep 1:24714b45cd1b 65 q31_t sum = 0; /* Temporary result storage */
xorjoep 1:24714b45cd1b 66 uint32_t blkCnt; /* loop counter */
xorjoep 1:24714b45cd1b 67
xorjoep 1:24714b45cd1b 68 #if defined (ARM_MATH_DSP)
xorjoep 1:24714b45cd1b 69 /* Run the below code for Cortex-M4 and Cortex-M3 */
xorjoep 1:24714b45cd1b 70
xorjoep 1:24714b45cd1b 71 q31_t in;
xorjoep 1:24714b45cd1b 72
xorjoep 1:24714b45cd1b 73 /*loop Unrolling */
xorjoep 1:24714b45cd1b 74 blkCnt = blockSize >> 2U;
xorjoep 1:24714b45cd1b 75
xorjoep 1:24714b45cd1b 76 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
xorjoep 1:24714b45cd1b 77 ** a second loop below computes the remaining 1 to 3 samples. */
xorjoep 1:24714b45cd1b 78 while (blkCnt > 0U)
xorjoep 1:24714b45cd1b 79 {
xorjoep 1:24714b45cd1b 80 /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
xorjoep 1:24714b45cd1b 81 in = *__SIMD32(pSrc)++;
xorjoep 1:24714b45cd1b 82 sum += ((in << 16U) >> 16U);
xorjoep 1:24714b45cd1b 83 sum += (in >> 16U);
xorjoep 1:24714b45cd1b 84 in = *__SIMD32(pSrc)++;
xorjoep 1:24714b45cd1b 85 sum += ((in << 16U) >> 16U);
xorjoep 1:24714b45cd1b 86 sum += (in >> 16U);
xorjoep 1:24714b45cd1b 87
xorjoep 1:24714b45cd1b 88 /* Decrement the loop counter */
xorjoep 1:24714b45cd1b 89 blkCnt--;
xorjoep 1:24714b45cd1b 90 }
xorjoep 1:24714b45cd1b 91
xorjoep 1:24714b45cd1b 92 /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
xorjoep 1:24714b45cd1b 93 ** No loop unrolling is used. */
xorjoep 1:24714b45cd1b 94 blkCnt = blockSize % 0x4U;
xorjoep 1:24714b45cd1b 95
xorjoep 1:24714b45cd1b 96 #else
xorjoep 1:24714b45cd1b 97 /* Run the below code for Cortex-M0 */
xorjoep 1:24714b45cd1b 98
xorjoep 1:24714b45cd1b 99 /* Loop over blockSize number of values */
xorjoep 1:24714b45cd1b 100 blkCnt = blockSize;
xorjoep 1:24714b45cd1b 101
xorjoep 1:24714b45cd1b 102 #endif /* #if defined (ARM_MATH_DSP) */
xorjoep 1:24714b45cd1b 103
xorjoep 1:24714b45cd1b 104 while (blkCnt > 0U)
xorjoep 1:24714b45cd1b 105 {
xorjoep 1:24714b45cd1b 106 /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
xorjoep 1:24714b45cd1b 107 sum += *pSrc++;
xorjoep 1:24714b45cd1b 108
xorjoep 1:24714b45cd1b 109 /* Decrement the loop counter */
xorjoep 1:24714b45cd1b 110 blkCnt--;
xorjoep 1:24714b45cd1b 111 }
xorjoep 1:24714b45cd1b 112
xorjoep 1:24714b45cd1b 113 /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) / blockSize */
xorjoep 1:24714b45cd1b 114 /* Store the result to the destination */
xorjoep 1:24714b45cd1b 115 *pResult = (q15_t) (sum / (q31_t)blockSize);
xorjoep 1:24714b45cd1b 116 }
xorjoep 1:24714b45cd1b 117
xorjoep 1:24714b45cd1b 118 /**
xorjoep 1:24714b45cd1b 119 * @} end of mean group
xorjoep 1:24714b45cd1b 120 */