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121 lines
3.2 KiB
121 lines
3.2 KiB
3 years ago
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/* ----------------------------------------------------------------------
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* Project: CMSIS DSP Library
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* Title: arm_mean_q15.c
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* Description: Mean value of a Q15 vector
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*
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* $Date: 27. January 2017
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* $Revision: V.1.5.1
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*
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* Target Processor: Cortex-M cores
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* -------------------------------------------------------------------- */
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/*
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* Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the License); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an AS IS BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "arm_math.h"
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/**
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* @ingroup groupStats
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*/
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/**
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* @addtogroup mean
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* @{
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*/
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/**
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* @brief Mean value of a Q15 vector.
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* @param[in] *pSrc points to the input vector
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* @param[in] blockSize length of the input vector
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* @param[out] *pResult mean value returned here
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* @return none.
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*
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* @details
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* <b>Scaling and Overflow Behavior:</b>
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* \par
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* The function is implemented using a 32-bit internal accumulator.
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* The input is represented in 1.15 format and is accumulated in a 32-bit
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* accumulator in 17.15 format.
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* There is no risk of internal overflow with this approach, and the
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* full precision of intermediate result is preserved.
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* Finally, the accumulator is saturated and truncated to yield a result of 1.15 format.
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*
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*/
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void arm_mean_q15(
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q15_t * pSrc,
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uint32_t blockSize,
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q15_t * pResult)
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{
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q31_t sum = 0; /* Temporary result storage */
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uint32_t blkCnt; /* loop counter */
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#if defined (ARM_MATH_DSP)
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/* Run the below code for Cortex-M4 and Cortex-M3 */
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q31_t in;
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/*loop Unrolling */
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blkCnt = blockSize >> 2U;
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/* First part of the processing with loop unrolling. Compute 4 outputs at a time.
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** a second loop below computes the remaining 1 to 3 samples. */
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while (blkCnt > 0U)
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{
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/* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
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in = *__SIMD32(pSrc)++;
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sum += ((in << 16U) >> 16U);
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sum += (in >> 16U);
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in = *__SIMD32(pSrc)++;
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sum += ((in << 16U) >> 16U);
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sum += (in >> 16U);
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
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** No loop unrolling is used. */
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blkCnt = blockSize % 0x4U;
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#else
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/* Run the below code for Cortex-M0 */
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/* Loop over blockSize number of values */
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blkCnt = blockSize;
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#endif /* #if defined (ARM_MATH_DSP) */
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while (blkCnt > 0U)
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{
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/* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
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sum += *pSrc++;
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) / blockSize */
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/* Store the result to the destination */
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*pResult = (q15_t) (sum / (q31_t)blockSize);
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}
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/**
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* @} end of mean group
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*/
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