107 lines
2.9 KiB
C
107 lines
2.9 KiB
C
/* ----------------------------------------------------------------------
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* Project: CMSIS DSP Library
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* Title: arm_mean_q7.c
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* Description: Mean value of a Q7 vector
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*
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* $Date: 18. March 2019
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* $Revision: V1.6.0
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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) 2010-2019 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 Q7 vector.
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@param[in] pSrc points to the input vector
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@param[in] blockSize number of samples in input vector
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@param[out] pResult mean value returned here
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@return none
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@par Scaling and Overflow Behavior
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The function is implemented using a 32-bit internal
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accumulator. The input is represented in 1.7 format and is accumulated in a
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32-bit accumulator in 25.7 format. There is no risk of internal overflow with
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this approach, and the full precision of intermediate result is preserved.
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Finally, the accumulator is truncated to yield a result
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of 1.7 format.
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*/
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void arm_mean_q7(const q7_t *pSrc, uint32_t blockSize, q7_t *pResult) {
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uint32_t blkCnt; /* Loop counter */
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q31_t sum = 0; /* Temporary result storage */
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#if defined(ARM_MATH_LOOPUNROLL)
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q31_t in;
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#endif
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#if defined(ARM_MATH_LOOPUNROLL)
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/* Loop unrolling: Compute 4 outputs at a time */
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blkCnt = blockSize >> 2U;
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while (blkCnt > 0U) {
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/* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
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in = read_q7x4_ia((q7_t **)&pSrc);
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sum += ((in << 24U) >> 24U);
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sum += ((in << 16U) >> 24U);
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sum += ((in << 8U) >> 24U);
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sum += (in >> 24U);
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* Loop unrolling: Compute remaining outputs */
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blkCnt = blockSize % 0x4U;
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#else
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/* Initialize blkCnt with number of samples */
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blkCnt = blockSize;
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#endif /* #if defined (ARM_MATH_LOOPUNROLL) */
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while (blkCnt > 0U) {
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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 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 result to destination */
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*pResult = (q7_t)(sum / (int32_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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