115 lines
3.1 KiB
C
115 lines
3.1 KiB
C
|
/* ----------------------------------------------------------------------
|
||
|
|
* Project: CMSIS DSP Library
|
||
|
|
* Title: arm_mean_q15.c
|
||
|
|
* Description: Mean value of a Q15 vector
|
||
|
|
*
|
||
|
|
* $Date: 18. March 2019
|
||
|
|
* $Revision: V1.6.0
|
||
|
|
*
|
||
|
|
* Target Processor: Cortex-M cores
|
||
|
|
* -------------------------------------------------------------------- */
|
||
|
|
/*
|
||
|
|
* Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved.
|
||
|
|
*
|
||
|
|
* SPDX-License-Identifier: Apache-2.0
|
||
|
|
*
|
||
|
|
* Licensed under the Apache License, Version 2.0 (the License); you may
|
||
|
|
* not use this file except in compliance with the License.
|
||
|
|
* You may obtain a copy of the License at
|
||
|
|
*
|
||
|
|
* www.apache.org/licenses/LICENSE-2.0
|
||
|
|
*
|
||
|
|
* Unless required by applicable law or agreed to in writing, software
|
||
|
|
* distributed under the License is distributed on an AS IS BASIS, WITHOUT
|
||
|
|
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
||
|
|
* See the License for the specific language governing permissions and
|
||
|
|
* limitations under the License.
|
||
|
|
*/
|
||
|
|
|
||
|
|
#include "arm_math.h"
|
||
|
|
|
||
|
|
/**
|
||
|
|
@ingroup groupStats
|
||
|
|
*/
|
||
|
|
|
||
|
|
/**
|
||
|
|
@addtogroup mean
|
||
|
|
@{
|
||
|
|
*/
|
||
|
|
|
||
|
|
/**
|
||
|
|
@brief Mean value of a Q15 vector.
|
||
|
|
@param[in] pSrc points to the input vector
|
||
|
|
@param[in] blockSize number of samples in input vector
|
||
|
|
@param[out] pResult mean value returned here
|
||
|
|
@return none
|
||
|
|
|
||
|
|
@par Scaling and Overflow Behavior
|
||
|
|
The function is implemented using a 32-bit internal accumulator.
|
||
|
|
The input is represented in 1.15 format and is accumulated in a 32-bit
|
||
|
|
accumulator in 17.15 format.
|
||
|
|
There is no risk of internal overflow with this approach, and the
|
||
|
|
full precision of intermediate result is preserved.
|
||
|
|
Finally, the accumulator is truncated to yield a result of 1.15 format.
|
||
|
|
*/
|
||
|
|
|
||
|
|
void arm_mean_q15(
|
||
|
|
const q15_t * pSrc,
|
||
|
|
uint32_t blockSize,
|
||
|
|
q15_t * pResult)
|
||
|
|
{
|
||
|
|
uint32_t blkCnt; /* Loop counter */
|
||
|
|
q31_t sum = 0; /* Temporary result storage */
|
||
|
|
|
||
|
|
#if defined (ARM_MATH_LOOPUNROLL)
|
||
|
|
q31_t in;
|
||
|
|
#endif
|
||
|
|
|
||
|
|
#if defined (ARM_MATH_LOOPUNROLL)
|
||
|
|
|
||
|
|
/* Loop unrolling: Compute 4 outputs at a time */
|
||
|
|
blkCnt = blockSize >> 2U;
|
||
|
|
|
||
|
|
while (blkCnt > 0U)
|
||
|
|
{
|
||
|
|
/* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
|
||
|
|
in = read_q15x2_ia ((q15_t **) &pSrc);
|
||
|
|
sum += ((in << 16U) >> 16U);
|
||
|
|
sum += (in >> 16U);
|
||
|
|
|
||
|
|
in = read_q15x2_ia ((q15_t **) &pSrc);
|
||
|
|
sum += ((in << 16U) >> 16U);
|
||
|
|
sum += (in >> 16U);
|
||
|
|
|
||
|
|
/* Decrement the loop counter */
|
||
|
|
blkCnt--;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Loop unrolling: Compute remaining outputs */
|
||
|
|
blkCnt = blockSize % 0x4U;
|
||
|
|
|
||
|
|
#else
|
||
|
|
|
||
|
|
/* Initialize blkCnt with number of samples */
|
||
|
|
blkCnt = blockSize;
|
||
|
|
|
||
|
|
#endif /* #if defined (ARM_MATH_LOOPUNROLL) */
|
||
|
|
|
||
|
|
while (blkCnt > 0U)
|
||
|
|
{
|
||
|
|
/* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
|
||
|
|
sum += *pSrc++;
|
||
|
|
|
||
|
|
/* Decrement loop counter */
|
||
|
|
blkCnt--;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) / blockSize */
|
||
|
|
/* Store result to destination */
|
||
|
|
*pResult = (q15_t) (sum / (int32_t) blockSize);
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
@} end of mean group
|
||
|
|
*/
|