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142 lines
4.3 KiB
C
142 lines
4.3 KiB
C
/* ----------------------------------------------------------------------
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* Project: CMSIS DSP Library
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* Title: arm_rms_q31.c
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* Description: Root Mean Square of the elements of a Q31 vector
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*
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* $Date: 23 April 2021
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* $Revision: V1.9.0
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*
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* Target Processor: Cortex-M and Cortex-A cores
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* -------------------------------------------------------------------- */
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/*
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* Copyright (C) 2010-2021 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 "dsp/statistics_functions.h"
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/**
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@ingroup groupStats
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*/
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/**
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@addtogroup RMS
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@{
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*/
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/**
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@brief Root Mean Square of the elements of a Q31 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 root mean square 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 an internal 64-bit accumulator.
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The input is represented in 1.31 format, and intermediate multiplication
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yields a 2.62 format.
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The accumulator maintains full precision of the intermediate multiplication results,
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but provides only a single guard bit.
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There is no saturation on intermediate additions.
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If the accumulator overflows, it wraps around and distorts the result.
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In order to avoid overflows completely, the input signal must be scaled down by
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log2(blockSize) bits, as a total of blockSize additions are performed internally.
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Finally, the 2.62 accumulator is right shifted by 31 bits to yield a 1.31 format value.
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*/
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#if defined(ARM_MATH_MVEI) && !defined(ARM_MATH_AUTOVECTORIZE)
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void arm_rms_q31(
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const q31_t * pSrc,
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uint32_t blockSize,
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q31_t * pResult)
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{
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q63_t pow = 0.0f;
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q31_t normalizedPower;
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arm_power_q31(pSrc, blockSize, &pow);
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normalizedPower=clip_q63_to_q31((pow / (q63_t) blockSize) >> 17);
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arm_sqrt_q31(normalizedPower, pResult);
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}
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#else
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void arm_rms_q31(
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const q31_t * pSrc,
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uint32_t blockSize,
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q31_t * pResult)
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{
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uint32_t blkCnt; /* Loop counter */
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uint64_t sum = 0; /* Temporary result storage (can get never negative. changed type from q63 to uint64 */
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q31_t in; /* Temporary variable to store input value */
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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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{
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/* C = A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1] */
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in = *pSrc++;
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/* Compute sum of squares and store result in a temporary variable, sum. */
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sum += ((q63_t) in * in);
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in = *pSrc++;
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sum += ((q63_t) in * in);
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in = *pSrc++;
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sum += ((q63_t) in * in);
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in = *pSrc++;
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sum += ((q63_t) in * in);
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/* Decrement 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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{
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/* C = A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1] */
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in = *pSrc++;
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/* Compute sum of squares and store result in a temporary variable. */
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sum += ((q63_t) in * in);
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/* Decrement loop counter */
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blkCnt--;
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}
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/* Convert data in 2.62 to 1.31 by 31 right shifts and saturate */
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/* Compute Rms and store result in destination vector */
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arm_sqrt_q31(clip_q63_to_q31((sum / (q63_t) blockSize) >> 31), pResult);
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}
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#endif /* defined(ARM_MATH_MVEI) */
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/**
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@} end of RMS group
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*/
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