| /* ---------------------------------------------------------------------- |
| * Project: CMSIS DSP Library |
| * Title: arm_rms_q15.c |
| * Description: Root Mean Square of the elements of a Q15 vector |
| * |
| * $Date: 27. January 2017 |
| * $Revision: V.1.5.1 |
| * |
| * Target Processor: Cortex-M cores |
| * -------------------------------------------------------------------- */ |
| /* |
| * Copyright (C) 2010-2017 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" |
| |
| /** |
| * @addtogroup RMS |
| * @{ |
| */ |
| |
| /** |
| * @brief Root Mean Square of the elements of a Q15 vector. |
| * @param[in] *pSrc points to the input vector |
| * @param[in] blockSize length of the input vector |
| * @param[out] *pResult rms value returned here |
| * @return none. |
| * |
| * @details |
| * <b>Scaling and Overflow Behavior:</b> |
| * |
| * \par |
| * The function is implemented using a 64-bit internal accumulator. |
| * The input is represented in 1.15 format. |
| * Intermediate multiplication yields a 2.30 format, and this |
| * result is added without saturation to a 64-bit accumulator in 34.30 format. |
| * With 33 guard bits in the accumulator, there is no risk of overflow, and the |
| * full precision of the intermediate multiplication is preserved. |
| * Finally, the 34.30 result is truncated to 34.15 format by discarding the lower |
| * 15 bits, and then saturated to yield a result in 1.15 format. |
| * |
| */ |
| |
| void arm_rms_q15( |
| q15_t * pSrc, |
| uint32_t blockSize, |
| q15_t * pResult) |
| { |
| q63_t sum = 0; /* accumulator */ |
| |
| #if defined (ARM_MATH_DSP) |
| /* Run the below code for Cortex-M4 and Cortex-M3 */ |
| |
| q31_t in; /* temporary variable to store the input value */ |
| q15_t in1; /* temporary variable to store the input value */ |
| uint32_t blkCnt; /* loop counter */ |
| |
| /* loop Unrolling */ |
| blkCnt = blockSize >> 2U; |
| |
| /* First part of the processing with loop unrolling. Compute 4 outputs at a time. |
| ** a second loop below computes the remaining 1 to 3 samples. */ |
| while (blkCnt > 0U) |
| { |
| /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */ |
| /* Compute sum of the squares and then store the results in a temporary variable, sum */ |
| in = *__SIMD32(pSrc)++; |
| sum = __SMLALD(in, in, sum); |
| in = *__SIMD32(pSrc)++; |
| sum = __SMLALD(in, in, sum); |
| |
| /* Decrement the loop counter */ |
| blkCnt--; |
| } |
| |
| /* If the blockSize is not a multiple of 4, compute any remaining output samples here. |
| ** No loop unrolling is used. */ |
| blkCnt = blockSize % 0x4U; |
| |
| while (blkCnt > 0U) |
| { |
| /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */ |
| /* Compute sum of the squares and then store the results in a temporary variable, sum */ |
| in1 = *pSrc++; |
| sum = __SMLALD(in1, in1, sum); |
| |
| /* Decrement the loop counter */ |
| blkCnt--; |
| } |
| |
| /* Truncating and saturating the accumulator to 1.15 format */ |
| /* Store the result in the destination */ |
| arm_sqrt_q15(__SSAT((sum / (q63_t)blockSize) >> 15, 16), pResult); |
| |
| #else |
| /* Run the below code for Cortex-M0 */ |
| |
| q15_t in; /* temporary variable to store the input value */ |
| uint32_t blkCnt; /* loop counter */ |
| |
| /* Loop over blockSize number of values */ |
| blkCnt = blockSize; |
| |
| while (blkCnt > 0U) |
| { |
| /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */ |
| /* Compute sum of the squares and then store the results in a temporary variable, sum */ |
| in = *pSrc++; |
| sum += ((q31_t) in * in); |
| |
| /* Decrement the loop counter */ |
| blkCnt--; |
| } |
| |
| /* Truncating and saturating the accumulator to 1.15 format */ |
| /* Store the result in the destination */ |
| arm_sqrt_q15(__SSAT((sum / (q63_t)blockSize) >> 15, 16), pResult); |
| |
| #endif /* #if defined (ARM_MATH_DSP) */ |
| |
| } |
| |
| /** |
| * @} end of RMS group |
| */ |