| /* ---------------------------------------------------------------------- |
| * 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 |
| */ |