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  1. /* ----------------------------------------------------------------------
  2.  * Project:      CMSIS DSP Library
  3.  * Title:        arm_power_q15.c
  4.  * Description:  Sum of the squares of the elements of a Q15 vector
  5.  *
  6.  * $Date:        27. January 2017
  7.  * $Revision:    V.1.5.1
  8.  *
  9.  * Target Processor: Cortex-M cores
  10.  * -------------------------------------------------------------------- */
  11. /*
  12.  * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
  13.  *
  14.  * SPDX-License-Identifier: Apache-2.0
  15.  *
  16.  * Licensed under the Apache License, Version 2.0 (the License); you may
  17.  * not use this file except in compliance with the License.
  18.  * You may obtain a copy of the License at
  19.  *
  20.  * www.apache.org/licenses/LICENSE-2.0
  21.  *
  22.  * Unless required by applicable law or agreed to in writing, software
  23.  * distributed under the License is distributed on an AS IS BASIS, WITHOUT
  24.  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  25.  * See the License for the specific language governing permissions and
  26.  * limitations under the License.
  27.  */
  28.  
  29. #include "arm_math.h"
  30.  
  31. /**
  32.  * @ingroup groupStats
  33.  */
  34.  
  35. /**
  36.  * @addtogroup power
  37.  * @{
  38.  */
  39.  
  40. /**
  41.  * @brief Sum of the squares of the elements of a Q15 vector.
  42.  * @param[in]       *pSrc points to the input vector
  43.  * @param[in]       blockSize length of the input vector
  44.  * @param[out]      *pResult sum of the squares value returned here
  45.  * @return none.
  46.  *
  47.  * @details
  48.  * <b>Scaling and Overflow Behavior:</b>
  49.  *
  50.  * \par
  51.  * The function is implemented using a 64-bit internal accumulator.
  52.  * The input is represented in 1.15 format.
  53.  * Intermediate multiplication yields a 2.30 format, and this
  54.  * result is added without saturation to a 64-bit accumulator in 34.30 format.
  55.  * With 33 guard bits in the accumulator, there is no risk of overflow, and the
  56.  * full precision of the intermediate multiplication is preserved.
  57.  * Finally, the return result is in 34.30 format.
  58.  *
  59.  */
  60.  
  61. void arm_power_q15(
  62.   q15_t * pSrc,
  63.   uint32_t blockSize,
  64.   q63_t * pResult)
  65. {
  66.   q63_t sum = 0;                                 /* Temporary result storage */
  67.  
  68. #if defined (ARM_MATH_DSP)
  69.   /* Run the below code for Cortex-M4 and Cortex-M3 */
  70.  
  71.   q31_t in32;                                    /* Temporary variable to store input value */
  72.   q15_t in16;                                    /* Temporary variable to store input value */
  73.   uint32_t blkCnt;                               /* loop counter */
  74.  
  75.  
  76.   /* loop Unrolling */
  77.   blkCnt = blockSize >> 2U;
  78.  
  79.   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
  80.    ** a second loop below computes the remaining 1 to 3 samples. */
  81.   while (blkCnt > 0U)
  82.   {
  83.     /* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */
  84.     /* Compute Power and then store the result in a temporary variable, sum. */
  85.     in32 = *__SIMD32(pSrc)++;
  86.     sum = __SMLALD(in32, in32, sum);
  87.     in32 = *__SIMD32(pSrc)++;
  88.     sum = __SMLALD(in32, in32, sum);
  89.  
  90.     /* Decrement the loop counter */
  91.     blkCnt--;
  92.   }
  93.  
  94.   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
  95.    ** No loop unrolling is used. */
  96.   blkCnt = blockSize % 0x4U;
  97.  
  98.   while (blkCnt > 0U)
  99.   {
  100.     /* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */
  101.     /* Compute Power and then store the result in a temporary variable, sum. */
  102.     in16 = *pSrc++;
  103.     sum = __SMLALD(in16, in16, sum);
  104.  
  105.     /* Decrement the loop counter */
  106.     blkCnt--;
  107.   }
  108.  
  109. #else
  110.   /* Run the below code for Cortex-M0 */
  111.  
  112.   q15_t in;                                      /* Temporary variable to store input value */
  113.   uint32_t blkCnt;                               /* loop counter */
  114.  
  115.  
  116.   /* Loop over blockSize number of values */
  117.   blkCnt = blockSize;
  118.  
  119.   while (blkCnt > 0U)
  120.   {
  121.     /* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */
  122.     /* Compute Power and then store the result in a temporary variable, sum. */
  123.     in = *pSrc++;
  124.     sum += ((q31_t) in * in);
  125.  
  126.     /* Decrement the loop counter */
  127.     blkCnt--;
  128.   }
  129.  
  130. #endif /* #if defined (ARM_MATH_DSP) */
  131.  
  132.   /* Store the results in 34.30 format  */
  133.   *pResult = sum;
  134. }
  135.  
  136. /**
  137.  * @} end of power group
  138.  */
  139.