lib/main/CMSIS/DSP/Source/StatisticsFunctions/arm_power_q15.c

   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  */