lib/main/CMSIS/DSP/Source/StatisticsFunctions/arm_power_q7.c

   1 /* ----------------------------------------------------------------------
   2  * Project:      CMSIS DSP Library
   3  * Title:        arm_power_q7.c
   4  * Description:  Sum of the squares of the elements of a Q7 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 Q7 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 32-bit internal accumulator.
  52  * The input is represented in 1.7 format.
  53  * Intermediate multiplication yields a 2.14 format, and this
  54  * result is added without saturation to an accumulator in 18.14 format.
  55  * With 17 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 18.14 format.
  58  *
  59  */
  60
  61 void arm_power_q7(
  62   q7_t * pSrc,
  63   uint32_t blockSize,
  64   q31_t * pResult)
  65 {
  66   q31_t sum = 0;                                 /* Temporary result storage */
  67   q7_t in;                                       /* Temporary variable to store input */
  68   uint32_t blkCnt;                               /* loop counter */
  69
  70 #if defined (ARM_MATH_DSP)
  71   /* Run the below code for Cortex-M4 and Cortex-M3 */
  72
  73   q31_t input1;                                  /* Temporary variable to store packed input */
  74   q31_t in1, in2;                                /* Temporary variables to store input */
  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     /* Reading two inputs of pSrc vector and packing */
  84     input1 = *__SIMD32(pSrc)++;
  85
  86     in1 = __SXTB16(__ROR(input1, 8));
  87     in2 = __SXTB16(input1);
  88
  89     /* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */
  90     /* calculate power and accumulate to accumulator */
  91     sum = __SMLAD(in1, in1, sum);
  92     sum = __SMLAD(in2, in2, sum);
  93
  94     /* Decrement the loop counter */
  95     blkCnt--;
  96   }
  97
  98   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
  99    ** No loop unrolling is used. */
 100   blkCnt = blockSize % 0x4U;
 101
 102 #else
 103   /* Run the below code for Cortex-M0 */
 104
 105   /* Loop over blockSize number of values */
 106   blkCnt = blockSize;
 107
 108 #endif /* #if defined (ARM_MATH_DSP) */
 109
 110   while (blkCnt > 0U)
 111   {
 112     /* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */
 113     /* Compute Power and then store the result in a temporary variable, sum. */
 114     in = *pSrc++;
 115     sum += ((q15_t) in * in);
 116
 117     /* Decrement the loop counter */
 118     blkCnt--;
 119   }
 120
 121   /* Store the result in 18.14 format  */
 122   *pResult = sum;
 123 }
 124
 125 /**
 126  * @} end of power group
 127  */