tmk_core/tool/mbed/mbed-sdk/libraries/dsp/cmsis_dsp/StatisticsFunctions/arm_mean_q31.c

   1 /* ----------------------------------------------------------------------
   2 * Copyright (C) 2010-2013 ARM Limited. All rights reserved.
   3 *
   4 * $Date:        17. January 2013
   5 * $Revision:    V1.4.1
   6 *
   7 * Project:          CMSIS DSP Library
   8 * Title:                arm_mean_q31.c
   9 *
  10 * Description:  Mean value of a Q31 vector.
  11 *
  12 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
  13 *
  14 * Redistribution and use in source and binary forms, with or without
  15 * modification, are permitted provided that the following conditions
  16 * are met:
  17 *   - Redistributions of source code must retain the above copyright
  18 *     notice, this list of conditions and the following disclaimer.
  19 *   - Redistributions in binary form must reproduce the above copyright
  20 *     notice, this list of conditions and the following disclaimer in
  21 *     the documentation and/or other materials provided with the
  22 *     distribution.
  23 *   - Neither the name of ARM LIMITED nor the names of its contributors
  24 *     may be used to endorse or promote products derived from this
  25 *     software without specific prior written permission.
  26 *
  27 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  28 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  29 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  30 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  31 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  32 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  33 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  34 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  35 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  37 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  38 * POSSIBILITY OF SUCH DAMAGE.
  39 * -------------------------------------------------------------------- */
  40
  41 #include "arm_math.h"
  42
  43 /**
  44  * @ingroup groupStats
  45  */
  46
  47 /**
  48  * @addtogroup mean
  49  * @{
  50  */
  51
  52 /**
  53  * @brief Mean value of a Q31 vector.
  54  * @param[in]       *pSrc points to the input vector
  55  * @param[in]       blockSize length of the input vector
  56  * @param[out]      *pResult mean value returned here
  57  * @return none.
  58  *
  59  * @details
  60  * <b>Scaling and Overflow Behavior:</b>
  61  *\par
  62  * The function is implemented using a 64-bit internal accumulator.
  63  * The input is represented in 1.31 format and is accumulated in a 64-bit
  64  * accumulator in 33.31 format.
  65  * There is no risk of internal overflow with this approach, and the
  66  * full precision of intermediate result is preserved.
  67  * Finally, the accumulator is truncated to yield a result of 1.31 format.
  68  *
  69  */
  70
  71
  72 void arm_mean_q31(
  73   q31_t * pSrc,
  74   uint32_t blockSize,
  75   q31_t * pResult)
  76 {
  77   q63_t sum = 0;                                 /* Temporary result storage */
  78   uint32_t blkCnt;                               /* loop counter */
  79
  80 #ifndef ARM_MATH_CM0_FAMILY
  81
  82   /* Run the below code for Cortex-M4 and Cortex-M3 */
  83   q31_t in1, in2, in3, in4;
  84
  85   /*loop Unrolling */
  86   blkCnt = blockSize >> 2u;
  87
  88   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
  89    ** a second loop below computes the remaining 1 to 3 samples. */
  90   while(blkCnt > 0u)
  91   {
  92     /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
  93     in1 = *pSrc++;
  94     in2 = *pSrc++;
  95     in3 = *pSrc++;
  96     in4 = *pSrc++;
  97
  98     sum += in1;
  99     sum += in2;
 100     sum += in3;
 101     sum += in4;
 102
 103     /* Decrement the loop counter */
 104     blkCnt--;
 105   }
 106
 107   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
 108    ** No loop unrolling is used. */
 109   blkCnt = blockSize % 0x4u;
 110
 111 #else
 112
 113   /* Run the below code for Cortex-M0 */
 114
 115   /* Loop over blockSize number of values */
 116   blkCnt = blockSize;
 117
 118 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
 119
 120   while(blkCnt > 0u)
 121   {
 122     /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
 123     sum += *pSrc++;
 124
 125     /* Decrement the loop counter */
 126     blkCnt--;
 127   }
 128
 129   /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) / blockSize  */
 130   /* Store the result to the destination */
 131   *pResult = (q31_t) (sum / (int32_t) blockSize);
 132 }
 133
 134 /**
 135  * @} end of mean group
 136  */