tmk_core/tool/mbed/mbed-sdk/libraries/dsp/cmsis_dsp/StatisticsFunctions/arm_mean_q15.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_q15.c
   9 *
  10 * Description:  Mean value of a Q15 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 Q15 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 32-bit internal accumulator.
  63  * The input is represented in 1.15 format and is accumulated in a 32-bit
  64  * accumulator in 17.15 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 saturated and truncated to yield a result of 1.15 format.
  68  *
  69  */
  70
  71
  72 void arm_mean_q15(
  73   q15_t * pSrc,
  74   uint32_t blockSize,
  75   q15_t * pResult)
  76 {
  77   q31_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 in;
  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     in = *__SIMD32(pSrc)++;
  94     sum += ((in << 16) >> 16);
  95     sum += (in >> 16);
  96     in = *__SIMD32(pSrc)++;
  97     sum += ((in << 16) >> 16);
  98     sum += (in >> 16);
  99
 100     /* Decrement the loop counter */
 101     blkCnt--;
 102   }
 103
 104   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
 105    ** No loop unrolling is used. */
 106   blkCnt = blockSize % 0x4u;
 107
 108 #else
 109
 110   /* Run the below code for Cortex-M0 */
 111
 112   /* Loop over blockSize number of values */
 113   blkCnt = blockSize;
 114
 115 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
 116
 117   while(blkCnt > 0u)
 118   {
 119     /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
 120     sum += *pSrc++;
 121
 122     /* Decrement the loop counter */
 123     blkCnt--;
 124   }
 125
 126   /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) / blockSize  */
 127   /* Store the result to the destination */
 128   *pResult = (q15_t) (sum / blockSize);
 129 }
 130
 131 /**
 132  * @} end of mean group
 133  */