text: /* ----------------------------------------------------------------------    
  * Copyright (C) 2010-2014 ARM Limited. All rights reserved.    
  *    
  * $Date:        19. March 2015
  * $Revision: 	V.1.4.5  
  *    
  * Project: 	    CMSIS DSP Library    
  * Title:		arm_mean_q15.c    
  *    
  * Description:	Mean value of a Q15 vector.   
  *    
  * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
  *  
  * Redistribution and use in source and binary forms, with or without 
  * modification, are permitted provided that the following conditions
  * are met:
  *   - Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  *   - Redistributions in binary form must reproduce the above copyright
  *     notice, this list of conditions and the following disclaimer in
  *     the documentation and/or other materials provided with the 
  *     distribution.
  *   - Neither the name of ARM LIMITED nor the names of its contributors
  *     may be used to endorse or promote products derived from this
  *     software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 
  * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  * POSSIBILITY OF SUCH DAMAGE.   
  * -------------------------------------------------------------------- */
  
  #include "../../../../../drivers/CMSIS/Include/arm_math.h"
  
  /**    
   * @ingroup groupStats    
   */
  
  /**    
   * @addtogroup mean    
   * @{    
   */
  
  /**    
   * @brief Mean value of a Q15 vector.    
   * @param[in]       *pSrc points to the input vector    
   * @param[in]       blockSize length of the input vector    
   * @param[out]      *pResult mean value returned here    
   * @return none.    
   *    
   * @details    
   * <b>Scaling and Overflow Behavior:</b>    
   * \par    
   * The function is implemented using a 32-bit internal accumulator.    
   * The input is represented in 1.15 format and is accumulated in a 32-bit     
   * accumulator in 17.15 format.     
   * There is no risk of internal overflow with this approach, and the     
   * full precision of intermediate result is preserved.     
   * Finally, the accumulator is saturated and truncated to yield a result of 1.15 format.    
   *    
   */
  
  
  void arm_mean_q15(
    q15_t * pSrc,
    uint32_t blockSize,
    q15_t * pResult)
  {
    q31_t sum = 0;                                 /* Temporary result storage */
    uint32_t blkCnt;                               /* loop counter */
  
  #ifndef ARM_MATH_CM0_FAMILY
  
    /* Run the below code for Cortex-M4 and Cortex-M3 */
    q31_t in;
  
    /*loop Unrolling */
    blkCnt = blockSize >> 2u;
  
    /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.    
     ** a second loop below computes the remaining 1 to 3 samples. */
    while(blkCnt > 0u)
    {
      /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
      in = *__SIMD32(pSrc)++;
      sum += ((in << 16) >> 16);
      sum += (in >> 16);
      in = *__SIMD32(pSrc)++;
      sum += ((in << 16) >> 16);
      sum += (in >> 16);
  
      /* Decrement the loop counter */
      blkCnt--;
    }
  
    /* If the blockSize is not a multiple of 4, compute any remaining output samples here.    
     ** No loop unrolling is used. */
    blkCnt = blockSize % 0x4u;
  
  #else
  
    /* Run the below code for Cortex-M0 */
  
    /* Loop over blockSize number of values */
    blkCnt = blockSize;
  
  #endif /* #ifndef ARM_MATH_CM0_FAMILY */
  
    while(blkCnt > 0u)
    {
      /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
      sum += *pSrc++;
  
      /* Decrement the loop counter */
      blkCnt--;
    }
  
    /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) / blockSize  */
    /* Store the result to the destination */
    *pResult = (q15_t) (sum / (q31_t)blockSize);
  }
  
  /**    
   * @} end of mean group    
   */
  