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_rms_q15.c    
  *    
  * Description:	Root Mean Square of the elements 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.  
  
   Modifications 2017  Mostafa Saleh       (Ported to RISC-V PULPino)       
  * ---------------------------------------------------------------------------- */
  
  #include <riscv_dsp/riscv_math.h>
  
  /**    
   * @addtogroup RMS    
   * @{    
   */
  
  /**    
   * @brief Root Mean Square of the elements of a Q15 vector.    
   * @param[in]       *pSrc points to the input vector    
   * @param[in]       blockSize length of the input vector    
   * @param[out]      *pResult rms value returned here    
   * @return none.    
   *    
   * @details    
   * <b>Scaling and Overflow Behavior:</b>    
   *    
   * \par    
   * The function is implemented using a 64-bit internal accumulator.    
   * The input is represented in 1.15 format.    
   * Intermediate multiplication yields a 2.30 format, and this    
   * result is added without saturation to a 64-bit accumulator in 34.30 format.    
   * With 33 guard bits in the accumulator, there is no risk of overflow, and the    
   * full precision of the intermediate multiplication is preserved.    
   * Finally, the 34.30 result is truncated to 34.15 format by discarding the lower     
   * 15 bits, and then saturated to yield a result in 1.15 format.    
   *    
   */
  
  void riscv_rms_q15(
    q15_t * pSrc,
    uint32_t blockSize,
    q15_t * pResult)
  {
    q63_t sum = 0;                                 /* accumulator */
  
    q15_t in;                                      /* temporary variable to store the input value */
    uint32_t blkCnt;                               /* loop counter */
  #if defined (USE_DSP_RISCV)
    blkCnt = blockSize>>1;
    shortV *VectInA;
  
    while(blkCnt > 0u)
    {
      /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
      VectInA = (shortV*)pSrc;
      sum += dotpv2(*VectInA, *VectInA);
      pSrc+=2;
      /* Decrement the loop counter */
      blkCnt--;
    }
    blkCnt = blockSize%0x02;
    while(blkCnt > 0u)
    {
      /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
      sum += *pSrc++;
  
      /* Decrement the loop counter */
      blkCnt--;
    }
    riscv_sqrt_q15(clip((sum / (q63_t)blockSize) >> 15,-32768,32767), pResult);
  #else
    /* Loop over blockSize number of values */
    blkCnt = blockSize;
  
    while(blkCnt > 0u)
    {
      /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
      /* Compute sum of the squares and then store the results in a temporary variable, sum */
      in = *pSrc++;
      sum += ((q31_t) in * in);
  
      /* Decrement the loop counter */
      blkCnt--;
    }
  
    /* Truncating and saturating the accumulator to 1.15 format */
    /* Store the result in the destination */
    riscv_sqrt_q15(__SSAT((sum / (q63_t)blockSize) >> 15, 16), pResult);
  #endif
  }
  
  /**    
   * @} end of RMS group    
   */
  