arm_cmplx_dot_prod_q15.c

/* ----------------------------------------------------------------------    
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.    
*    
* $Date:        19. March 2015
* $Revision: 	V.1.4.5
*    
* Project: 	    CMSIS DSP Library    
* Title:		arm_cmplx_dot_prod_q15.c    
*    
* Description:	Processing function for the Q15 Complex Dot product    
*    
* 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,
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* -------------------------------------------------------------------- */

#include "arm_math.h"

/**    
 * @ingroup groupCmplxMath    
 */

/**    
 * @addtogroup cmplx_dot_prod    
 * @{    
 */

/**    
 * @brief  Q15 complex dot product    
 * @param  *pSrcA points to the first input vector    
 * @param  *pSrcB points to the second input vector    
 * @param  numSamples number of complex samples in each vector    
 * @param  *realResult real part of the result returned here    
 * @param  *imagResult imaginary part of the result returned here    
 * @return none.    
 *    
 * <b>Scaling and Overflow Behavior:</b>    
 * \par    
 * The function is implemented using an internal 64-bit accumulator.    
 * The intermediate 1.15 by 1.15 multiplications are performed with full precision and yield a 2.30 result.    
 * These are accumulated in a 64-bit accumulator with 34.30 precision.    
 * As a final step, the accumulators are converted to 8.24 format.    
 * The return results <code>realResult</code> and <code>imagResult</code> are in 8.24 format.    
 */

void arm_cmplx_dot_prod_q15(
  q15_t * pSrcA,
  q15_t * pSrcB,
  uint32_t numSamples,
  q31_t * realResult,
  q31_t * imagResult)
{
  q63_t real_sum = 0, imag_sum = 0;              /* Temporary result storage */
  q15_t a0,b0,c0,d0;

#ifndef ARM_MATH_CM0_FAMILY

  /* Run the below code for Cortex-M4 and Cortex-M3 */
  uint32_t blkCnt;                               /* loop counter */


  /*loop Unrolling */
  blkCnt = numSamples >> 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)
  {
      a0 = *pSrcA++;
      b0 = *pSrcA++;
      c0 = *pSrcB++;
      d0 = *pSrcB++;  
  
      real_sum += (q31_t)a0 * c0;
      imag_sum += (q31_t)a0 * d0;
      real_sum -= (q31_t)b0 * d0;
      imag_sum += (q31_t)b0 * c0;
      
      a0 = *pSrcA++;
      b0 = *pSrcA++;
      c0 = *pSrcB++;
      d0 = *pSrcB++;  
  
      real_sum += (q31_t)a0 * c0;
      imag_sum += (q31_t)a0 * d0;
      real_sum -= (q31_t)b0 * d0;
      imag_sum += (q31_t)b0 * c0;
      
      a0 = *pSrcA++;
      b0 = *pSrcA++;
      c0 = *pSrcB++;
      d0 = *pSrcB++;  
  
      real_sum += (q31_t)a0 * c0;
      imag_sum += (q31_t)a0 * d0;
      real_sum -= (q31_t)b0 * d0;
      imag_sum += (q31_t)b0 * c0;
      
      a0 = *pSrcA++;
      b0 = *pSrcA++;
      c0 = *pSrcB++;
      d0 = *pSrcB++;  
  
      real_sum += (q31_t)a0 * c0;
      imag_sum += (q31_t)a0 * d0;
      real_sum -= (q31_t)b0 * d0;
      imag_sum += (q31_t)b0 * c0;

      /* Decrement the loop counter */
      blkCnt--;
  }

  /* If the numSamples is not a multiple of 4, compute any remaining output samples here.    
   ** No loop unrolling is used. */
  blkCnt = numSamples % 0x4u;

  while(blkCnt > 0u)
  {
      a0 = *pSrcA++;
      b0 = *pSrcA++;
      c0 = *pSrcB++;
      d0 = *pSrcB++;  
  
      real_sum += (q31_t)a0 * c0;
      imag_sum += (q31_t)a0 * d0;
      real_sum -= (q31_t)b0 * d0;
      imag_sum += (q31_t)b0 * c0;

      /* Decrement the loop counter */
      blkCnt--;
  }

#else

  /* Run the below code for Cortex-M0 */

  while(numSamples > 0u)
  {
      a0 = *pSrcA++;
      b0 = *pSrcA++;
      c0 = *pSrcB++;
      d0 = *pSrcB++;  
  
      real_sum += a0 * c0;
      imag_sum += a0 * d0;
      real_sum -= b0 * d0;
      imag_sum += b0 * c0;


      /* Decrement the loop counter */
      numSamples--;
  }

#endif /* #ifndef ARM_MATH_CM0_FAMILY */

  /* Store the real and imaginary results in 8.24 format  */
  /* Convert real data in 34.30 to 8.24 by 6 right shifts */
  *realResult = (q31_t) (real_sum >> 6);
  /* Convert imaginary data in 34.30 to 8.24 by 6 right shifts */
  *imagResult = (q31_t) (imag_sum >> 6);
}

/**    
 * @} end of cmplx_dot_prod group    
 */