hardware/arduino/sam/system/CMSIS/CMSIS/DSP_Lib/Source/StatisticsFunctions/arm_max_q7.c

/* ----------------------------------------------------------------------   
* Copyright (C) 2010 ARM Limited. All rights reserved.   
*   
* $Date:        15. July 2011  
* $Revision: 	V1.0.10  
*   
* Project: 	    CMSIS DSP Library   
* Title:		arm_max_q7.c   
*   
* Description:	Maximum value of a Q7 vector.   
*   
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*  
* Version 1.0.10 2011/7/15 
*    Big Endian support added and Merged M0 and M3/M4 Source code.  
*   
* Version 1.0.3 2010/11/29  
*    Re-organized the CMSIS folders and updated documentation.   
*    
* Version 1.0.2 2010/11/11   
*    Documentation updated.    
*   
* Version 1.0.1 2010/10/05    
*    Production release and review comments incorporated.   
*   
* Version 1.0.0 2010/09/20    
*    Production release and review comments incorporated.   
* ---------------------------------------------------------------------------- */

#include "arm_math.h"

/**   
 * @ingroup groupStats   
 */

/**   
 * @addtogroup Max   
 * @{   
 */


/**   
 * @brief Maximum value of a Q7 vector.   
 * @param[in]       *pSrc points to the input vector   
 * @param[in]       blockSize length of the input vector   
 * @param[out]      *pResult maximum value returned here   
 * @param[out]      *pIndex index of maximum value returned here   
  * @return none.   
 */

void arm_max_q7(
  q7_t * pSrc,
  uint32_t blockSize,
  q7_t * pResult,
  uint32_t * pIndex)
{

#ifndef ARM_MATH_CM0

  /* Run the below code for Cortex-M4 and Cortex-M3 */

  q7_t res, maxVal, x0, x1, maxVal2, maxVal1;    /* Temporary variables to store the output value. */
  uint32_t blkCnt, index1, index2, index3, indx, indxMod;       /* loop counter */

  /* Initialise the index value to zero. */
  indx = 0u;

  /* Load first input value that act as reference value for comparision */
  res = *pSrc++;

  /* Loop unrolling */
  blkCnt = (blockSize - 1u) >> 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)
  {
    indxMod = blockSize - (blkCnt * 4u);

    /* Load two input values for comparision */
    x0 = *pSrc++;
    x1 = *pSrc++;

    if(x0 < x1)
    {
      /* Update the maximum value and its index */
      maxVal1 = x1;
      index1 = indxMod + 1u;
    }
    else
    {
      /* Update the maximum value and its index */
      maxVal1 = x0;
      index1 = indxMod;
    }

    /* Load two input values for comparision */
    x0 = *pSrc++;
    x1 = *pSrc++;

    if(x0 < x1)
    {
      /* Update the maximum value and its index */
      maxVal2 = x1;
      index2 = indxMod + 3u;
    }
    else
    {
      /* Update the maximum value and its index */
      maxVal2 = x0;
      index2 = indxMod + 2u;
    }

    if(maxVal1 < maxVal2)
    {
      /* Update the maximum value and its index */
      maxVal = maxVal2;
      index3 = index2;
    }
    else
    {
      /* Update the maximum value and its index */
      maxVal = maxVal1;
      index3 = index1;
    }

    if(res < maxVal)
    {
      /* Update the maximum value and its index */
      res = maxVal;
      indx = index3;
    }

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

  }

  /* If the blockSize - 1 is not a multiple of 4, compute any remaining output samples here.  
   ** No loop unrolling is used. */
  blkCnt = (blockSize - 1u) % 0x04u;

  while(blkCnt > 0u)
  {
    /* Initialize maxVal to the next consecutive values one by one */
    maxVal = *pSrc++;

    /* compare for the maximum value */
    if(res < maxVal)
    {
      /* Update the maximum value and its index */
      res = maxVal;
      indx = blockSize - blkCnt;
    }

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

  /* Store the maximum value and its index into destination pointers */
  *pResult = res;
  *pIndex = indx;

#else

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

  q7_t maxVal, out;                              /* Temporary variables to store the output value. */
  uint32_t blkCnt, outIndex;                     /* loop counter */

  /* Initialise the index value to zero. */
  outIndex = 0u;
  /* Load first input value that act as reference value for comparision */
  out = *pSrc++;

  /* Loop over blockSize - 1 number of values */
  blkCnt = (blockSize - 1u);

  while(blkCnt > 0u)
  {
    /* Initialize maxVal to the next consecutive values one by one */
    maxVal = *pSrc++;

    /* compare for the maximum value */
    if(out < maxVal)
    {
      /* Update the maximum value and its index */
      out = maxVal;
      outIndex = blockSize - blkCnt;
    }
    /* Decrement the loop counter */
    blkCnt--;

  }

  /* Store the maximum value and its index into destination pointers */
  *pResult = out;
  *pIndex = outIndex;

#endif /* #ifndef ARM_MATH_CM0 */

}

/**   
 * @} end of Max group   
 */