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  1. /* ----------------------------------------------------------------------
  2.  * Project:      CMSIS DSP Library
  3.  * Title:        arm_max_q15.c
  4.  * Description:  Maximum value of a Q15 vector
  5.  *
  6.  * $Date:        27. January 2017
  7.  * $Revision:    V.1.5.1
  8.  *
  9.  * Target Processor: Cortex-M cores
  10.  * -------------------------------------------------------------------- */
  11. /*
  12.  * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
  13.  *
  14.  * SPDX-License-Identifier: Apache-2.0
  15.  *
  16.  * Licensed under the Apache License, Version 2.0 (the License); you may
  17.  * not use this file except in compliance with the License.
  18.  * You may obtain a copy of the License at
  19.  *
  20.  * www.apache.org/licenses/LICENSE-2.0
  21.  *
  22.  * Unless required by applicable law or agreed to in writing, software
  23.  * distributed under the License is distributed on an AS IS BASIS, WITHOUT
  24.  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  25.  * See the License for the specific language governing permissions and
  26.  * limitations under the License.
  27.  */
  28.  
  29. #include "arm_math.h"
  30.  
  31. /**
  32.  * @ingroup groupStats
  33.  */
  34.  
  35. /**
  36.  * @addtogroup Max
  37.  * @{
  38.  */
  39.  
  40.  
  41. /**
  42.  * @brief Maximum value of a Q15 vector.
  43.  * @param[in]       *pSrc points to the input vector
  44.  * @param[in]       blockSize length of the input vector
  45.  * @param[out]      *pResult maximum value returned here
  46.  * @param[out]      *pIndex index of maximum value returned here
  47.  * @return none.
  48.  */
  49.  
  50. void arm_max_q15(
  51.   q15_t * pSrc,
  52.   uint32_t blockSize,
  53.   q15_t * pResult,
  54.   uint32_t * pIndex)
  55. {
  56. #if defined (ARM_MATH_DSP)
  57.   /* Run the below code for Cortex-M4 and Cortex-M3 */
  58.  
  59.   q15_t maxVal1, maxVal2, out;                   /* Temporary variables to store the output value. */
  60.   uint32_t blkCnt, outIndex, count;              /* loop counter */
  61.  
  62.   /* Initialise the count value. */
  63.   count = 0U;
  64.   /* Initialise the index value to zero. */
  65.   outIndex = 0U;
  66.   /* Load first input value that act as reference value for comparision */
  67.   out = *pSrc++;
  68.  
  69.   /* Loop unrolling */
  70.   blkCnt = (blockSize - 1U) >> 2U;
  71.  
  72.   while (blkCnt > 0U)
  73.   {
  74.     /* Initialize maxVal to the next consecutive values one by one */
  75.     maxVal1 = *pSrc++;
  76.     maxVal2 = *pSrc++;
  77.  
  78.     /* compare for the maximum value */
  79.     if (out < maxVal1)
  80.     {
  81.       /* Update the maximum value and its index */
  82.       out = maxVal1;
  83.       outIndex = count + 1U;
  84.     }
  85.  
  86.     /* compare for the maximum value */
  87.     if (out < maxVal2)
  88.     {
  89.       /* Update the maximum value and its index */
  90.       out = maxVal2;
  91.       outIndex = count + 2U;
  92.     }
  93.  
  94.     /* Initialize maxVal to the next consecutive values one by one */
  95.     maxVal1 = *pSrc++;
  96.     maxVal2 = *pSrc++;
  97.  
  98.     /* compare for the maximum value */
  99.     if (out < maxVal1)
  100.     {
  101.       /* Update the maximum value and its index */
  102.       out = maxVal1;
  103.       outIndex = count + 3U;
  104.     }
  105.  
  106.     /* compare for the maximum value */
  107.     if (out < maxVal2)
  108.     {
  109.       /* Update the maximum value and its index */
  110.       out = maxVal2;
  111.       outIndex = count + 4U;
  112.     }
  113.  
  114.     count += 4U;
  115.  
  116.     /* Decrement the loop counter */
  117.     blkCnt--;
  118.   }
  119.  
  120.   /* if (blockSize - 1U) is not multiple of 4 */
  121.   blkCnt = (blockSize - 1U) % 4U;
  122.  
  123. #else
  124.   /* Run the below code for Cortex-M0 */
  125.  
  126.   q15_t maxVal1, out;                            /* Temporary variables to store the output value. */
  127.   uint32_t blkCnt, outIndex;                     /* loop counter */
  128.  
  129.   /* Initialise the index value to zero. */
  130.   outIndex = 0U;
  131.   /* Load first input value that act as reference value for comparision */
  132.   out = *pSrc++;
  133.  
  134.   blkCnt = (blockSize - 1U);
  135.  
  136. #endif /* #if defined (ARM_MATH_DSP) */
  137.  
  138.   while (blkCnt > 0U)
  139.   {
  140.     /* Initialize maxVal to the next consecutive values one by one */
  141.     maxVal1 = *pSrc++;
  142.  
  143.     /* compare for the maximum value */
  144.     if (out < maxVal1)
  145.     {
  146.       /* Update the maximum value and it's index */
  147.       out = maxVal1;
  148.       outIndex = blockSize - blkCnt;
  149.     }
  150.  
  151.     /* Decrement the loop counter */
  152.     blkCnt--;
  153.   }
  154.  
  155.   /* Store the maximum value and it's index into destination pointers */
  156.   *pResult = out;
  157.   *pIndex = outIndex;
  158. }
  159.  
  160. /**
  161.  * @} end of Max group
  162.  */
  163.