lib/main/CMSIS/DSP/Source/StatisticsFunctions/arm_max_q15.c

   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  */