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2 mjames 1 
/* ----------------------------------------------------------------------
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 * Project:      CMSIS DSP Library
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 * Title:        arm_max_q31.c
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 * Description:  Maximum value of a Q31 vector
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 *
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 * $Date:        27. January 2017
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 * $Revision:    V.1.5.1
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 *
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 * Target Processor: Cortex-M cores
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 * -------------------------------------------------------------------- */
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/*
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 * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
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 *
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 * SPDX-License-Identifier: Apache-2.0
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 *
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 * Licensed under the Apache License, Version 2.0 (the License); you may
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 * not use this file except in compliance with the License.
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 * You may obtain a copy of the License at
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 *
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 * www.apache.org/licenses/LICENSE-2.0
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 *
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 * Unless required by applicable law or agreed to in writing, software
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 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
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 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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 * See the License for the specific language governing permissions and
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 * limitations under the License.
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 */
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#include "arm_math.h"
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/**
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 * @ingroup groupStats
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 */
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/**
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 * @addtogroup Max
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 * @{
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 */
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/**
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 * @brief Maximum value of a Q31 vector.
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 * @param[in]       *pSrc points to the input vector
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 * @param[in]       blockSize length of the input vector
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 * @param[out]      *pResult maximum value returned here
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 * @param[out]      *pIndex index of maximum value returned here
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 * @return none.
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 */
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void arm_max_q31(
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  q31_t * pSrc,
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  uint32_t blockSize,
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  q31_t * pResult,
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  uint32_t * pIndex)
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{
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#if defined (ARM_MATH_DSP)
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  /* Run the below code for Cortex-M4 and Cortex-M3 */
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  q31_t maxVal1, maxVal2, out;                   /* Temporary variables to store the output value. */
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  uint32_t blkCnt, outIndex, count;              /* loop counter */
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  /* Initialise the count value. */
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  count = 0U;
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  /* Initialise the index value to zero. */
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  outIndex = 0U;
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  /* Load first input value that act as reference value for comparision */
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  out = *pSrc++;
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  /* Loop unrolling */
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  blkCnt = (blockSize - 1U) >> 2U;
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  while (blkCnt > 0U)
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  {
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    /* Initialize maxVal to the next consecutive values one by one */
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    maxVal1 = *pSrc++;
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    maxVal2 = *pSrc++;
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    /* compare for the maximum value */
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    if (out < maxVal1)
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    {
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      /* Update the maximum value and its index */
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      out = maxVal1;
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      outIndex = count + 1U;
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    }
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    /* compare for the maximum value */
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    if (out < maxVal2)
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    {
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      /* Update the maximum value and its index */
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      out = maxVal2;
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      outIndex = count + 2U;
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    }
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    /* Initialize maxVal to the next consecutive values one by one */
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    maxVal1 = *pSrc++;
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    maxVal2 = *pSrc++;
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    /* compare for the maximum value */
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    if (out < maxVal1)
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    {
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      /* Update the maximum value and its index */
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      out = maxVal1;
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      outIndex = count + 3U;
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    }
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    /* compare for the maximum value */
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    if (out < maxVal2)
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    {
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      /* Update the maximum value and its index */
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      out = maxVal2;
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      outIndex = count + 4U;
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    }
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    count += 4U;
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    /* Decrement the loop counter */
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    blkCnt--;
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  }
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  /* if (blockSize - 1U) is not multiple of 4 */
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  blkCnt = (blockSize - 1U) % 4U;
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#else
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  /* Run the below code for Cortex-M0 */
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  q31_t maxVal1, out;                            /* Temporary variables to store the output value. */
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  uint32_t blkCnt, outIndex;                     /* loop counter */
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  /* Initialise the index value to zero. */
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  outIndex = 0U;
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  /* Load first input value that act as reference value for comparision */
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  out = *pSrc++;
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  blkCnt = (blockSize - 1U);
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#endif /* #if defined (ARM_MATH_DSP) */
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  while (blkCnt > 0U)
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  {
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    /* Initialize maxVal to the next consecutive values one by one */
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    maxVal1 = *pSrc++;
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    /* compare for the maximum value */
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    if (out < maxVal1)
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    {
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      /* Update the maximum value and it's index */
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      out = maxVal1;
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      outIndex = blockSize - blkCnt;
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    }
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    /* Decrement the loop counter */
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    blkCnt--;
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  }
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  /* Store the maximum value and it's index into destination pointers */
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  *pResult = out;
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  *pIndex = outIndex;
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}
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/**
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 * @} end of Max group
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 */