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# arm_max_q7.c

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    00001 /* ----------------------------------------------------------------------
    00002 * Copyright (C) 2010 ARM Limited. All rights reserved.
    00003 *
    00004 * $Date:        29. November 2010
    00005 * $Revision:    V1.0.3
    00006 *
    00007 * Project:      CMSIS DSP Library
    00008 * Title:        arm_max_q7.c
    00009 *
    00010 * Description:  Maximum value of a Q7 vector.
    00011 *
    00012 * Target Processor: Cortex-M4/Cortex-M3
    00013 *
    00014 * Version 1.0.3 2010/11/29
    00015 *    Re-organized the CMSIS folders and updated documentation.
    00016 *
    00017 * Version 1.0.2 2010/11/11
    00018 *    Documentation updated.
    00019 *
    00020 * Version 1.0.1 2010/10/05
    00021 *    Production release and review comments incorporated.
    00022 *
    00023 * Version 1.0.0 2010/09/20
    00024 *    Production release and review comments incorporated.
    00025 * ---------------------------------------------------------------------------- */
    00026
    00027 #include "arm_math.h"
    00028
    00048 void arm_max_q7(
    00049   q7_t * pSrc,
    00050   uint32_t blockSize,
    00051   q7_t * pResult,
    00052   uint32_t * pIndex)
    00053 {
    00054   q7_t res, maxVal, x0, x1, maxVal2, maxVal1;    /* Temporary variables to store the output value. */
    00055   uint32_t blkCnt, index1, index2, index3, indx, indxMod;       /* loop counter */
    00056
    00057   /* Initialise the index value to zero. */
    00058   indx = 0u;
    00059
    00060   /* Load first input value that act as reference value for comparision */
    00061   res = *pSrc++;
    00062
    00063   /* Loop over blockSize number of values */
    00064   blkCnt = (blockSize - 1u) >> 2u;
    00065
    00066   while(blkCnt > 0u)
    00067   {
    00068     indxMod = blockSize - (blkCnt * 4u);
    00069
    00070     /* Load two input values for comparision */
    00071     x0 = *pSrc++;
    00072     x1 = *pSrc++;
    00073
    00074     if(x0 < x1)
    00075     {
    00076       /* Update the minimum value and its index */
    00077       maxVal1 = x1;
    00078       index1 = indxMod + 1u;
    00079     }
    00080     else
    00081     {
    00082       /* Update the minimum value and its index */
    00083       maxVal1 = x0;
    00084       index1 = indxMod;
    00085     }
    00086
    00087     /* Load two input values for comparision */
    00088     x0 = *pSrc++;
    00089     x1 = *pSrc++;
    00090
    00091     if(x0 < x1)
    00092     {
    00093       /* Update the minimum value and its index */
    00094       maxVal2 = x1;
    00095       index2 = indxMod + 3u;
    00096     }
    00097     else
    00098     {
    00099       /* Update the minimum value and its index */
    00100       maxVal2 = x0;
    00101       index2 = indxMod + 2u;
    00102     }
    00103
    00104     if(maxVal1 < maxVal2)
    00105     {
    00106       /* Update the minimum value and its index */
    00107       maxVal = maxVal2;
    00108       index3 = index2;
    00109     }
    00110     else
    00111     {
    00112       /* Update the minimum value and its index */
    00113       maxVal = maxVal1;
    00114       index3 = index1;
    00115     }
    00116
    00117     if(res < maxVal)
    00118     {
    00119       /* Update the minimum value and its index */
    00120       res = maxVal;
    00121       indx = index3;
    00122     }
    00123
    00124     /* Decrement the loop counter */
    00125     blkCnt--;
    00126
    00127   }
    00128
    00129   blkCnt = (blockSize - 1u) % 0x04u;
    00130
    00131   while(blkCnt > 0u)
    00132   {
    00133     /* Initialize maxVal to the next consecutive values one by one */
    00134     maxVal = *pSrc++;
    00135
    00136     /* compare for the maximum value */
    00137     if(res < maxVal)
    00138     {
    00139       /* Update the maximum value and its index */
    00140       res = maxVal;
    00141       indx = blockSize - blkCnt;
    00142     }
    00143
    00144     /* Decrement the loop counter */
    00145     blkCnt--;
    00146   }
    00147
    00148   /* Store the maximum value and its index into destination pointers */
    00149   *pResult = res;
    00150   *pIndex = indx;
    00151 }
    00152

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