arm_max_q7.c

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  
00029 /**  
00030  * @ingroup groupStats  
00031  */ 
00032  
00033 /**  
00034  * @addtogroup Max  
00035  * @{  
00036  */ 
00037  
00038  
00039 /**  
00040  * @brief Maximum value of a Q7 vector.  
00041  * @param[in]       *pSrc points to the input vector  
00042  * @param[in]       blockSize length of the input vector  
00043  * @param[out]      *pResult maximum value returned here  
00044  * @param[out]      *pIndex index of maximum value returned here  
00045   * @return none.  
00046  */ 
00047  
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  
00153 /**  
00154  * @} end of Max group  
00155  */