arm_max_q15.c

00001 /* ----------------------------------------------------------------------    
00002 * Copyright (C) 2010-2014 ARM Limited. All rights reserved.    
00003 *    
00004 * $Date:        19. March 2015
00005 * $Revision:    V.1.4.5  
00006 *    
00007 * Project:      CMSIS DSP Library    
00008 * Title:        arm_max_q15.c    
00009 *    
00010 * Description:  Maximum value of a Q15 vector.    
00011 *    
00012 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
00013 *  
00014 * Redistribution and use in source and binary forms, with or without 
00015 * modification, are permitted provided that the following conditions
00016 * are met:
00017 *   - Redistributions of source code must retain the above copyright
00018 *     notice, this list of conditions and the following disclaimer.
00019 *   - Redistributions in binary form must reproduce the above copyright
00020 *     notice, this list of conditions and the following disclaimer in
00021 *     the documentation and/or other materials provided with the 
00022 *     distribution.
00023 *   - Neither the name of ARM LIMITED nor the names of its contributors
00024 *     may be used to endorse or promote products derived from this
00025 *     software without specific prior written permission.
00026 *
00027 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
00028 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
00029 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
00030 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 
00031 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
00032 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
00033 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
00034 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
00035 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
00036 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
00037 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
00038 * POSSIBILITY OF SUCH DAMAGE.    
00039 * ---------------------------------------------------------------------------- */
00040 
00041 #include "arm_math.h"
00042 
00043 /**    
00044  * @ingroup groupStats    
00045  */
00046 
00047 /**    
00048  * @addtogroup Max    
00049  * @{    
00050  */
00051 
00052 
00053 /**    
00054  * @brief Maximum value of a Q15 vector.    
00055  * @param[in]       *pSrc points to the input vector    
00056  * @param[in]       blockSize length of the input vector    
00057  * @param[out]      *pResult maximum value returned here    
00058  * @param[out]      *pIndex index of maximum value returned here    
00059  * @return none.    
00060  */
00061 
00062 void arm_max_q15(
00063   q15_t * pSrc,
00064   uint32_t blockSize,
00065   q15_t * pResult,
00066   uint32_t * pIndex)
00067 {
00068 #ifndef ARM_MATH_CM0_FAMILY
00069 
00070   /* Run the below code for Cortex-M4 and Cortex-M3 */
00071   q15_t maxVal1, maxVal2, out;                   /* Temporary variables to store the output value. */
00072   uint32_t blkCnt, outIndex, count;              /* loop counter */
00073 
00074   /* Initialise the count value. */
00075   count = 0u;
00076   /* Initialise the index value to zero. */
00077   outIndex = 0u;
00078   /* Load first input value that act as reference value for comparision */
00079   out = *pSrc++;
00080 
00081   /* Loop unrolling */
00082   blkCnt = (blockSize - 1u) >> 2u;
00083 
00084   /* Run the below code for Cortex-M4 and Cortex-M3 */
00085   while(blkCnt > 0u)
00086   {
00087     /* Initialize maxVal to the next consecutive values one by one */
00088     maxVal1 = *pSrc++;
00089 
00090     maxVal2 = *pSrc++;
00091 
00092     /* compare for the maximum value */
00093     if(out < maxVal1)
00094     {
00095       /* Update the maximum value and its index */
00096       out = maxVal1;
00097       outIndex = count + 1u;
00098     }
00099 
00100     maxVal1 = *pSrc++;
00101 
00102     /* compare for the maximum value */
00103     if(out < maxVal2)
00104     {
00105       /* Update the maximum value and its index */
00106       out = maxVal2;
00107       outIndex = count + 2u;
00108     }
00109 
00110     maxVal2 = *pSrc++;
00111 
00112     /* compare for the maximum value */
00113     if(out < maxVal1)
00114     {
00115       /* Update the maximum value and its index */
00116       out = maxVal1;
00117       outIndex = count + 3u;
00118     }
00119 
00120     /* compare for the maximum value */
00121     if(out < maxVal2)
00122     {
00123       /* Update the maximum value and its index */
00124       out = maxVal2;
00125       outIndex = count + 4u;
00126     }
00127 
00128     count += 4u;
00129 
00130     /* Decrement the loop counter */
00131     blkCnt--;
00132   }
00133 
00134   /* if (blockSize - 1u) is not multiple of 4 */
00135   blkCnt = (blockSize - 1u) % 4u;
00136 
00137 #else
00138 
00139   /* Run the below code for Cortex-M0 */
00140   q15_t maxVal1, out;                            /* Temporary variables to store the output value. */
00141   uint32_t blkCnt, outIndex;                     /* loop counter */
00142 
00143   blkCnt = (blockSize - 1u);
00144 
00145   /* Initialise the index value to zero. */
00146   outIndex = 0u;
00147   /* Load first input value that act as reference value for comparision */
00148   out = *pSrc++;
00149 
00150 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
00151 
00152   while(blkCnt > 0u)
00153   {
00154     /* Initialize maxVal to the next consecutive values one by one */
00155     maxVal1 = *pSrc++;
00156 
00157     /* compare for the maximum value */
00158     if(out < maxVal1)
00159     {
00160       /* Update the maximum value and it's index */
00161       out = maxVal1;
00162       outIndex = blockSize - blkCnt;
00163     }
00164     /* Decrement the loop counter */
00165     blkCnt--;
00166 
00167   }
00168 
00169   /* Store the maximum value and its index into destination pointers */
00170   *pResult = out;
00171   *pIndex = outIndex;
00172 }
00173 
00174 /**    
00175  * @} end of Max group    
00176  */