CMSIS DSP Software Library: arm_mean_q15.c Source File

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# arm_mean_q15.c

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    00001 /* ----------------------------------------------------------------------
    00002 * Copyright (C) 2010 ARM Limited. All rights reserved.
    00003 *
    00004 * $Date:        15. July 2011
    00005 * $Revision:    V1.0.10
    00006 *
    00007 * Project:      CMSIS DSP Library
    00008 * Title:        arm_mean_q15.c
    00009 *
    00010 * Description:  Mean value of a Q15 vector.
    00011 *
    00012 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
    00013 *
    00014 * Version 1.0.10 2011/7/15
    00015 *    Big Endian support added and Merged M0 and M3/M4 Source code.
    00016 *
    00017 * Version 1.0.3 2010/11/29
    00018 *    Re-organized the CMSIS folders and updated documentation.
    00019 *
    00020 * Version 1.0.2 2010/11/11
    00021 *    Documentation updated.
    00022 *
    00023 * Version 1.0.1 2010/10/05
    00024 *    Production release and review comments incorporated.
    00025 *
    00026 * Version 1.0.0 2010/09/20
    00027 *    Production release and review comments incorporated.
    00028 * -------------------------------------------------------------------- */
    00029
    00030 #include "arm_math.h"
    00031
    00061 void arm_mean_q15(
    00062   q15_t * pSrc,
    00063   uint32_t blockSize,
    00064   q15_t * pResult)
    00065 {
    00066   q31_t sum = 0;                                 /* Temporary result storage */
    00067   uint32_t blkCnt;                               /* loop counter */
    00068
    00069 #ifndef ARM_MATH_CM0
    00070
    00071   /* Run the below code for Cortex-M4 and Cortex-M3 */
    00072
    00073   /*loop Unrolling */
    00074   blkCnt = blockSize >> 2u;
    00075
    00076   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
    00077    ** a second loop below computes the remaining 1 to 3 samples. */
    00078   while(blkCnt > 0u)
    00079   {
    00080     /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
    00081     sum += *pSrc++;
    00082     sum += *pSrc++;
    00083     sum += *pSrc++;
    00084     sum += *pSrc++;
    00085
    00086     /* Decrement the loop counter */
    00087     blkCnt--;
    00088   }
    00089
    00090   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
    00091    ** No loop unrolling is used. */
    00092   blkCnt = blockSize % 0x4u;
    00093
    00094 #else
    00095
    00096   /* Run the below code for Cortex-M0 */
    00097
    00098   /* Loop over blockSize number of values */
    00099   blkCnt = blockSize;
    00100
    00101 #endif /* #ifndef ARM_MATH_CM0 */
    00102
    00103   while(blkCnt > 0u)
    00104   {
    00105     /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
    00106     sum += *pSrc++;
    00107
    00108     /* Decrement the loop counter */
    00109     blkCnt--;
    00110   }
    00111
    00112   /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) / blockSize  */
    00113   /* Store the result to the destination */
    00114   *pResult = (q15_t) (sum / blockSize);
    00115 }
    00116

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