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# arm_rms_q31.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_rms_q31.c
    00009 *
    00010 * Description:  Root Mean Square of the elements of a Q31 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
    00062 void arm_rms_q31(
    00063   q31_t * pSrc,
    00064   uint32_t blockSize,
    00065   q31_t * pResult)
    00066 {
    00067   q63_t sum = 0;                                 /* accumulator */
    00068   q31_t in;                                      /* Temporary variable to store the input */
    00069   uint32_t blkCnt;                               /* loop counter */
    00070
    00071 #ifndef ARM_MATH_CM0
    00072
    00073   /* Run the below code for Cortex-M4 and Cortex-M3 */
    00074
    00075   q31_t *pIn1 = pSrc;                            /* SrcA pointer */
    00076
    00077   /*loop Unrolling */
    00078   blkCnt = blockSize >> 2u;
    00079
    00080   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
    00081    ** a second loop below computes the remaining 1 to 3 samples. */
    00082   while(blkCnt > 0u)
    00083   {
    00084     /* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */
    00085     /* Compute sum of the squares and then store the result in a temporary variable, sum */
    00086     in = *pIn1++;
    00087     sum += (q63_t) in *in;
    00088     in = *pIn1++;
    00089     sum += (q63_t) in *in;
    00090     in = *pIn1++;
    00091     sum += (q63_t) in *in;
    00092     in = *pIn1++;
    00093     sum += (q63_t) in *in;
    00094
    00095     /* Decrement the loop counter */
    00096     blkCnt--;
    00097   }
    00098
    00099   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
    00100    ** No loop unrolling is used. */
    00101   blkCnt = blockSize % 0x4u;
    00102
    00103   while(blkCnt > 0u)
    00104   {
    00105     /* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */
    00106     /* Compute sum of the squares and then store the results in a temporary variable, sum */
    00107     in = *pIn1++;
    00108     sum += (q63_t) in *in;
    00109
    00110     /* Decrement the loop counter */
    00111     blkCnt--;
    00112   }
    00113
    00114 #else
    00115
    00116   /* Run the below code for Cortex-M0 */
    00117
    00118   /* Loop over blockSize number of values */
    00119   blkCnt = blockSize;
    00120
    00121   while(blkCnt > 0u)
    00122   {
    00123     /* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */
    00124     /* Compute sum of the squares and then store the results in a temporary variable, sum */
    00125     in = *pSrc++;
    00126     sum += (q63_t) in *in;
    00127
    00128     /* Decrement the loop counter */
    00129     blkCnt--;
    00130   }
    00131
    00132 #endif /* #ifndef ARM_MATH_CM0 */
    00133
    00134   /* Convert data in 2.62 to 1.31 by 31 right shifts */
    00135   sum = sum >> 31;
    00136
    00137   /* Compute Rms and store the result in the destination vector */
    00138   arm_sqrt_q31((q31_t) (sum / (int32_t) blockSize), pResult);
    00139 }
    00140

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