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# arm_rms_f32.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_rms_f32.c
    00009 *
    00010 * Description:  Root mean square value of an array of F32 type
    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
    00062 void arm_rms_f32(
    00063   float32_t * pSrc,
    00064   uint32_t blockSize,
    00065   float32_t * pResult)
    00066 {
    00067   float32_t sum = 0.0f;                          /* Accumulator */
    00068   float32_t in;                                  /* Tempoprary variable to store input value */
    00069   uint32_t blkCnt;                               /* loop counter */
    00070
    00071   /* loop Unrolling */
    00072   blkCnt = blockSize >> 2u;
    00073
    00074   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
    00075    ** a second loop below computes the remaining 1 to 3 samples. */
    00076   while(blkCnt > 0u)
    00077   {
    00078     /* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */
    00079     /* Compute sum of the squares and then store the result in a temporary variable, sum  */
    00080     in = *pSrc++;
    00081     sum += in * in;
    00082     in = *pSrc++;
    00083     sum += in * in;
    00084     in = *pSrc++;
    00085     sum += in * in;
    00086     in = *pSrc++;
    00087     sum += in * in;
    00088
    00089     /* Decrement the loop counter */
    00090     blkCnt--;
    00091   }
    00092
    00093   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
    00094    ** No loop unrolling is used. */
    00095   blkCnt = blockSize % 0x4u;
    00096
    00097   while(blkCnt > 0u)
    00098   {
    00099     /* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */
    00100     /* Compute sum of the squares and then store the results in a temporary variable, sum  */
    00101     in = *pSrc++;
    00102     sum += in * in;
    00103
    00104     /* Decrement the loop counter */
    00105     blkCnt--;
    00106   }
    00107
    00108   /* Compute Rms and store the result in the destination */
    00109   arm_sqrt_f32(sum / (float32_t) blockSize, pResult);
    00110 }
    00111

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