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# arm_rms_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_rms_q15.c
    00009 *
    00010 * Description:  Root Mean Square of the elements 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
    00059 void arm_rms_q15(
    00060   q15_t * pSrc,
    00061   uint32_t blockSize,
    00062   q15_t * pResult)
    00063 {
    00064   q63_t sum = 0;                                 /* accumulator */
    00065
    00066 #ifndef ARM_MATH_CM0
    00067
    00068   /* Run the below code for Cortex-M4 and Cortex-M3 */
    00069
    00070   q31_t in;                                      /* temporary variable to store the input value */
    00071   q15_t in1;                                     /* temporary variable to store the input value */
    00072   uint32_t blkCnt;                               /* loop counter */
    00073
    00074   /* loop Unrolling */
    00075   blkCnt = blockSize >> 2u;
    00076
    00077   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
    00078    ** a second loop below computes the remaining 1 to 3 samples. */
    00079   while(blkCnt > 0u)
    00080   {
    00081     /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
    00082     /* Compute sum of the squares and then store the results in a temporary variable, sum */
    00083     in = *__SIMD32(pSrc)++;
    00084     sum = __SMLALD(in, in, sum);
    00085     in = *__SIMD32(pSrc)++;
    00086     sum = __SMLALD(in, in, sum);
    00087
    00088     /* Decrement the loop counter */
    00089     blkCnt--;
    00090   }
    00091
    00092   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
    00093    ** No loop unrolling is used. */
    00094   blkCnt = blockSize % 0x4u;
    00095
    00096   while(blkCnt > 0u)
    00097   {
    00098     /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
    00099     /* Compute sum of the squares and then store the results in a temporary variable, sum */
    00100     in1 = *pSrc++;
    00101     sum = __SMLALD(in1, in1, sum);
    00102
    00103     /* Decrement the loop counter */
    00104     blkCnt--;
    00105   }
    00106
    00107   /* Truncating and saturating the accumulator to 1.15 format */
    00108   sum = __SSAT((q31_t) (sum >> 15), 16);
    00109
    00110   in1 = (q15_t) (sum / blockSize);
    00111
    00112   /* Store the result in the destination */
    00113   arm_sqrt_q15(in1, pResult);
    00114
    00115 #else
    00116
    00117   /* Run the below code for Cortex-M0 */
    00118
    00119   q15_t in;                                      /* temporary variable to store the input value */
    00120   uint32_t blkCnt;                               /* loop counter */
    00121
    00122   /* Loop over blockSize number of values */
    00123   blkCnt = blockSize;
    00124
    00125   while(blkCnt > 0u)
    00126   {
    00127     /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
    00128     /* Compute sum of the squares and then store the results in a temporary variable, sum */
    00129     in = *pSrc++;
    00130     sum += ((q31_t) in * in);
    00131
    00132     /* Decrement the loop counter */
    00133     blkCnt--;
    00134   }
    00135
    00136   /* Truncating and saturating the accumulator to 1.15 format */
    00137   sum = __SSAT((q31_t) (sum >> 15), 16);
    00138
    00139   in = (q15_t) (sum / blockSize);
    00140
    00141   /* Store the result in the destination */
    00142   arm_sqrt_q15(in, pResult);
    00143
    00144 #endif /* #ifndef ARM_MATH_CM0 */
    00145
    00146 }
    00147

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