tmk_core/tool/mbed/mbed-sdk/libraries/dsp/cmsis_dsp/StatisticsFunctions/arm_rms_q15.c

   1 /* ----------------------------------------------------------------------
   2 * Copyright (C) 2010-2013 ARM Limited. All rights reserved.
   3 *
   4 * $Date:        17. January 2013
   5 * $Revision:    V1.4.1
   6 *
   7 * Project:          CMSIS DSP Library
   8 * Title:                arm_rms_q15.c
   9 *
  10 * Description:  Root Mean Square of the elements of a Q15 vector.
  11 *
  12 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
  13 *
  14 * Redistribution and use in source and binary forms, with or without
  15 * modification, are permitted provided that the following conditions
  16 * are met:
  17 *   - Redistributions of source code must retain the above copyright
  18 *     notice, this list of conditions and the following disclaimer.
  19 *   - Redistributions in binary form must reproduce the above copyright
  20 *     notice, this list of conditions and the following disclaimer in
  21 *     the documentation and/or other materials provided with the
  22 *     distribution.
  23 *   - Neither the name of ARM LIMITED nor the names of its contributors
  24 *     may be used to endorse or promote products derived from this
  25 *     software without specific prior written permission.
  26 *
  27 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  28 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  29 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  30 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  31 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  32 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  33 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  34 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  35 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  37 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  38 * POSSIBILITY OF SUCH DAMAGE.
  39 * ---------------------------------------------------------------------------- */
  40
  41 #include "arm_math.h"
  42
  43 /**
  44  * @addtogroup RMS
  45  * @{
  46  */
  47
  48 /**
  49  * @brief Root Mean Square of the elements of a Q15 vector.
  50  * @param[in]       *pSrc points to the input vector
  51  * @param[in]       blockSize length of the input vector
  52  * @param[out]      *pResult rms value returned here
  53  * @return none.
  54  *
  55  * @details
  56  * <b>Scaling and Overflow Behavior:</b>
  57  *
  58  * \par
  59  * The function is implemented using a 64-bit internal accumulator.
  60  * The input is represented in 1.15 format.
  61  * Intermediate multiplication yields a 2.30 format, and this
  62  * result is added without saturation to a 64-bit accumulator in 34.30 format.
  63  * With 33 guard bits in the accumulator, there is no risk of overflow, and the
  64  * full precision of the intermediate multiplication is preserved.
  65  * Finally, the 34.30 result is truncated to 34.15 format by discarding the lower
  66  * 15 bits, and then saturated to yield a result in 1.15 format.
  67  *
  68  */
  69
  70 void arm_rms_q15(
  71   q15_t * pSrc,
  72   uint32_t blockSize,
  73   q15_t * pResult)
  74 {
  75   q63_t sum = 0;                                 /* accumulator */
  76
  77 #ifndef ARM_MATH_CM0_FAMILY
  78
  79   /* Run the below code for Cortex-M4 and Cortex-M3 */
  80
  81   q31_t in;                                      /* temporary variable to store the input value */
  82   q15_t in1;                                     /* temporary variable to store the input value */
  83   uint32_t blkCnt;                               /* loop counter */
  84
  85   /* loop Unrolling */
  86   blkCnt = blockSize >> 2u;
  87
  88   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
  89    ** a second loop below computes the remaining 1 to 3 samples. */
  90   while(blkCnt > 0u)
  91   {
  92     /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
  93     /* Compute sum of the squares and then store the results in a temporary variable, sum */
  94     in = *__SIMD32(pSrc)++;
  95     sum = __SMLALD(in, in, sum);
  96     in = *__SIMD32(pSrc)++;
  97     sum = __SMLALD(in, in, sum);
  98
  99     /* Decrement the loop counter */
 100     blkCnt--;
 101   }
 102
 103   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
 104    ** No loop unrolling is used. */
 105   blkCnt = blockSize % 0x4u;
 106
 107   while(blkCnt > 0u)
 108   {
 109     /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
 110     /* Compute sum of the squares and then store the results in a temporary variable, sum */
 111     in1 = *pSrc++;
 112     sum = __SMLALD(in1, in1, sum);
 113
 114     /* Decrement the loop counter */
 115     blkCnt--;
 116   }
 117
 118   /* Truncating and saturating the accumulator to 1.15 format */
 119   in = (q31_t)(sum >> 15);
 120
 121   in1 = __SSAT(in / blockSize, 16);
 122
 123   /* Store the result in the destination */
 124   arm_sqrt_q15(in1, pResult);
 125
 126 #else
 127
 128   /* Run the below code for Cortex-M0 */
 129
 130   q15_t in;                                      /* temporary variable to store the input value */
 131   q31_t tmp;                                     /* temporary variable to store the input value */
 132   uint32_t blkCnt;                               /* loop counter */
 133
 134   /* Loop over blockSize number of values */
 135   blkCnt = blockSize;
 136
 137   while(blkCnt > 0u)
 138   {
 139     /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
 140     /* Compute sum of the squares and then store the results in a temporary variable, sum */
 141     in = *pSrc++;
 142     sum += ((q31_t) in * in);
 143
 144     /* Decrement the loop counter */
 145     blkCnt--;
 146   }
 147
 148   /* Truncating and saturating the accumulator to 1.15 format */
 149   tmp = (q31_t)(sum >> 15);
 150
 151   in = __SSAT(tmp / blockSize, 16);
 152
 153   /* Store the result in the destination */
 154   arm_sqrt_q15(in, pResult);
 155
 156 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
 157
 158 }
 159
 160 /**
 161  * @} end of RMS group
 162  */