Subversion Repositories DashDisplay

Rev

Rev 2 | Details | Compare with Previous | Last modification | View Log | RSS feed

Rev Author Line No. Line
2 mjames 1 
/* ----------------------------------------------------------------------    
2 
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.    
3 
*    
4 
* $Date:        19. March 2015
5 
* $Revision:    V.1.4.5  
6 
*    
7 
* Project:          CMSIS DSP Library    
8 
* Title:                arm_var_q15.c    
9 
*    
10 
* Description:  Variance of an array of Q15 type.    
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 
 * @ingroup groupStats    
45 
 */
46 
 
47 
/**    
48 
 * @addtogroup variance    
49 
 * @{    
50 
 */
51 
 
52 
/**    
53 
 * @brief Variance of the elements of a Q15 vector.    
54 
 * @param[in]       *pSrc points to the input vector    
55 
 * @param[in]       blockSize length of the input vector    
56 
 * @param[out]      *pResult variance value returned here    
57 
 * @return none.    
58 
 *    
59 
 * @details    
60 
 * <b>Scaling and Overflow Behavior:</b>    
61 
 *    
62 
 * \par    
63 
 * The function is implemented using a 64-bit internal accumulator.    
64 
 * The input is represented in 1.15 format.  
65 
 * Intermediate multiplication yields a 2.30 format, and this    
66 
 * result is added without saturation to a 64-bit accumulator in 34.30 format.    
67 
 * With 33 guard bits in the accumulator, there is no risk of overflow, and the    
68 
 * full precision of the intermediate multiplication is preserved.    
69 
 * Finally, the 34.30 result is truncated to 34.15 format by discarding the lower    
70 
 * 15 bits, and then saturated to yield a result in 1.15 format.    
71 
 *    
72 
 */
73 
 
74 
 
75 
void arm_var_q15(
76 
  q15_t * pSrc,
77 
  uint32_t blockSize,
78 
  q15_t * pResult)
79 
{
80 
 
81 
  q31_t sum = 0;                                 /* Accumulator */
82 
  q31_t meanOfSquares, squareOfMean;             /* square of mean and mean of square */
83 
  uint32_t blkCnt;                               /* loop counter */
84 
  q63_t sumOfSquares = 0;                        /* Accumulator */
85 
 
86 
#ifndef ARM_MATH_CM0_FAMILY
87 
 
88 
  /* Run the below code for Cortex-M4 and Cortex-M3 */
89 
 
90 
  q31_t in;                                      /* input value */
91 
  q15_t in1;                                     /* input value */
92 
 
93 
        if(blockSize == 1)
94 
        {
95 
                *pResult = 0;
96 
                return;
97 
        }
98 
 
99 
  /*loop Unrolling */
100 
  blkCnt = blockSize >> 2u;
101 
 
102 
  /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.    
103 
   ** a second loop below computes the remaining 1 to 3 samples. */
104 
  while(blkCnt > 0u)
105 
  {
106 
    /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1])  */
107 
    /* Compute Sum of squares of the input samples    
108 
     * and then store the result in a temporary variable, sum. */
109 
    in = *__SIMD32(pSrc)++;
110 
    sum += ((in << 16) >> 16);
111 
    sum += (in >> 16);
112 
    sumOfSquares = __SMLALD(in, in, sumOfSquares);
113 
    in = *__SIMD32(pSrc)++;
114 
    sum += ((in << 16) >> 16);
115 
    sum += (in >> 16);
116 
    sumOfSquares = __SMLALD(in, in, sumOfSquares);
117 
 
118 
    /* Decrement the loop counter */
119 
    blkCnt--;
120 
  }
121 
 
122 
  /* If the blockSize is not a multiple of 4, compute any remaining output samples here.    
123 
   ** No loop unrolling is used. */
124 
  blkCnt = blockSize % 0x4u;
125 
 
126 
  while(blkCnt > 0u)
127 
  {
128 
    /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
129 
    /* Compute Sum of squares of the input samples    
130 
     * and then store the result in a temporary variable, sum. */
131 
    in1 = *pSrc++;
132 
    sumOfSquares = __SMLALD(in1, in1, sumOfSquares);
133 
    sum += in1;
134 
 
135 
    /* Decrement the loop counter */
136 
    blkCnt--;
137 
  }
138 
 
139 
  /* Compute Mean of squares of the input samples    
140 
   * and then store the result in a temporary variable, meanOfSquares. */
141 
  meanOfSquares = (q31_t) (sumOfSquares / (q63_t)(blockSize - 1));
142 
 
143 
  /* Compute square of mean */
144 
  squareOfMean = (q31_t)((q63_t)sum * sum / (q63_t)(blockSize * (blockSize - 1)));
145 
 
146 
  /* mean of the squares minus the square of the mean. */
147 
  *pResult = (meanOfSquares - squareOfMean) >> 15;
148 
 
149 
#else
150 
 
151 
  /* Run the below code for Cortex-M0 */
152 
  q15_t in;                                      /* input value */
153 
 
154 
        if(blockSize == 1)
155 
        {
156 
                *pResult = 0;
157 
                return;
158 
        }
159 
 
160 
  /* Loop over blockSize number of values */
161 
  blkCnt = blockSize;
162 
 
163 
  while(blkCnt > 0u)
164 
  {
165 
    /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
166 
    /* Compute Sum of squares of the input samples    
167 
     * and then store the result in a temporary variable, sumOfSquares. */
168 
    in = *pSrc++;
169 
    sumOfSquares += (in * in);
170 
 
171 
    /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
172 
    /* Compute sum of all input values and then store the result in a temporary variable, sum. */
173 
    sum += in;
174 
 
175 
    /* Decrement the loop counter */
176 
    blkCnt--;
177 
  }
178 
 
179 
  /* Compute Mean of squares of the input samples    
180 
   * and then store the result in a temporary variable, meanOfSquares. */
181 
  meanOfSquares = (q31_t) (sumOfSquares / (q63_t)(blockSize - 1));
182 
 
183 
  /* Compute square of mean */
184 
  squareOfMean = (q31_t)((q63_t)sum * sum / (q63_t)(blockSize * (blockSize - 1)));
185 
 
186 
  /* mean of the squares minus the square of the mean. */
187 
  *pResult = (meanOfSquares - squareOfMean) >> 15;
188 
 
189 
#endif /* #ifndef ARM_MATH_CM0_FAMILY */
190 
 
191 
}
192 
 
193 
/**    
194 
 * @} end of variance group    
195 
 */