arm_mean_q31.c 4.2 KB

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  1. /* ----------------------------------------------------------------------
  2. * Copyright (C) 2010-2014 ARM Limited. All rights reserved.
  3. *
  4. * $Date: 12. March 2014
  5. * $Revision: V1.4.4
  6. *
  7. * Project: CMSIS DSP Library
  8. * Title: arm_mean_q31.c
  9. *
  10. * Description: Mean value of a Q31 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. #include "arm_math.h"
  41. /**
  42. * @ingroup groupStats
  43. */
  44. /**
  45. * @addtogroup mean
  46. * @{
  47. */
  48. /**
  49. * @brief Mean value of a Q31 vector.
  50. * @param[in] *pSrc points to the input vector
  51. * @param[in] blockSize length of the input vector
  52. * @param[out] *pResult mean value returned here
  53. * @return none.
  54. *
  55. * @details
  56. * <b>Scaling and Overflow Behavior:</b>
  57. *\par
  58. * The function is implemented using a 64-bit internal accumulator.
  59. * The input is represented in 1.31 format and is accumulated in a 64-bit
  60. * accumulator in 33.31 format.
  61. * There is no risk of internal overflow with this approach, and the
  62. * full precision of intermediate result is preserved.
  63. * Finally, the accumulator is truncated to yield a result of 1.31 format.
  64. *
  65. */
  66. void arm_mean_q31(
  67. q31_t * pSrc,
  68. uint32_t blockSize,
  69. q31_t * pResult)
  70. {
  71. q63_t sum = 0; /* Temporary result storage */
  72. uint32_t blkCnt; /* loop counter */
  73. #ifndef ARM_MATH_CM0_FAMILY
  74. /* Run the below code for Cortex-M4 and Cortex-M3 */
  75. q31_t in1, in2, in3, in4;
  76. /*loop Unrolling */
  77. blkCnt = blockSize >> 2u;
  78. /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
  79. ** a second loop below computes the remaining 1 to 3 samples. */
  80. while(blkCnt > 0u)
  81. {
  82. /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
  83. in1 = *pSrc++;
  84. in2 = *pSrc++;
  85. in3 = *pSrc++;
  86. in4 = *pSrc++;
  87. sum += in1;
  88. sum += in2;
  89. sum += in3;
  90. sum += in4;
  91. /* Decrement the loop counter */
  92. blkCnt--;
  93. }
  94. /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
  95. ** No loop unrolling is used. */
  96. blkCnt = blockSize % 0x4u;
  97. #else
  98. /* Run the below code for Cortex-M0 */
  99. /* Loop over blockSize number of values */
  100. blkCnt = blockSize;
  101. #endif /* #ifndef ARM_MATH_CM0_FAMILY */
  102. while(blkCnt > 0u)
  103. {
  104. /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
  105. sum += *pSrc++;
  106. /* Decrement the loop counter */
  107. blkCnt--;
  108. }
  109. /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) / blockSize */
  110. /* Store the result to the destination */
  111. *pResult = (q31_t) (sum / (int32_t) blockSize);
  112. }
  113. /**
  114. * @} end of mean group
  115. */