arm_mean_q7.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_q7.c
  9. *
  10. * Description: Mean value of a Q7 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 Q7 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 32-bit internal accumulator.
  59. * The input is represented in 1.7 format and is accumulated in a 32-bit
  60. * accumulator in 25.7 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 1.7 format.
  64. *
  65. */
  66. void arm_mean_q7(
  67. q7_t * pSrc,
  68. uint32_t blockSize,
  69. q7_t * pResult)
  70. {
  71. q31_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 in;
  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. in = *__SIMD32(pSrc)++;
  84. sum += ((in << 24) >> 24);
  85. sum += ((in << 16) >> 24);
  86. sum += ((in << 8) >> 24);
  87. sum += (in >> 24);
  88. /* Decrement the loop counter */
  89. blkCnt--;
  90. }
  91. /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
  92. ** No loop unrolling is used. */
  93. blkCnt = blockSize % 0x4u;
  94. #else
  95. /* Run the below code for Cortex-M0 */
  96. /* Loop over blockSize number of values */
  97. blkCnt = blockSize;
  98. #endif /* #ifndef ARM_MATH_CM0_FAMILY */
  99. while(blkCnt > 0u)
  100. {
  101. /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
  102. sum += *pSrc++;
  103. /* Decrement the loop counter */
  104. blkCnt--;
  105. }
  106. /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) / blockSize */
  107. /* Store the result to the destination */
  108. *pResult = (q7_t) (sum / (int32_t) blockSize);
  109. }
  110. /**
  111. * @} end of mean group
  112. */