arm_scale_f32.c 5.3 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_scale_f32.c
  9. *
  10. * Description: Multiplies a floating-point vector by a scalar.
  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 groupMath
  43. */
  44. /**
  45. * @defgroup scale Vector Scale
  46. *
  47. * Multiply a vector by a scalar value. For floating-point data, the algorithm used is:
  48. *
  49. * <pre>
  50. * pDst[n] = pSrc[n] * scale, 0 <= n < blockSize.
  51. * </pre>
  52. *
  53. * In the fixed-point Q7, Q15, and Q31 functions, <code>scale</code> is represented by
  54. * a fractional multiplication <code>scaleFract</code> and an arithmetic shift <code>shift</code>.
  55. * The shift allows the gain of the scaling operation to exceed 1.0.
  56. * The algorithm used with fixed-point data is:
  57. *
  58. * <pre>
  59. * pDst[n] = (pSrc[n] * scaleFract) << shift, 0 <= n < blockSize.
  60. * </pre>
  61. *
  62. * The overall scale factor applied to the fixed-point data is
  63. * <pre>
  64. * scale = scaleFract * 2^shift.
  65. * </pre>
  66. *
  67. * The functions support in-place computation allowing the source and destination
  68. * pointers to reference the same memory buffer.
  69. */
  70. /**
  71. * @addtogroup scale
  72. * @{
  73. */
  74. /**
  75. * @brief Multiplies a floating-point vector by a scalar.
  76. * @param[in] *pSrc points to the input vector
  77. * @param[in] scale scale factor to be applied
  78. * @param[out] *pDst points to the output vector
  79. * @param[in] blockSize number of samples in the vector
  80. * @return none.
  81. */
  82. void arm_scale_f32(
  83. float32_t * pSrc,
  84. float32_t scale,
  85. float32_t * pDst,
  86. uint32_t blockSize)
  87. {
  88. uint32_t blkCnt; /* loop counter */
  89. #ifndef ARM_MATH_CM0_FAMILY
  90. /* Run the below code for Cortex-M4 and Cortex-M3 */
  91. float32_t in1, in2, in3, in4; /* temporary variabels */
  92. /*loop Unrolling */
  93. blkCnt = blockSize >> 2u;
  94. /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
  95. ** a second loop below computes the remaining 1 to 3 samples. */
  96. while(blkCnt > 0u)
  97. {
  98. /* C = A * scale */
  99. /* Scale the input and then store the results in the destination buffer. */
  100. /* read input samples from source */
  101. in1 = *pSrc;
  102. in2 = *(pSrc + 1);
  103. /* multiply with scaling factor */
  104. in1 = in1 * scale;
  105. /* read input sample from source */
  106. in3 = *(pSrc + 2);
  107. /* multiply with scaling factor */
  108. in2 = in2 * scale;
  109. /* read input sample from source */
  110. in4 = *(pSrc + 3);
  111. /* multiply with scaling factor */
  112. in3 = in3 * scale;
  113. in4 = in4 * scale;
  114. /* store the result to destination */
  115. *pDst = in1;
  116. *(pDst + 1) = in2;
  117. *(pDst + 2) = in3;
  118. *(pDst + 3) = in4;
  119. /* update pointers to process next samples */
  120. pSrc += 4u;
  121. pDst += 4u;
  122. /* Decrement the loop counter */
  123. blkCnt--;
  124. }
  125. /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
  126. ** No loop unrolling is used. */
  127. blkCnt = blockSize % 0x4u;
  128. #else
  129. /* Run the below code for Cortex-M0 */
  130. /* Initialize blkCnt with number of samples */
  131. blkCnt = blockSize;
  132. #endif /* #ifndef ARM_MATH_CM0_FAMILY */
  133. while(blkCnt > 0u)
  134. {
  135. /* C = A * scale */
  136. /* Scale the input and then store the result in the destination buffer. */
  137. *pDst++ = (*pSrc++) * scale;
  138. /* Decrement the loop counter */
  139. blkCnt--;
  140. }
  141. }
  142. /**
  143. * @} end of scale group
  144. */