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1 /* ----------------------------------------------------------------------
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2 * Copyright (C) 2010-2014 ARM Limited. All rights reserved.
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3 *
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4 * $Date: 19. March 2015
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5 * $Revision: V.1.4.5
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6 *
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7 * Project: CMSIS DSP Library
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8 * Title: arm_scale_f32.c
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9 *
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10 * Description: Multiplies a floating-point vector by a scalar.
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11 *
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12 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
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13 *
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14 * Redistribution and use in source and binary forms, with or without
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15 * modification, are permitted provided that the following conditions
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16 * are met:
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17 * - Redistributions of source code must retain the above copyright
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18 * notice, this list of conditions and the following disclaimer.
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19 * - Redistributions in binary form must reproduce the above copyright
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20 * notice, this list of conditions and the following disclaimer in
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21 * the documentation and/or other materials provided with the
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22 * distribution.
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23 * - Neither the name of ARM LIMITED nor the names of its contributors
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24 * may be used to endorse or promote products derived from this
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25 * software without specific prior written permission.
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26 *
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27 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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28 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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29 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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30 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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31 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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32 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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33 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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34 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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35 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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37 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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38 * POSSIBILITY OF SUCH DAMAGE.
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39 * ---------------------------------------------------------------------------- */
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40
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41 #include "arm_math.h"
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42
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43 /**
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44 * @ingroup groupMath
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45 */
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46
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47 /**
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48 * @defgroup scale Vector Scale
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49 *
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50 * Multiply a vector by a scalar value. For floating-point data, the algorithm used is:
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51 *
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52 * <pre>
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53 * pDst[n] = pSrc[n] * scale, 0 <= n < blockSize.
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54 * </pre>
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55 *
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56 * In the fixed-point Q7, Q15, and Q31 functions, <code>scale</code> is represented by
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57 * a fractional multiplication <code>scaleFract</code> and an arithmetic shift <code>shift</code>.
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58 * The shift allows the gain of the scaling operation to exceed 1.0.
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59 * The algorithm used with fixed-point data is:
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60 *
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61 * <pre>
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62 * pDst[n] = (pSrc[n] * scaleFract) << shift, 0 <= n < blockSize.
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63 * </pre>
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64 *
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65 * The overall scale factor applied to the fixed-point data is
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66 * <pre>
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67 * scale = scaleFract * 2^shift.
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68 * </pre>
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69 *
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70 * The functions support in-place computation allowing the source and destination
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71 * pointers to reference the same memory buffer.
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72 */
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73
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74 /**
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75 * @addtogroup scale
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76 * @{
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77 */
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78
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79 /**
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80 * @brief Multiplies a floating-point vector by a scalar.
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81 * @param[in] *pSrc points to the input vector
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82 * @param[in] scale scale factor to be applied
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83 * @param[out] *pDst points to the output vector
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84 * @param[in] blockSize number of samples in the vector
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85 * @return none.
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86 */
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87
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88
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89 void arm_scale_f32(
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90 float32_t * pSrc,
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91 float32_t scale,
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92 float32_t * pDst,
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93 uint32_t blockSize)
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94 {
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95 uint32_t blkCnt; /* loop counter */
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96 #ifndef ARM_MATH_CM0_FAMILY
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97
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98 /* Run the below code for Cortex-M4 and Cortex-M3 */
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99 float32_t in1, in2, in3, in4; /* temporary variabels */
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100
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101 /*loop Unrolling */
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102 blkCnt = blockSize >> 2u;
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103
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104 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
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105 ** a second loop below computes the remaining 1 to 3 samples. */
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106 while(blkCnt > 0u)
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107 {
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108 /* C = A * scale */
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109 /* Scale the input and then store the results in the destination buffer. */
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110 /* read input samples from source */
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111 in1 = *pSrc;
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112 in2 = *(pSrc + 1);
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113
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114 /* multiply with scaling factor */
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115 in1 = in1 * scale;
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116
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117 /* read input sample from source */
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118 in3 = *(pSrc + 2);
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119
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120 /* multiply with scaling factor */
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121 in2 = in2 * scale;
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122
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123 /* read input sample from source */
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124 in4 = *(pSrc + 3);
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125
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126 /* multiply with scaling factor */
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127 in3 = in3 * scale;
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128 in4 = in4 * scale;
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129 /* store the result to destination */
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130 *pDst = in1;
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131 *(pDst + 1) = in2;
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132 *(pDst + 2) = in3;
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133 *(pDst + 3) = in4;
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134
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135 /* update pointers to process next samples */
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136 pSrc += 4u;
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137 pDst += 4u;
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138
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139 /* Decrement the loop counter */
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140 blkCnt--;
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141 }
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142
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143 /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
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144 ** No loop unrolling is used. */
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145 blkCnt = blockSize % 0x4u;
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146
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147 #else
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148
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149 /* Run the below code for Cortex-M0 */
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150
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151 /* Initialize blkCnt with number of samples */
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152 blkCnt = blockSize;
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153
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154 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
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155
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156 while(blkCnt > 0u)
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157 {
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158 /* C = A * scale */
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159 /* Scale the input and then store the result in the destination buffer. */
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160 *pDst++ = (*pSrc++) * scale;
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161
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162 /* Decrement the loop counter */
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163 blkCnt--;
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164 }
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165 }
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166
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167 /**
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168 * @} end of scale group
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169 */
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