lib/main/CMSIS/DSP/Source/BasicMathFunctions/arm_scale_f32.c

   1 /* ----------------------------------------------------------------------
   2  * Project:      CMSIS DSP Library
   3  * Title:        arm_scale_f32.c
   4  * Description:  Multiplies a floating-point vector by a scalar
   5  *
   6  * $Date:        27. January 2017
   7  * $Revision:    V.1.5.1
   8  *
   9  * Target Processor: Cortex-M cores
  10  * -------------------------------------------------------------------- */
  11 /*
  12  * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
  13  *
  14  * SPDX-License-Identifier: Apache-2.0
  15  *
  16  * Licensed under the Apache License, Version 2.0 (the License); you may
  17  * not use this file except in compliance with the License.
  18  * You may obtain a copy of the License at
  19  *
  20  * www.apache.org/licenses/LICENSE-2.0
  21  *
  22  * Unless required by applicable law or agreed to in writing, software
  23  * distributed under the License is distributed on an AS IS BASIS, WITHOUT
  24  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  25  * See the License for the specific language governing permissions and
  26  * limitations under the License.
  27  */
  28
  29 #include "arm_math.h"
  30
  31 /**
  32  * @ingroup groupMath
  33  */
  34
  35 /**
  36  * @defgroup scale Vector Scale
  37  *
  38  * Multiply a vector by a scalar value.  For floating-point data, the algorithm used is:
  39  *
  40  * <pre>
  41  *     pDst[n] = pSrc[n] * scale,   0 <= n < blockSize.
  42  * </pre>
  43  *
  44  * In the fixed-point Q7, Q15, and Q31 functions, <code>scale</code> is represented by
  45  * a fractional multiplication <code>scaleFract</code> and an arithmetic shift <code>shift</code>.
  46  * The shift allows the gain of the scaling operation to exceed 1.0.
  47  * The algorithm used with fixed-point data is:
  48  *
  49  * <pre>
  50  *     pDst[n] = (pSrc[n] * scaleFract) << shift,   0 <= n < blockSize.
  51  * </pre>
  52  *
  53  * The overall scale factor applied to the fixed-point data is
  54  * <pre>
  55  *     scale = scaleFract * 2^shift.
  56  * </pre>
  57  *
  58  * The functions support in-place computation allowing the source and destination
  59  * pointers to reference the same memory buffer.
  60  */
  61
  62 /**
  63  * @addtogroup scale
  64  * @{
  65  */
  66
  67 /**
  68  * @brief Multiplies a floating-point vector by a scalar.
  69  * @param[in]       *pSrc points to the input vector
  70  * @param[in]       scale scale factor to be applied
  71  * @param[out]      *pDst points to the output vector
  72  * @param[in]       blockSize number of samples in the vector
  73  * @return none.
  74  */
  75
  76
  77 void arm_scale_f32(
  78   float32_t * pSrc,
  79   float32_t scale,
  80   float32_t * pDst,
  81   uint32_t blockSize)
  82 {
  83   uint32_t blkCnt;                               /* loop counter */
  84 #if defined (ARM_MATH_DSP)
  85
  86 /* Run the below code for Cortex-M4 and Cortex-M3 */
  87   float32_t in1, in2, in3, in4;                  /* temporary variabels */
  88
  89   /*loop Unrolling */
  90   blkCnt = blockSize >> 2U;
  91
  92   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
  93    ** a second loop below computes the remaining 1 to 3 samples. */
  94   while (blkCnt > 0U)
  95   {
  96     /* C = A * scale */
  97     /* Scale the input and then store the results in the destination buffer. */
  98     /* read input samples from source */
  99     in1 = *pSrc;
 100     in2 = *(pSrc + 1);
 101
 102     /* multiply with scaling factor */
 103     in1 = in1 * scale;
 104
 105     /* read input sample from source */
 106     in3 = *(pSrc + 2);
 107
 108     /* multiply with scaling factor */
 109     in2 = in2 * scale;
 110
 111     /* read input sample from source */
 112     in4 = *(pSrc + 3);
 113
 114     /* multiply with scaling factor */
 115     in3 = in3 * scale;
 116     in4 = in4 * scale;
 117     /* store the result to destination */
 118     *pDst = in1;
 119     *(pDst + 1) = in2;
 120     *(pDst + 2) = in3;
 121     *(pDst + 3) = in4;
 122
 123     /* update pointers to process next samples */
 124     pSrc += 4U;
 125     pDst += 4U;
 126
 127     /* Decrement the loop counter */
 128     blkCnt--;
 129   }
 130
 131   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
 132    ** No loop unrolling is used. */
 133   blkCnt = blockSize % 0x4U;
 134
 135 #else
 136
 137   /* Run the below code for Cortex-M0 */
 138
 139   /* Initialize blkCnt with number of samples */
 140   blkCnt = blockSize;
 141
 142 #endif /* #if defined (ARM_MATH_DSP) */
 143
 144   while (blkCnt > 0U)
 145   {
 146     /* C = A * scale */
 147     /* Scale the input and then store the result in the destination buffer. */
 148     *pDst++ = (*pSrc++) * scale;
 149
 150     /* Decrement the loop counter */
 151     blkCnt--;
 152   }
 153 }
 154
 155 /**
 156  * @} end of scale group
 157  */