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  1. /* ----------------------------------------------------------------------
  2.  * Project:      CMSIS DSP Library
  3.  * Title:        arm_sub_f32.c
  4.  * Description:  Floating-point vector subtraction.
  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 BasicSub Vector Subtraction
  37.  *
  38.  * Element-by-element subtraction of two vectors.
  39.  *
  40.  * <pre>
  41.  *     pDst[n] = pSrcA[n] - pSrcB[n],   0 <= n < blockSize.
  42.  * </pre>
  43.  *
  44.  * There are separate functions for floating-point, Q7, Q15, and Q31 data types.
  45.  */
  46.  
  47. /**
  48.  * @addtogroup BasicSub
  49.  * @{
  50.  */
  51.  
  52.  
  53. /**
  54.  * @brief Floating-point vector subtraction.
  55.  * @param[in]       *pSrcA points to the first input vector
  56.  * @param[in]       *pSrcB points to the second input vector
  57.  * @param[out]      *pDst points to the output vector
  58.  * @param[in]       blockSize number of samples in each vector
  59.  * @return none.
  60.  */
  61.  
  62. void arm_sub_f32(
  63.   float32_t * pSrcA,
  64.   float32_t * pSrcB,
  65.   float32_t * pDst,
  66.   uint32_t blockSize)
  67. {
  68.   uint32_t blkCnt;                               /* loop counter */
  69.  
  70. #if defined (ARM_MATH_DSP)
  71.  
  72. /* Run the below code for Cortex-M4 and Cortex-M3 */
  73.   float32_t inA1, inA2, inA3, inA4;              /* temporary variables */
  74.   float32_t inB1, inB2, inB3, inB4;              /* temporary variables */
  75.  
  76.   /*loop Unrolling */
  77.   blkCnt = blockSize >> 2U;
  78.  
  79.   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
  80.    ** a second loop below computes the remaining 1 to 3 samples. */
  81.   while (blkCnt > 0U)
  82.   {
  83.     /* C = A - B */
  84.     /* Subtract and then store the results in the destination buffer. */
  85.     /* Read 4 input samples from sourceA and sourceB */
  86.     inA1 = *pSrcA;
  87.     inB1 = *pSrcB;
  88.     inA2 = *(pSrcA + 1);
  89.     inB2 = *(pSrcB + 1);
  90.     inA3 = *(pSrcA + 2);
  91.     inB3 = *(pSrcB + 2);
  92.     inA4 = *(pSrcA + 3);
  93.     inB4 = *(pSrcB + 3);
  94.  
  95.     /* dst = srcA - srcB */
  96.     /* subtract and store the result */
  97.     *pDst = inA1 - inB1;
  98.     *(pDst + 1) = inA2 - inB2;
  99.     *(pDst + 2) = inA3 - inB3;
  100.     *(pDst + 3) = inA4 - inB4;
  101.  
  102.  
  103.     /* Update pointers to process next sampels */
  104.     pSrcA += 4U;
  105.     pSrcB += 4U;
  106.     pDst += 4U;
  107.  
  108.     /* Decrement the loop counter */
  109.     blkCnt--;
  110.   }
  111.  
  112.   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
  113.    ** No loop unrolling is used. */
  114.   blkCnt = blockSize % 0x4U;
  115.  
  116. #else
  117.  
  118.   /* Run the below code for Cortex-M0 */
  119.  
  120.   /* Initialize blkCnt with number of samples */
  121.   blkCnt = blockSize;
  122.  
  123. #endif /* #if defined (ARM_MATH_DSP) */
  124.  
  125.   while (blkCnt > 0U)
  126.   {
  127.     /* C = A - B */
  128.     /* Subtract and then store the results in the destination buffer. */
  129.     *pDst++ = (*pSrcA++) - (*pSrcB++);
  130.  
  131.     /* Decrement the loop counter */
  132.     blkCnt--;
  133.   }
  134. }
  135.  
  136. /**
  137.  * @} end of BasicSub group
  138.  */
  139.