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  1. /* ----------------------------------------------------------------------
  2.  * Project:      CMSIS DSP Library
  3.  * Title:        arm_dot_prod_q31.c
  4.  * Description:  Q31 dot product
  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.  * @addtogroup dot_prod
  37.  * @{
  38.  */
  39.  
  40. /**
  41.  * @brief Dot product of Q31 vectors.
  42.  * @param[in]       *pSrcA points to the first input vector
  43.  * @param[in]       *pSrcB points to the second input vector
  44.  * @param[in]       blockSize number of samples in each vector
  45.  * @param[out]      *result output result returned here
  46.  * @return none.
  47.  *
  48.  * <b>Scaling and Overflow Behavior:</b>
  49.  * \par
  50.  * The intermediate multiplications are in 1.31 x 1.31 = 2.62 format and these
  51.  * are truncated to 2.48 format by discarding the lower 14 bits.
  52.  * The 2.48 result is then added without saturation to a 64-bit accumulator in 16.48 format.
  53.  * There are 15 guard bits in the accumulator and there is no risk of overflow as long as
  54.  * the length of the vectors is less than 2^16 elements.
  55.  * The return result is in 16.48 format.
  56.  */
  57.  
  58. void arm_dot_prod_q31(
  59.   q31_t * pSrcA,
  60.   q31_t * pSrcB,
  61.   uint32_t blockSize,
  62.   q63_t * result)
  63. {
  64.   q63_t sum = 0;                                 /* Temporary result storage */
  65.   uint32_t blkCnt;                               /* loop counter */
  66.  
  67.  
  68. #if defined (ARM_MATH_DSP)
  69.  
  70. /* Run the below code for Cortex-M4 and Cortex-M3 */
  71.   q31_t inA1, inA2, inA3, inA4;
  72.   q31_t inB1, inB2, inB3, inB4;
  73.  
  74.   /*loop Unrolling */
  75.   blkCnt = blockSize >> 2U;
  76.  
  77.   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
  78.    ** a second loop below computes the remaining 1 to 3 samples. */
  79.   while (blkCnt > 0U)
  80.   {
  81.     /* C = A[0]* B[0] + A[1]* B[1] + A[2]* B[2] + .....+ A[blockSize-1]* B[blockSize-1] */
  82.     /* Calculate dot product and then store the result in a temporary buffer. */
  83.     inA1 = *pSrcA++;
  84.     inA2 = *pSrcA++;
  85.     inA3 = *pSrcA++;
  86.     inA4 = *pSrcA++;
  87.     inB1 = *pSrcB++;
  88.     inB2 = *pSrcB++;
  89.     inB3 = *pSrcB++;
  90.     inB4 = *pSrcB++;
  91.  
  92.     sum += ((q63_t) inA1 * inB1) >> 14U;
  93.     sum += ((q63_t) inA2 * inB2) >> 14U;
  94.     sum += ((q63_t) inA3 * inB3) >> 14U;
  95.     sum += ((q63_t) inA4 * inB4) >> 14U;
  96.  
  97.     /* Decrement the loop counter */
  98.     blkCnt--;
  99.   }
  100.  
  101.   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
  102.    ** No loop unrolling is used. */
  103.   blkCnt = blockSize % 0x4U;
  104.  
  105. #else
  106.  
  107.   /* Run the below code for Cortex-M0 */
  108.  
  109.   /* Initialize blkCnt with number of samples */
  110.   blkCnt = blockSize;
  111.  
  112. #endif /* #if defined (ARM_MATH_DSP) */
  113.  
  114.  
  115.   while (blkCnt > 0U)
  116.   {
  117.     /* C = A[0]* B[0] + A[1]* B[1] + A[2]* B[2] + .....+ A[blockSize-1]* B[blockSize-1] */
  118.     /* Calculate dot product and then store the result in a temporary buffer. */
  119.     sum += ((q63_t) * pSrcA++ * *pSrcB++) >> 14U;
  120.  
  121.     /* Decrement the loop counter */
  122.     blkCnt--;
  123.   }
  124.  
  125.   /* Store the result in the destination buffer in 16.48 format */
  126.   *result = sum;
  127. }
  128.  
  129. /**
  130.  * @} end of dot_prod group
  131.  */
  132.