lib/main/CMSIS/DSP/Source/BasicMathFunctions/arm_dot_prod_q31.c

   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  */