矢量化矩阵乘法 - 2023.2 简体中文

AI 引擎内核与计算图编程指南 (UG1079)

Document ID
UG1079
Release Date
2023-12-04
Version
2023.2 简体中文
以下示例演示的矩阵乘法采用 (64 * 64) x (64 * 64) 的矩阵大小和 int8 x int8 数据类型。矩阵乘法形状为 4*16*8。对于矩阵乘法,输入数据形状经过重塑。
const int SHIFT=10;

//For element mmul
const int M=4;
const int K=16;
const int N=8;

//Total matrix sizes
const int rowA=64;
const int colA=64;
const int colB=64;

//mmul numbers
const int num_rowA=rowA/M;
const int num_colA=colA/K;
const int num_colB=colB/N;

void matrix_mul(input_buffer<int8> & __restrict matA, input_buffer<int8> & __restrict matB, output_buffer<int8> & __restrict matC){
  using MMUL = aie::mmul<M, K, N, int8, int8>;

  const int8* __restrict pA=(int8*)matA.data();
  const int8* __restrict pB=(int8*)matB.data();
  int8* __restrict pC=(int8*)matC.data();
  //For profiling only 
  unsigned cycle_num[2];
  aie::tile tile=aie::tile::current();
  cycle_num[0]=tile.cycles();//cycle counter of the AI Engine tile

  for (unsigned i = 0; i < num_rowA; i++) { //for output row number of element matrix
    for (unsigned j = 0; j < num_colB; j++) { //for output col number of element matrix
      const int8 * __restrict pA1 = pA + ( i * num_colA + 0) * MMUL::size_A;
      const int8 * __restrict pB1 = pB + ( 0 * num_colB + j) * MMUL::size_B;

      aie::vector<int8, MMUL::size_A> A0 = aie::load_v<MMUL::size_A>(pA1); pA1 += MMUL::size_A;
      aie::vector<int8, MMUL::size_B> B0 = aie::load_v<MMUL::size_B>(pB1); pB1 += MMUL::size_B * num_colB;

      MMUL C00; C00.mul(A0, B0);

      for (unsigned k = 0; k < num_colA-1; k++) {
        A0 = aie::load_v<MMUL::size_A>(pA1); pA1 += MMUL::size_A;
        B0 = aie::load_v<MMUL::size_B>(pB1); pB1 += MMUL::size_B * num_colB;
        C00.mac(A0, B0);
      }

      aie::store_v(pC, C00.template to_vector<int8>(SHIFT)); pC += MMUL::size_C;
    }
  }
  //For profiling only 
  cycle_num[1]=tile.cycles();//cycle counter of the AI Engine tile
  printf("start=%d,end=%d,total=%d\n",cycle_num[0],cycle_num[1],cycle_num[1]-cycle_num[0]);

}

剖析结果显示,此循环需耗时约 3888 个周期。对于 int8*int8 数据类型,总计执行 64*64*64=262144 次乘法,即,每个周期 262144/3888 ~=67 int8*int8 次 MAC 运算。

请注意,以上结果使用 aiecompiler 的默认设置,这将自动为循环执行循环流水打拍等最优化操作。