了解CUDA中的矩阵乘法

Question

I am trying to learn CUDA. I started to try matrix multiplication with the help of this article based on GPU. My main problem is that I am unable too understand how to access 2D array in Kernel since accessing a 2D array is a bit different than the conventional method (matrix[i][j]). This is the part where i am stuck:

for (int i = 0; i < N; i++) {
    tmpSum += A[ROW * N + i] * B[i * N + COL];
}
C[ROW * N + COL] = tmpSum;

I could understand how ROW and COLUMN were derived.

int ROW = blockIdx.y*blockDim.y+threadIdx.y;
int COL = blockIdx.x*blockDim.x+threadIdx.x;

Any explanation with an example is highly appreciated. Thanks!

Answer 1

Matrices are stored contiguously, ie every row after the other at consecutive locations. What you see here is called flat adressing, ie turning the two element index to an offset from the first element.