Cuda Shared Memory array variable

Question

I am trying to declare a variable for matrix multiplication as follows:

__shared__ float As[BLOCK_SIZE][BLOCK_SIZE];

I am trying to make it

Answer 1

extern __shared__ int buf[];

when you launch the kernel you should launch it this way;

kernel<<>>(...);

If you have multiple extern declaration of shared:

extern __shared__ float As[];

extern __shared__ float Bs[];

this will lead to As pointing to the same address as Bs.

You will need to keep As and Bs inside the 1D-array.

extern __shared__ float smem[];

When calling kernel, you should launch it with 2*BLOCK_SIZE*BLOCK_SIZE*sizeof(float).

When indexing into As, use smem[y*BLOCK_SIZE+x] and when indexing into Bs use smem[BLOCK_SIZE*BLOCK_SIZE+y*BLOCK_SIZE+x]