How to count the element in block

Accelerated Computing CUDA CUDA Programming and Performance
4

It works !

No need to divided to be 4 blocks

__global__ void nupspin(double **A, int *a)

{

	int x = threadIdx.x + blockIdx.x * blockDim.x;

    	int y = threadIdx.y + blockIdx.y * blockDim.y;

	if(A[x][y] == 5){

		atomicAdd(a,1);

		__syncthreads();

	}

}

Result

============GPU===============

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0

1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0

2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0

3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0

4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0

5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0

6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0

7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0

We have 5, 6 elements.

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