Error with atomic instructions. error: expression must have integral or enum type

Hi gys,

I am trying to use atomicAdd to add the index of a pixel to a gpu_regionOff. The code is shown below:

__global__ void calcCentroidKernel( int *gpu_labels, int *gpu_nRegions, int *gpu_regionOff, int *gpu_regionSize, int *gpu_centroid, int *i, int pitch)


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

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

    int index = x+y*pitch;

    int     j = 0;

	//// Implement this critical section with atomics. The followning code wont work... :(

	if( gpu_labels[index] == index)


		atomicAdd( i, 1);

		atomicAdd( gpu_regionOff+i, index);    /////////// ------------ At this line is the error shown --------------- //////////////


	// I dont think there is a need to __syncthreads but try it, if it doesnt work out.

	// Finding the index where offset is stored.	

	for( j=0; j < *gpu_nRegions; j++)


		if( gpu_labels[index] == gpu_regionOff[j])




	// Storing the value of centroid at 2*j position.

	if( gpu_labels[index] != -1)


		atomicAdd( gpu_centroid+(2*j), x);

		atomicAdd( gpu_centroid+(2*j)+1, y);

		atomicAdd( gpu_regionSize+j, 1);



void calcCentroid( int *gpu_labels, unsigned char *gpu_labels_uchar, int threadsX, int threadsY, int imageW, int imageH, int *gpu_nRegions, int *gpu_regionOff, int *gpu_regionSize, int *gpu_centroid)


	int *i;

	cudaMalloc( (void **)&i, sizeof(int));

	cudaMemset( i, -1, sizeof(int));

	dim3 block( threadsX, threadsY, 1);

	dim3 grid( imageW / block.x, imageH / block.y, 1);

	calcCentroidKernel<<<grid,block>>>( gpu_labels, gpu_nRegions, gpu_regionOff, gpu_regionSize, gpu_centroid, i, imageW);

int *gpu_regionOff, *gpu_regionSize, *gpu_centroid;

	cudaMalloc( (void **)&gpu_regionOff, (*nRegions)*sizeof(int));

	cudaMalloc( (void **)&gpu_regionSize, (*nRegions)*sizeof(int));

	cudaMalloc( (void **)&gpu_centroid, (*nRegions)*2*sizeof(int));

	cudaMemset( gpu_regionOff, -1, (*nRegions)*sizeof(int));

	cudaMemset( gpu_regionSize, 0, (*nRegions)*sizeof(int));

	cudaMemset( gpu_centroid, -1, (*nRegions)*2*sizeof(int));


	//////////////////////////////////////////////////// Calculating Centroid ////////////////////////////////////////////////////////

	calcCentroid( gpu_labels, gpu_labels_uchar, threadsX, threadsY, imageW, imageH, gpu_nRegions, gpu_regionOff, gpu_regionSize, gpu_centroid);

Once i compile the code the following error is shown: (I have marked the line in the code where error occurs)

error: expression must have integral or enum type

Can anyone point out what is gng wrong? Should i use cudaArray instead of global memory for gpu_regionOff,gpu_regionSize, gpu_centroid ?

I guess the line in question is supposed to read

atomicAdd( gpu_regionOff+*i, index);

as two pointers cannot be summed.

Damn… such a tiny mistake… lol

Thanks a bunch… Really appreciate the help… :biggrin: