I'm currently playing with work-group size and use the following :
globalWork = cl::NDRange(3840, 4);
localWork = cl::NDRange(32, 4);
And so, is it correct if I use the following to get the current item from a sequential array ?
int row = get_global_id(1);
int col = get_global_id(0);
size_t gid = row * get_global_size(0) + col;