Casting float* to char* while looping over a 2-D array in linear memory on device

Question

On Page 21 of the CUDA 4.0 programming guide there is an example (given below) to illustrate looping over the elements of a 2D array of floats in device memory. The dimensi

Answer 1

The cast is just to make the pointer arithmetic work right;

(float*)((char*)devPtr + r * pitch);

moves r*pitch bytes forward while

(float*)(devPtr + r * pitch);

would move r*pitch floats forward (ie 4 times as many bytes)