cudaMallocPitch 主要起什么作用？
实现存储器空间对齐
很多应用中尤其是CC>=1.2的硬件中，不再是必须的，作用也不是很大，且往往可以通过内核中“显式”的使用half-warp或warp模式合并访寸序列
cudaError_t cudaMallocPitch ( void ** devPtr,
size_t * pitch,
size_t width,
size_t height
)
Allocates at least widthInBytes * height bytes of linear memory on the device and returns in *devPtr a pointer to the allocated memory. The function may pad the allocation to ensure that corresponding pointers in any given row will continue to meet the alignment requirements for coalescing as the address is updated from row to row. The pitch returned in *pitch by cudaMallocPitch() is the width in bytes of the allocation. The intended usage of pitch is as a separate parameter of the allocation, used to compute addresses within the 2D array. Given the row and column of an array element of type T, the address is computed as:
T* pElement = (T*)((char*)BaseAddress + Row * pitch) + Column;
For allocations of 2D arrays, it is recommended that programmers consider performing pitch allocations using cudaMallocPitch(). Due to pitch alignment restrictions in the hardware, this is especially true if the application will be performing 2D memory copies between different regions of device memory (whether linear memory or CUDA arrays).