关于matlab和cuda混合编程的一些困惑

Question

通过VS2015创建的.cu文件里面包括了在GPU上调用的global函数以及mexfunction。
之后直接在matlab里面通过mexcuda XX.cu命令就可以生成可以在matlab直接调用
并且通过GPU加速的mexw64吗？
为什么matlab带的demo里面还有一些诸如mxgpu， mxGPUCreateFromMxArray的东西，感觉搞不懂了，有点混乱！

 /*
 * Example of how to use the mxGPUArray API in a MEX file.  This example shows
 * how to write a MEX function that takes a gpuArray input and returns a
 * gpuArray output, e.g. B=mexFunction(A).
 *
 * Copyright 2012 The MathWorks, Inc.
 */

#include "mex.h"
#include "gpu/mxGPUArray.h"

/*
 * Device code
 */
void __global__ TimesTwo(double const * const A,
                         double * const B,
                         int const N)
{
    /* Calculate the global linear index, assuming a 1-d grid. */
    int const i = blockDim.x * blockIdx.x + threadIdx.x;
    if (i < N) {
        B[i] = 2.0 * A[i];
    }
}

/*
 * Host code
 */
void mexFunction(int nlhs, mxArray *plhs[],
                 int nrhs, mxArray const *prhs[])
{
    /* Declare all variables.*/
    mxGPUArray const *A;
    mxGPUArray *B;
    double const *d_A;
    double *d_B;
    int N;



    int const threadsPerBlock = 256;
    int blocksPerGrid;

    /* Initialize the MathWorks GPU API. */
    mxInitGPU();



    A = mxGPUCreateFromMxArray(prhs[0]);



    /*
     * Now that we have verified the data type, extract a pointer to the input
     * data on the device.
     */
    d_A = (double const *)(mxGPUGetDataReadOnly(A));

    /* Create a GPUArray to hold the result and get its underlying pointer. */
    B = mxGPUCreateGPUArray(mxGPUGetNumberOfDimensions(A),
                            mxGPUGetDimensions(A),
                            mxGPUGetClassID(A),
                            mxGPUGetComplexity(A),
                            MX_GPU_DO_NOT_INITIALIZE);
    d_B = (double *)(mxGPUGetData(B));

    N = (int)(mxGPUGetNumberOfElements(A));
    blocksPerGrid = (N + threadsPerBlock - 1) / threadsPerBlock;
    TimesTwo<<<blocksPerGrid, threadsPerBlock>>>(d_A, d_B, N);

    /* Wrap the result up as a MATLAB gpuArray for return. */
    plhs[0] = mxGPUCreateMxArrayOnGPU(B);

    /*
     * The mxGPUArray pointers are host-side structures that refer to device
     * data. These must be destroyed before leaving the MEX function.
     */
    mxGPUDestroyGPUArray(A);
    mxGPUDestroyGPUArray(B);
}

Answer 1

而看到有些书里面是
先将.cu文件编译成.obj文件，然后再将一个mexfunction链接到生成的.obj文件上，最终生成可以在matlab调用的mexw64文件。