OpenACC中的运算符重载问题

I am trying to overload a simple parenthesis in the following class



   class MyClass{

    private:
    double *P;
    // some code to allocate required variables on the device on the device
    #pragma acc routine
     public:
    double &operator()( int i, int j, int k );

    }
// constructor


   MyClass::MyClass( int n )
    {
    N = n;
    P=new double[N*N*N];

    for(int i=0;i<N*N*N;i++)
    {
    P[i]=0.0;
    }
    #pragma acc enter data create(this[0:1])
    #pragma acc enter data create(P[0:N*N*N])
    #pragma acc update device(this)
    }





 #pragma acc routine
    double& MyClass::operator()(int i, int j,int k)
    {

    // some assertion to catch bugs
    //
    return P[i+N*j+N*N*k];
    }



  int main()
    {
    MyClass P1;
    // using a very simple assignment
    #pragma acc kernels
    #pragma acc loop
    for ( int i = 0; i < N; i++ )
    {
    #pragma acc loop
    for ( int j = 0; j < N; j++ )
    {
    #pragma acc loop
    for ( int k = 0; k < N; k++ )
    {

    P1( i, j, k )=2.0 ;
    }
    }
    }
    }

//编译器错误: 238,生成隐式副本(P1) 244,复杂的循环承载依赖性阻止了并行化 生成的加速器标量内核 已生成加速器内核 生成特斯拉代码 244,#pragma acc loop seq 247,#pragma acc loop seq 250,#pragma acc loop seq 247,复杂的循环承载依赖性阻止了并行化 250,复杂的循环承载依赖性阻止了并行化

传递引用与此有关吗?