Storing 3D Array on Heap as Structure Member

Question

I recently started working with C++ for numerical computations where I want to use a Struct Operators to store 3D Fields over the course of the simulation. I create the 3D arrays on the heap with

const unsigned int RES = 256;
auto arr3D = new double [RES][RES][RES];

because from what I've tested this approach is faster than using either Boost_multiarr, Eigen Tensor or nested Vectors. So far this worked fine with my minimalistic Test.cpp but when I try to implement these same 3D Arrays as Members of my Struct Operators, I cannot use the auto command anymore:

const unsigned int RES = 256;

struct Operators {
public:
    std::complex<double>*** wfc;         // edited, see 'spitconsumers' comment

    Operators(Settings &set) {        // just another structure used by Operators
        wfc = new std::complex<double> [RES][RES][RES];

        // ...Initializing wfc using Settings

};

In this case I found no way of declaring wfc, such that I do not get errors of the type

error: cannot convert 'std::complex (*)[256][256]' to 'std::complex***' in assignment

So my question is how to correctly declare the 3D Array wfc and whether maintaining this Structure approach is at all possible/useful. Would it generally be faster to access the wfc[i][j][k] if wfc was not member of a structure? (I will have to do this ~10^6 times)

Thanks in advance!

Answer 1

The error message returns the correct declaration, std::complex<double>(*wfc)[RES][RES];.

const unsigned int RES = 256;
struct Settings {};
struct Operators {
public:
    std::complex<double>(*wfc)[RES][RES];         // edited, see 'spitconsumers' comment

    Operators(Settings& set) {        // just another structure used by Operators
        wfc = new std::complex<double>[RES][RES][RES];

        // ...Initializing wfc using Settings
        // Setting the last element
        wfc[254][254[254] = 42;

    };
}