[t.oliveira]

Dear all,

I was able to write the following code that:
- creates a 3D list of scalars of size Nx x Ny x Nz
- initializes all the scalars to 0
- iterates over the 3D list varying first the coordinate of the inner list, then of the intermediate list, and then of the outer list.

This code looks ugly and unreadable. Is it possible to write it in a better way?

label Nx = 10;
label Ny = 12;
label Nz = 15;

List<List<List<scalar> > > var(Nz,List<List<scalar> >(Ny,List<scalar>(Nx,0)));

forAll(var, k)
    forAll(var[k], j)
        forAll(var[k][j], i)
            cout << k << " " << j << " " << i << " " << var[k][j][i] << "\n";

Best regards,
Thomas

[Jerryfan]

Hi Thomas,


I think it's better to stick to a 1D array or list of size Nx x Ny x Nz as in O.F., most of the field variables are defined in terms of a 1D array or list.
You can do it maybe this way to simplify your problem.

DimensionedField<scalar, volMesh> var
(
IOobject
(
"var",
runTime.timeName(),
mesh,
IOobject::MUST_READ,
IOobject::AUTO_WRITE,
false
),
mesh,
dimless,
false
);

Then, it would become easier to set all the values as well as printing the member values. Here I am assuming that your mesh size has to be Nx x Ny x Nz, with Nx cells in the x axis, y cells in the y axis and z in the z axis, respectively.

forAll (var, cellID)
{
var[cellID] = cellID;
Info<<var[cellID]<<endl;
}

[t.oliveira]

Dear Jerry,

Thank you for your time!

I need to write the values to a file in that order to interface OpenFOAM with another program, so I think I need a direct mapping between the position of the cell in a cartesian grid and the position of var in the list. That is why the OpenFOAMic syntax forAll (var, cellID) may not be appropriate in this case.

Best wishes,
Thomas

[Jerryfan]

In that case, it's easy to replace forAll with the C++ for loop.

[GerhardHolzinger]

Originally Posted by Jerryfan

In that case, it's easy to replace forAll with the C++ for loop.

The forAll statement is a macro defining a C++ for loop. forAll is just a handy shorthand.
So, there is no need to change the code from using forAll to C++'s for list syntax.

This is the definition of forAll in UList.H:

#define forAll(list, i) \
    for (Foam::label i=0; i<(list).size(); i++)

[Zeppo]

http://cpptruths.blogspot.ru/2011/10...ys-in-c11.html:

#include <iostream>
#include <array>

template <class T, size_t I, size_t... J>
struct MultiDimArray 
{
  typedef typename MultiDimArray<T, J...>::type Nested;
  typedef std::array<Nested, I> type;
};
 
template <class T, size_t I>
struct MultiDimArray<T, I> 
{
  typedef std::array<T, I> type;
};

int main()
{
    MultiDimArray<float, 2, 2, 2>::type floats {{ {{ {111,112}, {121,122} }}, 
                                                  {{ {211,212}, {221,222} }} }};
    for(size_t i=0; i<floats.size(); ++i)
    {
        for(size_t j=0; j<floats[i].size(); ++j)
        {
            for(size_t k=0; k<floats[k].size(); ++k)    
                std::cout << floats[i][j][k] << "\t";
            std::cout << endl;
        }
        std::cout << endl;
    }
}

[t.oliveira]

Dear Sergei,

Thank you! It was something like that that I was looking for.

Best regards,
Thomas