Dynamic Allocation using a member in a structure

Question

I tried to allocate memory for structure members: this is the structure:

struct conserved_variables {
    double **roh;
    double **mx;
    double **my;
    double **E;
}; 

I constructed an array of this structure

conserved_variables ** U= new conserved_variables*[Ny];
for (int i = 0; i < Ny; i++)
{
    U[i] = new conserved_variables[Nx];
}

Then I tried to allocate arrays for each member in this structure:

for (int i = 0; i < Ny; i++)
        for (int j = 0; j < Nx; j++)
        {
            U[i][j].E = new double*[Order + 1];
            U[i][j].mx = new double*[Order + 1];
            U[i][j].my = new double*[Order + 1];
            U[i][j].roh = new double*[Order + 1];
            for (int k = 0; k <= Order; i++)
            {
                U[i][j].roh[k] = new double[Order + 1];
                U[i][j].mx[k] = new double[Order + 1];
                U[i][j].my[k] = new double[Order + 1];
                U[i][j].E[k] = new double[Order + 1];
            }
        }

I got this error message:

    Exception thrown at 0x01153FDD in FR_1D_Advection_Equation.exe: 0xC0000005: Access violation writing location 0xCDCDCDCD.

If there is a handler for this exception, the program may be safely continued.

Answer 1

This is a memory locality nightmare.

As for your actual bug, you were not careful with your inner loop:

for (int k = 0; k <= Order; i++)
//                          ^
//                          you mean k

This is exploding because you accidentally push i way past the bounds of the U array. It should have been easy to spot if you had spent as much time using a debugger as it took you to ask the question on Stack Overflow.