4D matrix with one non-constant dimension

[FzzPoofy]

I am having trouble figuring out how to create a 4D matrix in c++ with only one variable, and 3 constant dimensions.

I am trying to create the matrix

B[n_elements][n_shape_functions][n_integration_stations][n_dimensions]

where n_elements is read in from a file, while all the rest are hard-coded as constant.

I assume dynamic allocation is necessary, but I am not sure how to approach this.

(For reference, I use a Mac and code in Xcode)

Thanks!

[Duthomhas]

Use the STL to your advantage: use a deque or vector. You can initialize the size of any of them.

[FzzPoofy]

I'm a beginner with c++, I haven't learned about stl yet. Do you have a suggestion for a good reference to learn the ins and outs of it?

[gaorozcoo]

Hi,

Please try this and tell me if it works for you

* To create the array

int (*pointer)[n_shape_functions][n_integration_stations][n_dimensions] = new int[readValueFromFile][n_shape_functions][n_integration_stations][n_dimensions];

* To use the array you need to do something like this:

for(i=0; i<readValueFromFile; i++){
        for(j=0; j<n_shape_functions; j++)
               for(k=0; k<n_integration_stations; k++)
                      for(l=0; l<n_dimensions; l++)
                            pointer[i][j][k][l]=0;

[FzzPoofy]

Seems to work fine. THANKS SO MUCH!

[Duthomhas]

I learned something amazing!

[D80DSL3A]

One last step!! Don.t forget to release the dynamically allocated memory when you are done with it else a memory leak results.
delete [] pointer;

I wrote a complete program to post here but it uses the same method that gaorozcoo presented.
Oops, too late!

[FzzPoofy]

Thanks for all the "pointers" everyone. (Had to do it.)

I appreciate the help!

[FzzPoofy]

Update: I've been using this constantly in my code. This is so much easier that what I had been doing!