FORTRAN 90 - Insert Matrices into Other Matrices

[JP12321]

TL;DR

I need help making a matrix, with elements that contain other matrices! If you have even a basic knowledge of MATLAB then I have provided the code for this, to make it a bit more descriptive.
Thanks.

Hi,

I haven't made a code for it yet, however I will be making a Gauss-Seidel algroithm in Fortran 90, for solving very large matrices (actually to initiate the multi-gird method but that's irrelevant for this). As part of this, I wish to insert matrices into other matrices.

in MATLAB this is very simple, for example:
A=[1,2;3,4]
B=[A,A;A,A]
Outputs:
B =

1 2 1 2
3 4 3 4
1 2 1 2
3 4 3 4

However I have been having difficulties achieving the same with Fortran.

Please ignore the context - I don't require help with the GS/MG methods, I just need help embedding matrices (for other topics too), if at all possible!

Thanks in advance,

JP.

 

[jedishrfu]

Have you considered creating a 4D array where the first two indices select the matrix of interest?

Also I am assuming all the matrices are the same size.

The one problem I see that you may need to copy the selected matrix to a 2D array for use in any matrix style operations.

In C code, that would be unnecessary but I think in Fortran array storage is different and you’ll need to review that first.

 

[Dr Transport]

something to the effect:
B[1:2,1:2 ] = A[1:2,1:2]
B[1:2,3:4 ] = A[1:2,1:2]
B[3:4,1:2 ] = A[1:2,1:2]
B[3:4,3:4 ] = A[1:2,1:2]

if I remember my fortran90 correctly... ( can't find my fortran90 book right now)