Eigenvectors in the vectorial case

General Discussion
1

Dear all,

In 2D elasticity, if Th is the mesh on a domain, then an eigenvector is an array in “fespace Vh(Th, [P2,P2])”.
If nev is an integer and “Vh[int] eVu,eVv” is intended to store the eigenvectors the line

ncev = EigenValue(A, B, value=ev, vector=[eVu,eVv], tol=1e-18, maxit=0, ncv=0);

gives an error message, while

ncev = EigenValue(A, B, value=ev, vector=eVu, tol=1e-18, maxit=0, ncv=0);

works.

The question is : what exactly contains eVu ? and how can we recover from eVu the two components of the eigenvector ?

Thank you,
Alex

2

There are some FreeFEM syntax errors and the correct part of code is as follows:

...
Vh[int] [eVu, eVv](nev);
...
EigenValue(A, B, value=ev, vector=eVu, ...);

In addition, the ARPACK interface (EigenValue) is very old and SLEPc (EPSSolve) is suggested.

3

Thank you ! Actually, this is not mentioned in the FreeFEM documentation…
Do you have a simple example which do not use MPI ?

4

You’ll have to use FreeFem++-mpi, but you can use a single process, which will not require changes in your code. And I don’t know what you are talking about, but SLEPc is indeed mentioned in the documentation: PETSc and SLEPc.