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~~NOTOC~~
===== Solver ComputeEigenValues =====

==== General Informations ====
  * **Solver Fortran File:** ''ComputeEigenValues.f90''
  * **Solver Name:** ''ComputeEigenValues''
  * **Required Output Variable(s):** default is ''EigenStress'' (else in ''EigenValue Variable Name'')  
  * **Required Input Variable(s):** A tensor in ''Tensor Variable Name''
  * **Optional Output Variable(s):** ''EigenVector1'', ''EigenVector2'' and ''EigenVector3''
  * **Optional Input Variable(s):** None


==== General Description ====
The aim of this solver is to compute the eigenvalues of a tensor variable (e.g., strain-rate or stress tensors). Optionnaly, the 3 eigenvectors corresponding to each of the three eigenvalues can be computed. 
 

==== SIF contents ====
The required keywords in the SIF file for this solver are:

<code>
Solver 3
  Equation = "EigenSR"
  Variable = -nooutput dumy
  Variable DOFs = 1

  Procedure = "ElmerIceSolvers" "ComputeEigenValues"

! 3 Eigenvalues    
  Exported Variable 1 = "EigenSR"
  EigenValue Variable Name = String "EigenSR"
  Tensor Variable Name = String "StrainRate"
  Exported Variable 1 DOFS = 3

! Principal vectors (optional) 
  Exported Variable 2 = EigenVector1
  Exported Variable 2 DOFS = 3
  Exported Variable 3 = EigenVector2
  Exported Variable 3 DOFS =  3
  Exported Variable 4 = EigenVector3
  Exported Variable 4 DOFS = 3
End
</code>

==== Examples ====
An example in which the eigenvalues and eigenvectors of the strain-rate tensor are computed can be found here ''[ELMER_TRUNK]/elmerice/examples/Test_StrainRate''.