Eigensolver context

The <eigensolver> context is used to control everything related to eigenvalue solvers.

Attributes:

• mode - Controls which ARPACK method to use (integer in range [1,6]). See the <mode> tag below.

Example:

<eigensolver mode="3">
  <nev>3</nev>
  <ncv>4</ncv>
  <shift>1.0e3</shift>
</eigensolver>

The <eigensolver> context can have the following sub-contexts.

<mode>

Use this to control which ARPACK method to use.

• Attributes: None
• Value: The method to use, integer in range [1,6].

Example:

<mode>3</mode>

The value of the <mode> context has the following interpretation:

• 1 : Standard eigenvalue problem in regular mode
• 2 : Standard eigenvalue problem in shift-invert mode
• 3 : Generalized eigenvalue problem in inverse mode
• 4 : Generalized eigenvalue problem in shift-invert mode
• 5 : Generalized eigenvalue problem in buckling mode
• 5 : Generalized eigenvalue problem in Cayley mode

Mode 4 is typically used fro free vibration analsysis and mode 5 is for linearized buckling analysis. Refer to the ARPACK documentation for details on the different methods, or browse the ARPACK github repository.

<nev>

Use this to set the number of eigenvalues to compute.

• Attributes: None
• Value: The number of eigenvalues

Example:

<nev>3</nev>

<ncv>

Use this to set the number of Arnoldi vectors to compute.

• Attributes: None
• Value: The number of Arnoldi vectors

Example:

<ncv>4</ncv>

<shift>

Use this to control the eigenvalue shift (used to avoid numerical issues).

• Attributes: None
• Value: The eigenvalue shift

Example:

<shift>1.0e3</shift>