KRYOPT

KRYOPT, MAXDIM, --,--, RESTOL, OrthTol
Specifies solution options for a Krylov method harmonic analysis.

SOLUTION: Dynamic Options

MAXDIM: Maximum dimension of subspace. The default size is automatically determined by the program (ranges around 50).
--, --: Unused fields.
RESTOL: Tolerance used to verify the L-2 norm values of calculated residuals and issue a warning if RESTOL is exceeded throughout the entire frequency range. Default = 0.05.
OrthTol: Tolerance that controls the orthonormality check of the Krylov subspace vectors. Valid values range from 0 to 1. The default is 1E-8.

Command Default

The default values listed for each argument above are used.

Notes

This command is used to specify solution options for a harmonic analysis solved with the Krylov method (Method = KRYLOV on HROPT, see also Frequency-Sweep Harmonic Analysis via the Krylov Method in the Structural Analysis Guide).

Increasing subspace size (MAXDIM) improves solution accuracy with the trade-off of increased computational cost and additional memory requirements.

The RESTOL and OrthTol options do not affect the accuracy of the solution. They simply control the output of messages displayed regarding the accuracy of the final computed solution or orthonormality of the computed subspace.

The program computes the condition number of a matrix created based on the dot products of the Krylov subspace vectors with each other. When the condition number of this matrix is closer to 1, it means the subspace vectors are orthonormal. When it is closer to 0, that means the subspace vectors are not orthonormal. The OrthTol value is used in the following formula to determine the orthonormality of the computed Krylov subspace: . When this condition is true, the Krylov subspace is determined to be sufficiently orthonormal, and vice versa.

Menu Paths

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