LANBOPTION
LANBOPTION,
StrmCk, --,
AltMeth, Memory_Option
Specifies Block Lanczos eigensolver options.
StrmCkControls whether the Block Lanczos eigensolver will perform a Sturm sequence check:
OFF
—
Do not perform the Sturm sequence check (default).
ON
—
Perform a Sturm sequence check. This requires additional matrix factorization (which can be expensive), but does help ensure that no modes are missed in the specified range.
--Unused field.
AltMethALT1
—
Alternative version of the Block Lanczos eigensolver for more difficult modal or buckling problems. This version of Block Lanczos only runs in shared-memory parallel (SMP) mode. If the analysis is run in distributed-memory parallel (DMP) mode, it will switch to SMP mode when this Alternative Block Lanczos solver is invoked, and resume in DMP mode after the eigensolution.
Memory_OptionMemory allocation option:
DEFAULT
—
Default memory configuration (default). Everything is determined dynamically with respect to current machine resources.
INCORE
—
Fully in-core memory configuration.
MIX1
—
First level of mixed in-core / out-of-core configuration.
MIX2
—
Second level of mixed in-core / out-of-core configuration.
OUTOFCORE
—
Fully out-of-core memory configuration.
Command Default
The Sturm sequence check is off for the Block Lanczos eigensolver when it is used in a modal analysis, and on when it is used in a buckling analysis.
The default memory allocation strategy is used. Mechanical APDL evaluates the resources of the machine to choose the in-core or out-of-core mode.
Notes
LANBOPTION specifies options to be used with the Block Lanczos eigensolver during an eigenvalue buckling analysis (BUCOPT,LANB) or a modal analysis (MODOPT,LANB).
For more difficult eigenproblems, AltMeth
= ALT1 could achieve better converged eigensolutions at the cost of more computing time. This
ALT1 option is useful for double-checking solution accuracy. It should be used for difficult
eigenproblems like those with many duplicated eigenmodes, or eigen-buckling problems with very
thin beam/shell structures.
Memory Allocation Option
The Block Lanczos eigensolver algorithm allocates two main pools of memory:
Memory for the internal sparse solver iterations.
Memory for the specific Lanczos working arrays.
The following table shows how memory is allocated for each option.
Memory_Option | Sparse Solver | Working Arrays |
|---|---|---|
| INCORE | In-Core | In-Core |
| MIX1 | In-Core | Out-of-Core |
| MIX2 | Out-of-Core | In-Core |
| OUTOFCORE | Out-of-Core | Out-of-Core |
The MIX1 configuration typically uses more memory than the MIX2 configuration, except when a large number of modes are requested for a small model.