PS Card

This card is for general program control such as storing the currents for re-use in a subsequent version of the model in order to save runtime.

On the Request tab, in the Output control group, click the  Data structures (PS) icon.

Figure 1. The PS - Control data structure dialog.

It is important to be familiar with the solution process of the MoM to understand this card. The solution of electromagnetic problems based on the MoM involves a setting up a system of linear equations, which by default is solved using an LU-decomposition and a subsequent backwards substitution. This card can be used to save the matrix of the system of linear equations, its LU decomposition, or the solution vector (which also includes PO currents and so forth). Such elements can also be loaded again.

This card can also be used to save the cable per-unit-length parameters between frequency runs to prevent the parameter recalculation for every frequency.


Save / read matrix elements
Select this option to save or read the matrix elements of the system of linear equations. This is typically not recommended, since the file will be large and the time to recompute the matrix elements is typically much shorter than the time for the LU-decomposition of the matrix.
Save / read LU decomposed matrix
Select this option to save or read the LU-decomposition of the system of linear equations. This option is useful if you want to solve a problem repeatedly with multiple different excitations (right-hand sides). Note that if you do this in one Feko run (that is one .pre file), then Feko keeps the LU-decomposition automatically in memory.
Save / read currents
Select this option to save or read the solution vector of the system of linear equations. The solution vector corresponds to the currents on the structure being simulated.
Save / read cable per-unit-length parameters
Select this option to save or read the cable per-unit-length parameters.

Feko always uses the most efficient computation when doing multiple solutions in one file. However, sometimes one might also do a solution, look at the results and then change certain parameters. Then the option to store the solution in the .str file and load it again or the similar option for the LU-decomposition are particularly useful. The option to save the currents is applicable when the solution remains unchanged (such as the geometry, material parameters, loads, frequency and sources), but when one wants to compute the near- or far fields with different options. The storage of the LU-decomposition is useful when only the right-hand side of the system of linear equations changes (for example the direction of incidence of a plane wave). Feko has built-in checks and reports a warning if, for example, currents were exported for one frequency and are later imported again for another frequency.

Note that the .str file can be used for MoM, MLFMM, PO, and FEM, while the .mat and .lud files are only applicable when the standard MoM is used. The .mat file can only be stored/read for sequential in-core solutions.

Note that models built with PREFEKO on different computers may not be identical due to very small rounding differences of different CPUs. It is therefore advisable to run PREFEKO only on one computer when using this card, to ensure consistency in the .fek files. The .fek files can then be copied to another computer if required. (For example, a user may calculate and store the current distribution for a large model on a fast workstation and later load this to calculate different near fields on a small PC. To ensure that the current solution is valid on the PC, the original .fek file should be generated on the PC and copied to the workstation.)

If the PS card is used to specify that data should be read from a file, the PS card may occur only once in the input file.

Tip: Place the PS card right after the EG card.