| System Identification Toolbox | |
Memory/Speed Trade-Offs
On machines with no formal memory limitations, it is still of interest to monitor the sizes of the matrices that are formed. The typical situation is when an overdetermined set of linear equations is solved for the least squares solution. The solution time depends, of course, on the dimensions of the corresponding matrix. The number of rows corresponds to the number of observed data, while the number of columns corresponds to the number of estimated parameters. The property MaxSize used with all the relevant M-files, guarantees that no matrix with more than MaxSize elements is formed. Larger data sets and/or higher order models are handled by for loops. for loops give linear increase in time when the data record is increased, plus some overhead.
If you regularly work with large data sets and/or high order models, it is advisable to tailor the memory and speed trade-off to your machine by choosing MaxSize carefully. You could also change the default value of MaxSize in the M-file idmsize. Then the default value of MaxSize (that is 'Auto') will be tailored to your needs. Note that this value is allowed to depend on the number of rows and columns of the matrices formed.
| | Connections Between the Control System Toolbox and the System Identification Toolbox | Local Minima | |