Description

The incremental fixed lag smoother creates an iSAM instance, but does not set the findUnusedFactorSlots flag to true, even though the docs in iSAM2Params.h say: "When you will be removing many factors, e.g. when using ISAM2 as a fixed-lag smoother, enable this option to add factors in the first available factor slots, to avoid accumulating NULL factor slots, at the cost of having to search for slots every time a factor is added."

Steps to reproduce

just run incremental fixed lag smoother and you will see number of factors grow...

Expected behavior

Should be approx constant.

Proposed fix

Change construction of iSAM2 instance in incremental fixed lag smoother...