This PR introduces a classification of variables that are simultaneously basic and located on their lower/upper bounds. These variables are called meta-stable. They are considered stable for means of computing the Newton direction. However, sensitivity derivatives associated with these meta-stable basic variables are zero out. This is needed because these variables are at the limit of stability and these derivatives are thus not defined at the bounds.
This PR introduces a classification of variables that are simultaneously basic and located on their lower/upper bounds. These variables are called meta-stable. They are considered stable for means of computing the Newton direction. However, sensitivity derivatives associated with these meta-stable basic variables are zero out. This is needed because these variables are at the limit of stability and these derivatives are thus not defined at the bounds.