The necessary condition is found to be degeneracy at the presence of more than one leaving variable is essential for multiple optimal solutions. But what is the sufficient condition?
Is $C-C_b*inv(B)*A=0$ is sufficient one?
Also if one has one optimal solution along with the in formation about basic and nonbasic elements, is there any method to obtain all optimal solutions (the vertex solutions).
http://www-personal.umich.edu/~murty/segments.pdf
– Parikshit Aug 13 '17 at 13:23