Complex sentence: Initially, Klee and Minty showed that the simplex algorithm was not a polynomial-time algorithm when applied to their cube, and modifications of it showed poor behavior for other basis-exchange pivoting algorithms and also for interior-point algorithms.
Split into simpler sentences: Initially, Klee and Minty showed that the simplex algorithm was not a polynomial-time algorithm when applied to their cube. Minty cube have shown poor behavior both for other basis-exchange pivoting algorithms and also for interior-point algorithms.