45th Annual IEEE Symposium on Foundations of Computer Science (FOCS'04)
Random Edge Can Be Exponential on Abstract Cubes
Rome, Italy
October 17-October 19
ISBN: 0-7695-2228-9
We prove that RANDOM EDGE, the simplex algorithm that always chooses a random improving edge to proceed on, can take a mildly exponential number of steps in the model of abstract objective functions (introduced by Wiliamson Hoke [27] and by Kalai [16] under different names). We define an abstract objective function on the n-dimensional cube for which the algorithm, started at a random vertex, needs at least exp(const ? n^1/3) steps with high probability. The best previous lower bound was quadratic. So in order for RANDOM EDGE to succeed in polynomial time, geometry must help.