=== Stress test: how often is the greedy 0-1 answer wrong? ===
  n =   5: greedy was suboptimal in   4241 of 20000 random instances (21.2%),  mean value/optimum = 0.9789,  worst = 0.4577
  n =  10: greedy was suboptimal in   7033 of 20000 random instances (35.2%),  mean value/optimum = 0.9868,  worst = 0.7821
  n =  20: greedy was suboptimal in   9666 of 20000 random instances (48.3%),  mean value/optimum = 0.9930,  worst = 0.9250

=== Fractional greedy is never wrong: same stress test ===
  n =   5: fractional greedy fell below the 0-1 optimum in 0 of 20000 instances
  n =  10: fractional greedy fell below the 0-1 optimum in 0 of 20000 instances
  n =  20: fractional greedy fell below the 0-1 optimum in 0 of 20000 instances
