rhos(
tau) = (1/
np)
size{
p in
P :
rp,s <=
tau}
is the probability that a performance ratio rp,s
is within a factor tau of the best possible ratio. For instance,
for tau = 2, rhos(tau) says how often can
solver s get results in a time not worse that two-times the time
of the best solver. Also, the higher rhos, the higher
is the probability that solver s can solve all problems from P.