random_seed_simulation.rb

ULONG_MAX = 4294967295

zones = (1..5).to_a

times = [1212, 1213, 1214, 1215,
         1312, 1313, 1314, 1315,
         1412, 1413, 1414, 1415,
         1512, 1513, 1514, 1515]
purposes = (1001..1060).to_a
num_cars = [0,1,2,3]

seeds = zones.flat_map { |z| 
          times.flat_map { |t| 
            purposes.flat_map { |purp| 
              num_cars.map { |nc| 
                (42 * z * ("%4d%4d%1d" % [t,purp,nc]).to_i) % ULONG_MAX
              }
            }
          }
}


a,b = [seeds.uniq.size, seeds.size]
p [a,b,a.to_f/b]

# It appears that 500 zones is enough to get a feel for the collisions
# z = 1..5 => [19200, 19200, 1.0]
# z = 1..500 => [1918490, 1920000, 0.9992135416666666]
# z = 1..5000 => [19035347, 19200000, 0.9914243229166667]