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#!/usr/bin/env python
#
# Simple program to compute the biggest twin prime pair less than each
# power of 2.
#
# This is used to choose "good" sizes for the hashtable.
#
# Using a prime for "num_slot" is useful as that guarantees that the
# orbit touches every slot (which is useful to have a good
# implementation of open addressing, because this means that as long
# as you have free slots, you can add elements, no matter what their
# hash is).
#
# Using a prime for the linear offset is not actually needed, but
# avoiding composite numbers is usually a good idea, because they tend
# to show bad behavior depending on the patterns found in the input
# data.
#
def isprime(x):
d = 2
while d * d <= x:
if x % d == 0:
return False
d = d + 1
return True
for i in range(3, 33):
x = 2 ** i
while not (isprime(x) and isprime(x-2)):
x = x - 1
print " %d," % x
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