Might be of interest to some that there is now a GPLv3 code for
generating finite lattices. Paper is at
https://arxiv.org/pdf/1609.08255.pdf
code can be downloaded from
https://bitbucket.org/vgebhardt/unlabelled-lattices/downloads/
and it can be used for example like
from sage.combinat.posets.lattices import FiniteLatticePoset
from sage.categories.finite_lattice_posets import FiniteLatticePosets
import subprocess
def generate_lattices(n): # Add check for the argument etc.
cmd=["/SOME/PATH/vgebhardt-unlabelled-lattices-367022714ef8/UnlabelledLattices"]
args=[str(n)]
sp=subprocess.Popen(cmd+args, shell=False, stdin=subprocess.PIPE,
stdout=subprocess.PIPE, stderr=subprocess.PIPE, close_fds=True)
reader=iter(lambda: sp.stdout.read(n*(n-1)/2+1), '')
while True:
S=reader.next()[:-1]
yield FiniteLatticePoset(DiGraph([range(n), lambda a, b: a < b and
S[b*(b-1)/2+a]=='1']), category=FiniteLatticePosets())
I think someone, like me, should make an optional package from this.
--
Jori Mäntysalo
