#17048: Faster Posets.RandomPoset
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Reporter: jmantysalo | Owner:
Type: enhancement | Status: new
Priority: minor | Milestone: sage-wishlist
Component: combinatorics | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Comment (by jmantysalo):
Maybe we could also generate random posets with given restrictions? For
example
{{{
# Graded poset
# set_random_seed(0)
from sage.misc.prandom import random
from sage.misc.randstate import current_randstate
dice=current_randstate()
n=20
prob=0.2
# Too many 1-element levels... make better.
levels=Partitions(n).random_element()
p=Permutations(len(levels)).random_element()
levels=[levels[x-1] for x in p]
# Poset P will have 0..levels[0] as minimal element,
# levels[0]..levels[1]-1 covering them and so on.
G=DiGraph({x:[] for x in range(0,n)})
prev_start=0
prev_end=levels[0]
for i in levels[1:]:
# Connect every element of previous level to some element on this
level
for prev in range(prev_start, prev_end):
r=randint(prev_end, prev_end+i-1)
G.add_edge(prev, r)
# Connect every element of this level to some element on previous
level
for e in range(prev_end, prev_end+i):
if G.in_degree(e) == 0:
r=randint(prev_start, prev_end-1)
G.add_edge(r, e)
# And now the random part
for e1 in range(prev_start, prev_end):
for e2 in range(prev_end, prev_end+i):
if dice.c_rand_double() < prob:
G.add_edge(e1, e2)
prev_start=prev_end
prev_end=prev_end+i
P=Poset(G);
}}}
Calling this kind of functions could be something like
`Posets.RandomPoset(20, 0.2, properties=['graded', 'connected',
'third_property'])`.
--
Ticket URL: <http://trac.sagemath.org/ticket/17048#comment:1>
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