95 

    96 

    97 @revsetpredicate(b'randomantichain(REVS, [seed])')

    98 def antichain(repo, subset, x):

    99     """Pick a random anti-chain in the repository

   100 

   101     A antichain is a set of changeset where there isn't any element that is

   102     either a descendant or ancestors of any other element in the set. In other

   103     word, all the elements are independant. It can be summarized with the

   104     following algorithm::

   105 

   106     selected = set()

   107     unselected = repo.revs('all()')

   108     while unselected:

   109         pick = random.choice(unselected)

   110         selected.add(pick)

   111         unselected -= repo.revs('::<pick> + <pick>::')

   112     """

   113 

   114     args = revsetlang.getargs(

   115         x, 1, 2, _(b"randomantichain expects revisions and an optional seed")

   116     )

   117     if len(args) == 1:

   118         (x,) = args

   119         rand = random

   120     elif len(args) == 2:

   121         x, seed = args

   122         seed = revsetlang.getinteger(seed, _(b"seed should be a number"))

   123         rand = random.Random(seed)

   124     else:

   125         assert False

   126 

   127     selected = set()

   128 

   129     baseset = revset.getset(repo, smartset.fullreposet(repo), x)

   130     undecided = baseset

   131 

   132     while undecided:

   133         pick = rand.choice(list(undecided))

   134         selected.add(pick)

   135         undecided = repo.revs(

   136             '%ld and not (::%ld or %ld::head())', baseset, selected, selected

   137         )

   138 

   139     return smartset.baseset(selected) & subset