contrib/perf-utils/subsetmaker.py

stabletailgraph: clarify naiveness of current implementation

Both the naive and the actual versions of the algorithms are going to co-exist
for the tests. This makes is clearer that this one is naive.

"""revset to select sample of repository

Hopefully this is useful to create interesting discovery cases.
"""

import collections
import random

from mercurial.i18n import _

from mercurial import (
    registrar,
    revset,
    revsetlang,
    smartset,
)

import sortedcontainers

SortedSet = sortedcontainers.SortedSet

revsetpredicate = registrar.revsetpredicate()


@revsetpredicate(b'subsetspec("<spec>")')
def subsetmarkerspec(repo, subset, x):
    """use a shorthand spec as used by search-discovery-case

    Supported format are:

    - "scratch-count-seed": not scratch(all(), count, "seed")
    - "randomantichain-seed": ::randomantichain(all(), "seed")
    - "rev-REV": "::REV"
    """
    args = revsetlang.getargs(
        x, 0, 1, _(b'subsetspec("spec") required an argument')
    )

    spec = revsetlang.getstring(args[0], _(b"spec should be a string"))
    case = spec.split(b'-')
    t = case[0]
    if t == b'scratch':
        spec_revset = b'not scratch(all(), %s, "%s")' % (case[1], case[2])
    elif t == b'randomantichain':
        spec_revset = b'::randomantichain(all(), "%s")' % case[1]
    elif t == b'rev':
        spec_revset = b'::%d' % case[1]
    else:
        assert False, spec

    selected = repo.revs(spec_revset)

    return selected & subset


@revsetpredicate(b'scratch(REVS, <count>, [seed])')
def scratch(repo, subset, x):
    """randomly remove <count> revision from the repository top

    This subset is created by recursively picking changeset starting from the
    heads. It can be summarized using the following algorithm::

        selected = set()
        for i in range(<count>):
            unselected = repo.revs("not <selected>")
            candidates = repo.revs("heads(<unselected>)")
            pick = random.choice(candidates)
            selected.add(pick)
    """
    m = _(b"scratch expects revisions, count argument and an optional seed")
    args = revsetlang.getargs(x, 2, 3, m)
    if len(args) == 2:
        x, n = args
        rand = random
    elif len(args) == 3:
        x, n, seed = args
        seed = revsetlang.getinteger(seed, _(b"seed should be a number"))
        rand = random.Random(seed)
    else:
        assert False

    n = revsetlang.getinteger(n, _(b"scratch expects a number"))

    selected = set()
    heads = SortedSet()
    children_count = collections.defaultdict(lambda: 0)
    parents = repo.changelog._uncheckedparentrevs

    baseset = revset.getset(repo, smartset.fullreposet(repo), x)
    baseset.sort()
    for r in baseset:
        heads.add(r)

        p1, p2 = parents(r)
        if p1 >= 0:
            heads.discard(p1)
            children_count[p1] += 1
        if p2 >= 0:
            heads.discard(p2)
            children_count[p2] += 1

    for h in heads:
        assert children_count[h] == 0

    selected = set()
    for x in range(n):
        if not heads:
            break
        pick = rand.choice(heads)
        heads.remove(pick)
        assert pick not in selected
        selected.add(pick)
        p1, p2 = parents(pick)
        if p1 in children_count:
            assert p1 in children_count
            children_count[p1] -= 1
            assert children_count[p1] >= 0
            if children_count[p1] == 0:
                assert p1 not in selected, (r, p1)
                heads.add(p1)
        if p2 in children_count:
            assert p2 in children_count
            children_count[p2] -= 1
            assert children_count[p2] >= 0
            if children_count[p2] == 0:
                assert p2 not in selected, (r, p2)
                heads.add(p2)

    return smartset.baseset(selected) & subset


@revsetpredicate(b'randomantichain(REVS, [seed])')
def antichain(repo, subset, x):
    """Pick a random anti-chain in the repository

    A antichain is a set of changeset where there isn't any element that is
    either a descendant or ancestors of any other element in the set. In other
    word, all the elements are independant. It can be summarized with the
    following algorithm::

    selected = set()
    unselected = repo.revs('all()')
    while unselected:
        pick = random.choice(unselected)
        selected.add(pick)
        unselected -= repo.revs('::<pick> + <pick>::')
    """

    args = revsetlang.getargs(
        x, 1, 2, _(b"randomantichain expects revisions and an optional seed")
    )
    if len(args) == 1:
        (x,) = args
        rand = random
    elif len(args) == 2:
        x, seed = args
        seed = revsetlang.getinteger(seed, _(b"seed should be a number"))
        rand = random.Random(seed)
    else:
        assert False

    cl = repo.changelog

    # We already have cheap access to the parent mapping.
    # However, we need to build a mapping of the children mapping
    parents = repo.changelog._uncheckedparentrevs
    children_map = collections.defaultdict(list)
    for r in cl:
        p1, p2 = parents(r)
        if p1 >= 0:
            children_map[p1].append(r)
        if p2 >= 0:
            children_map[p2].append(r)
    children = children_map.__getitem__

    selected = set()
    undecided = SortedSet(cl)

    while undecided:
        # while there is "undecided content", we pick a random changeset X
        # and we remove anything in `::X + X::` from undecided content
        pick = rand.choice(undecided)
        selected.add(pick)
        undecided.remove(pick)

        ancestors = set(p for p in parents(pick) if p in undecided)
        descendants = set(c for c in children(pick) if c in undecided)

        while ancestors:
            current = ancestors.pop()
            undecided.remove(current)
            for p in parents(current):
                if p in undecided:
                    ancestors.add(p)
        while descendants:
            current = descendants.pop()
            undecided.remove(current)
            for p in children(current):
                if p in undecided:
                    ancestors.add(p)

    return smartset.baseset(selected) & subset