Fix rerate logic (DMOJ)

judge/admin/contest.py

@@ -282,7 +282,7 @@ class ContestParticipationForm(ModelForm):
 
 class ContestParticipationAdmin(admin.ModelAdmin):
     fields = ('contest', 'user', 'real_start', 'virtual', 'is_disqualified')
-    list_display = ('contest', 'username', 'show_virtual', 'real_start', 'score', 'cumtime')
+    list_display = ('contest', 'username', 'show_virtual', 'real_start', 'score', 'cumtime', 'tiebreaker')
     actions = ['recalculate_results']
     actions_on_bottom = actions_on_top = True
     search_fields = ('contest__key', 'contest__name', 'user__user__username')
@@ -292,7 +292,7 @@ class ContestParticipationAdmin(admin.ModelAdmin):
     def get_queryset(self, request):
         return super(ContestParticipationAdmin, self).get_queryset(request).only(
             'contest__name', 'contest__format_name', 'contest__format_config',
-            'user__user__username', 'real_start', 'score', 'cumtime', 'virtual',
+            'user__user__username', 'real_start', 'score', 'cumtime', 'tiebreaker', 'virtual',
         )
 
     def save_model(self, request, obj, form, change):

judge/contest_format/__init__.py

@@ -1,5 +1,6 @@
 from judge.contest_format.atcoder import AtCoderContestFormat
 from judge.contest_format.default import DefaultContestFormat
 from judge.contest_format.ecoo import ECOOContestFormat
+from judge.contest_format.icpc import ICPCContestFormat
 from judge.contest_format.ioi import IOIContestFormat
 from judge.contest_format.registry import choices, formats

judge/contest_format/atcoder.py

@@ -91,6 +91,7 @@ class AtCoderContestFormat(DefaultContestFormat):
 
         participation.cumtime = cumtime + penalty
         participation.score = points
+        participation.tiebreaker = 0
         participation.format_data = format_data
         participation.save()
 

judge/contest_format/default.py

@@ -41,6 +41,7 @@ class DefaultContestFormat(BaseContestFormat):
 
         participation.cumtime = max(cumtime, 0)
         participation.score = points
+        participation.tiebreaker = 0
         participation.format_data = format_data
         participation.save()
 

judge/contest_format/ecoo.py

@@ -92,6 +92,7 @@ class ECOOContestFormat(DefaultContestFormat):
 
         participation.cumtime = cumtime
         participation.score = points
+        participation.tiebreaker = 0
         participation.format_data = format_data
         participation.save()
 

judge/contest_format/ioi.py

@@ -73,6 +73,7 @@ class IOIContestFormat(DefaultContestFormat):
 
         participation.cumtime = max(cumtime, 0)
         participation.score = points
+        participation.tiebreaker = 0
         participation.format_data = format_data
         participation.save()
 

judge/ratings.py

@@ -1,12 +1,31 @@
 import math
 from bisect import bisect
-from operator import itemgetter
+from operator import attrgetter, itemgetter
 
 from django.db import connection, transaction
-from django.db.models import Count
+from django.db.models import Count, OuterRef, Subquery
+from django.db.models.functions import Coalesce
 from django.utils import timezone
 
-from judge.utils.ranker import tie_ranker
+
+def tie_ranker(iterable, key=attrgetter('points')):
+    rank = 0
+    delta = 1
+    last = None
+    buf = []
+    for item in iterable:
+        new = key(item)
+        if new != last:
+            for _ in buf:
+                yield rank + (delta - 1) / 2.0
+            rank += delta
+            delta = 0
+            buf = []
+        delta += 1
+        buf.append(item)
+        last = key(item)
+    for _ in buf:
+        yield rank + (delta - 1) / 2.0
 
 
 def rational_approximation(t):
@@ -35,7 +54,7 @@ def WP(RA, RB, VA, VB):
     return (math.erf((RB - RA) / math.sqrt(2 * (VA * VA + VB * VB))) + 1) / 2.0
 
 
-def recalculate_ratings(old_rating, old_volatility, actual_rank, times_rated):
+def recalculate_ratings(old_rating, old_volatility, actual_rank, times_rated, is_disqualified):
     # actual_rank: 1 is first place, N is last place
     # if there are ties, use the average of places (if places 2, 3, 4, 5 tie, use 3.5 for all of them)
 
@@ -76,6 +95,12 @@ def recalculate_ratings(old_rating, old_volatility, actual_rank, times_rated):
         else:
             new_volatility[i] = math.sqrt(((new_rating[i] - old_rating[i]) ** 2) / Weight +
                                           (old_volatility[i] ** 2) / (Weight + 1))
+
+        if is_disqualified[i]:
+            # DQed users can manipulate TopCoder ratings to get higher volatility in order to increase their rating
+            # later on, prohibit this by ensuring their volatility never increases in this situation
+            new_volatility[i] = min(new_volatility[i], old_volatility[i])
+
         if abs(old_rating[i] - new_rating[i]) > Cap:
             if old_rating[i] < new_rating[i]:
                 new_rating[i] = old_rating[i] + Cap
@@ -96,49 +121,37 @@ def recalculate_ratings(old_rating, old_volatility, actual_rank, times_rated):
 def rate_contest(contest):
     from judge.models import Rating, Profile
 
-    cursor = connection.cursor()
-    cursor.execute('''
-        SELECT judge_rating.user_id, judge_rating.rating, judge_rating.volatility, r.times
-        FROM judge_rating INNER JOIN
-             judge_contest ON (judge_contest.id = judge_rating.contest_id) INNER JOIN (
-            SELECT judge_rating.user_id AS id, MAX(judge_contest.end_time) AS last_time,
-                   COUNT(judge_rating.user_id) AS times
-            FROM judge_contestparticipation INNER JOIN
-                 judge_rating ON (judge_rating.user_id = judge_contestparticipation.user_id) INNER JOIN
-                 judge_contest ON (judge_contest.id = judge_rating.contest_id)
-            WHERE judge_contestparticipation.contest_id = %s AND judge_contest.end_time < %s AND
-                  judge_contestparticipation.user_id NOT IN (
-                      SELECT profile_id FROM judge_contest_rate_exclude WHERE contest_id = %s
-                  ) AND judge_contestparticipation.virtual = 0
-            GROUP BY judge_rating.user_id
-            ORDER BY judge_contestparticipation.score DESC, judge_contestparticipation.cumtime ASC
-        ) AS r ON (judge_rating.user_id = r.id AND judge_contest.end_time = r.last_time)
-    ''', (contest.id, contest.end_time, contest.id))
-    data = {user: (rating, volatility, times) for user, rating, volatility, times in cursor.fetchall()}
-    cursor.close()
-
-    users = contest.users.order_by('is_disqualified', '-score', 'cumtime').annotate(submissions=Count('submission')) \
-                   .exclude(user_id__in=contest.rate_exclude.all()).filter(virtual=0, user__is_unlisted=False) \
-                   .values_list('id', 'user_id', 'score', 'cumtime')
+    rating_subquery = Rating.objects.filter(user=OuterRef('user'))
+    rating_sorted = rating_subquery.order_by('-contest__end_time')
+    users = contest.users.order_by('is_disqualified', '-score', 'cumtime', 'tiebreaker') \
+        .annotate(submissions=Count('submission'),
+                  last_rating=Coalesce(Subquery(rating_sorted.values('rating')[:1]), 1200),
+                  volatility=Coalesce(Subquery(rating_sorted.values('volatility')[:1]), 535),
+                  times=Coalesce(Subquery(rating_subquery.order_by().values('user_id')
+                                          .annotate(count=Count('id')).values('count')), 0)) \
+        .exclude(user_id__in=contest.rate_exclude.all()) \
+        .filter(virtual=0).values('id', 'user_id', 'score', 'cumtime', 'tiebreaker', 'is_disqualified',
+                                  'last_rating', 'volatility', 'times')
     if not contest.rate_all:
         users = users.filter(submissions__gt=0)
     if contest.rating_floor is not None:
-        users = users.exclude(user__rating__lt=contest.rating_floor)
+        users = users.exclude(last_rating__lt=contest.rating_floor)
     if contest.rating_ceiling is not None:
-        users = users.exclude(user__rating__gt=contest.rating_ceiling)
-    users = list(tie_ranker(users, key=itemgetter(2, 3)))
-    participation_ids = [user[1][0] for user in users]
-    user_ids = [user[1][1] for user in users]
-    ranking = list(map(itemgetter(0), users))
-    old_data = [data.get(user, (1200, 535, 0)) for user in user_ids]
-    old_rating = list(map(itemgetter(0), old_data))
-    old_volatility = list(map(itemgetter(1), old_data))
-    times_ranked = list(map(itemgetter(2), old_data))
-    rating, volatility = recalculate_ratings(old_rating, old_volatility, ranking, times_ranked)
+        users = users.exclude(last_rating__gt=contest.rating_ceiling)
+
+    users = list(users)
+    participation_ids = list(map(itemgetter('id'), users))
+    user_ids = list(map(itemgetter('user_id'), users))
+    is_disqualified = list(map(itemgetter('is_disqualified'), users))
+    ranking = list(tie_ranker(users, key=itemgetter('score', 'cumtime', 'tiebreaker')))
+    old_rating = list(map(itemgetter('last_rating'), users))
+    old_volatility = list(map(itemgetter('volatility'), users))
+    times_ranked = list(map(itemgetter('times'), users))
+    rating, volatility = recalculate_ratings(old_rating, old_volatility, ranking, times_ranked, is_disqualified)
 
     now = timezone.now()
-    ratings = [Rating(user_id=id, contest=contest, rating=r, volatility=v, last_rated=now, participation_id=p, rank=z)
-               for id, p, r, v, z in zip(user_ids, participation_ids, rating, volatility, ranking)]
+    ratings = [Rating(user_id=i, contest=contest, rating=r, volatility=v, last_rated=now, participation_id=p, rank=z)
+               for i, p, r, v, z in zip(user_ids, participation_ids, rating, volatility, ranking)]
     cursor = connection.cursor()
     cursor.execute('CREATE TEMPORARY TABLE _profile_rating_update(id integer, rating integer)')
     cursor.executemany('INSERT INTO _profile_rating_update VALUES (%s, %s)', list(zip(user_ids, rating)))
@@ -178,4 +191,4 @@ def rating_progress(rating):
         return 1.0
     prev = 0 if not level else RATING_VALUES[level - 1]
     next = RATING_VALUES[level]
-    return (rating - prev + 0.0) / (next - prev)
+    return (rating - prev + 0.0) / (next - prev)

judge/utils/ranker.py

@@ -13,22 +13,3 @@ def ranker(iterable, key=attrgetter('points'), rank=0):
         yield rank, item
         last = key(item)
 
-
-def tie_ranker(iterable, key=attrgetter('points')):
-    rank = 0
-    delta = 1
-    last = None
-    buf = []
-    for item in iterable:
-        new = key(item)
-        if new != last:
-            for i in buf:
-                yield rank + (delta - 1) / 2.0, i
-            rank += delta
-            delta = 0
-            buf = []
-        delta += 1
-        buf.append(item)
-        last = key(item)
-    for i in buf:
-        yield rank + (delta - 1) / 2.0, i

judge/views/api/api_v1.py

@@ -35,7 +35,7 @@ def api_v1_contest_detail(request, contest):
     can_see_rankings = contest.can_see_full_scoreboard(request.user)
     problems = list(contest.contest_problems.select_related('problem')
                     .defer('problem__description').order_by('order'))
-    participations = (contest.users.filter(virtual=0, user__is_unlisted=False)
+    participations = (contest.users.filter(virtual=0)
                       .prefetch_related('user__organizations')
                       .annotate(username=F('user__user__username'))
                       .order_by('-score', 'cumtime') if can_see_rankings else [])
@@ -134,16 +134,15 @@ def api_v1_user_info(request, user):
     last_rating = profile.ratings.last()
 
     contest_history = {}
-    if not profile.is_unlisted:
-        participations = ContestParticipation.objects.filter(user=profile, virtual=0, contest__is_visible=True,
-                                                             contest__is_private=False,
-                                                             contest__is_organization_private=False)
-        for contest_key, rating, volatility in participations.values_list('contest__key', 'rating__rating',
-                                                                          'rating__volatility'):
-            contest_history[contest_key] = {
-                'rating': rating,
-                'volatility': volatility,
-            }
+    participations = ContestParticipation.objects.filter(user=profile, virtual=0, contest__is_visible=True,
+                                                         contest__is_private=False,
+                                                         contest__is_organization_private=False)
+    for contest_key, rating, volatility in participations.values_list('contest__key', 'rating__rating',
+                                                                      'rating__volatility'):
+        contest_history[contest_key] = {
+            'rating': rating,
+            'volatility': volatility,
+        }
 
     resp['contests'] = {
         'current_rating': last_rating.rating if last_rating else None,

judge/views/contests.py

@@ -591,7 +591,7 @@ class ContestStats(TitleMixin, ContestMixin, DetailView):
 
 ContestRankingProfile = namedtuple(
     'ContestRankingProfile',
-    'id user css_class username points cumtime organization participation '
+    'id user css_class username points cumtime tiebreaker organization participation '
     'participation_rating problem_cells result_cell',
 )
 
@@ -607,6 +607,7 @@ def make_contest_ranking_profile(contest, participation, contest_problems):
         username=user.username,
         points=participation.score,
         cumtime=participation.cumtime,
+        tiebreaker=participation.tiebreaker,
         organization=user.organization,
         participation_rating=participation.rating.rating if hasattr(participation, 'rating') else None,
         problem_cells=[contest.format.display_user_problem(participation, contest_problem)
@@ -622,17 +623,17 @@ def base_contest_ranking_list(contest, problems, queryset):
 
 
 def contest_ranking_list(contest, problems):
-    return base_contest_ranking_list(contest, problems, contest.users.filter(virtual=0, user__is_unlisted=False)
+    return base_contest_ranking_list(contest, problems, contest.users.filter(virtual=0)
                                      .prefetch_related('user__organizations')
                                      .extra(select={'round_score': 'round(score, 6)'})
-                                     .order_by('is_disqualified', '-round_score', 'cumtime'))
+                                     .order_by('is_disqualified', '-round_score', 'cumtime', 'tiebreaker'))
 
 
 def get_contest_ranking_list(request, contest, participation=None, ranking_list=contest_ranking_list,
                              show_current_virtual=True, ranker=ranker):
     problems = list(contest.contest_problems.select_related('problem').defer('problem__description').order_by('order'))
 
-    users = ranker(ranking_list(contest, problems), key=attrgetter('points', 'cumtime'))
+    users = ranker(ranking_list(contest, problems), key=attrgetter('points', 'cumtime', 'tiebreaker'))
     
     if show_current_virtual:
         if participation is None and request.user.is_authenticated: