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scoring.py

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+# tag::scoring_imports[]
+from __future__ import absolute_import
+from collections import namedtuple
+
+from tugo.gotypes import Player, Point
+# end::scoring_imports[]
+
+
+# tag::scoring_territory[]
+class Territory:
+    def __init__(self, territory_map):  # <1>
+        self.num_black_territory = 0
+        self.num_white_territory = 0
+        self.num_black_stones = 0
+        self.num_white_stones = 0
+        self.num_dame = 0
+        self.dame_points = []
+        for point, status in territory_map.items():  # <2>
+            if status == Player.black:
+                self.num_black_stones += 1
+            elif status == Player.white:
+                self.num_white_stones += 1
+            elif status == 'territory_b':
+                self.num_black_territory += 1
+            elif status == 'territory_w':
+                self.num_white_territory += 1
+            elif status == 'dame':
+                self.num_dame += 1
+                self.dame_points.append(point)
+
+# <1> A `territory_map` splits the board into stones, territory and neutral points (dame).
+# <2> Depending on the status of a point, we increment the respective counter.
+# end::scoring_territory[]
+
+
+# tag::scoring_game_result[]
+class GameResult(namedtuple('GameResult', 'b w komi')):
+    @property
+    def winner(self):
+        if self.b > self.w + self.komi:
+            return Player.black
+        return Player.white
+
+    @property
+    def winning_margin(self):
+        w = self.w + self.komi
+        return abs(self.b - w)
+
+    def __str__(self):
+        w = self.w + self.komi
+        if self.b > w:
+            return 'B+%.1f' % (self.b - w,)
+        return 'W+%.1f' % (w - self.b,)
+# end::scoring_game_result[]
+
+
+""" evaluate_territory:
+Map a board into territory and dame.
+
+Any points that are completely surrounded by a single color are
+counted as territory; it makes no attempt to identify even
+trivially dead groups.
+"""
+
+
+# tag::scoring_evaluate_territory[]
+def evaluate_territory(board):
+
+    status = {}
+    for r in range(1, board.num_rows + 1):
+        for c in range(1, board.num_cols + 1):
+            p = Point(row=r, col=c)
+            if p in status:  # <1>
+                continue
+            stone = board.get(p)
+            if stone is not None:  # <2>
+                status[p] = board.get(p)
+            else:
+                group, neighbors = _collect_region(p, board)
+                if len(neighbors) == 1:  # <3>
+                    neighbor_stone = neighbors.pop()
+                    stone_str = 'b' if neighbor_stone == Player.black else 'w'
+                    fill_with = 'territory_' + stone_str
+                else:
+                    fill_with = 'dame'  # <4>
+                for pos in group:
+                    status[pos] = fill_with
+    return Territory(status)
+
+# <1> Skip the point, if you already visited this as part of a different group.
+# <2> If the point is a stone, add it as status.
+# <3> If a point is completely surrounded by black or white stones, count it as territory.
+# <4> Otherwise the point has to be a neutral point, so we add it to dame.
+# end::scoring_evaluate_territory[]
+
+
+""" _collect_region:
+
+Find the contiguous section of a board containing a point. Also
+identify all the boundary points.
+"""
+
+
+# tag::scoring_collect_region[]
+def _collect_region(start_pos, board, visited=None):
+
+    if visited is None:
+        visited = {}
+    if start_pos in visited:
+        return [], set()
+    all_points = [start_pos]
+    all_borders = set()
+    visited[start_pos] = True
+    here = board.get(start_pos)
+    deltas = [(-1, 0), (1, 0), (0, -1), (0, 1)]
+    for delta_r, delta_c in deltas:
+        next_p = Point(row=start_pos.row + delta_r, col=start_pos.col + delta_c)
+        if not board.is_on_grid(next_p):
+            continue
+        neighbor = board.get(next_p)
+        if neighbor == here:
+            points, borders = _collect_region(next_p, board, visited)
+            all_points += points
+            all_borders |= borders
+        else:
+            all_borders.add(neighbor)
+    return all_points, all_borders
+# end::scoring_collect_region[]
+
+
+# tag::scoring_compute_game_result[]
+def compute_game_result(game_state):
+    territory = evaluate_territory(game_state.board)
+    return GameResult(
+        territory.num_black_territory + territory.num_black_stones,
+        territory.num_white_territory + territory.num_white_stones,
+        komi=7.5)
+# end::scoring_compute_game_result[]