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// Copyright 2018 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "cc/position.h"
#include <sstream>
#include <utility>
#include "absl/strings/str_format.h"
#include "cc/tiny_set.h"
namespace minigo {
namespace {
constexpr char kPrintWhite[] = "\x1b[0;31;47m";
constexpr char kPrintBlack[] = "\x1b[0;31;40m";
constexpr char kPrintEmpty[] = "\x1b[0;31;43m";
constexpr char kPrintNormal[] = "\x1b[0m";
} // namespace
const std::array<inline_vector<Coord, 4>, kN* kN> kNeighborCoords = []() {
std::array<inline_vector<Coord, 4>, kN * kN> result;
for (int row = 0; row < kN; ++row) {
for (int col = 0; col < kN; ++col) {
auto& coords = result[row * kN + col];
if (col > 0) {
coords.emplace_back(row, col - 1);
}
if (col < kN - 1) {
coords.emplace_back(row, col + 1);
}
if (row > 0) {
coords.emplace_back(row - 1, col);
}
if (row < kN - 1) {
coords.emplace_back(row + 1, col);
}
}
}
return result;
}();
Position::Position(BoardVisitor* bv, GroupVisitor* gv, Color to_play, int n)
: board_visitor_(bv),
group_visitor_(gv),
to_play_(to_play),
n_(n),
stone_hash_(0) {}
Position::Position(BoardVisitor* bv, GroupVisitor* gv, const Position& position)
: Position(position) {
board_visitor_ = bv;
group_visitor_ = gv;
}
void Position::PlayMove(Coord c, Color color) {
if (c == Coord::kPass || c == Coord::kResign) {
PassOrResignMove(c);
return;
}
if (color == Color::kEmpty) {
color = to_play_;
} else {
to_play_ = color;
}
MG_DCHECK(ClassifyMove(c) != MoveType::kIllegal) << c;
AddStoneToBoard(c, color);
n_ += 1;
to_play_ = OtherColor(to_play_);
previous_move_ = c;
}
std::string Position::ToSimpleString() const {
std::ostringstream oss;
for (int row = 0; row < kN; ++row) {
for (int col = 0; col < kN; ++col) {
Coord c(row, col);
auto color = stones_[c].color();
if (color == Color::kWhite) {
oss << "O";
} else if (color == Color::kBlack) {
oss << "X";
} else {
oss << (c == ko_ ? "*" : ".");
}
}
if (row + 1 < kN) {
oss << "\n";
}
}
return oss.str();
}
std::string Position::ToPrettyString(bool use_ansi_colors) const {
std::ostringstream oss;
auto format_cols = [&oss]() {
oss << " ";
for (int i = 0; i < kN; ++i) {
oss << Coord::kKgsColumns[i] << " ";
}
};
const char* print_white = use_ansi_colors ? kPrintWhite : "";
const char* print_black = use_ansi_colors ? kPrintBlack : "";
const char* print_empty = use_ansi_colors ? kPrintEmpty : "";
const char* print_normal = use_ansi_colors ? kPrintNormal : "";
format_cols();
oss << "\n";
for (int row = 0; row < kN; ++row) {
oss << absl::StreamFormat("%2d ", kN - row);
for (int col = 0; col < kN; ++col) {
Coord c(row, col);
auto color = stones_[c].color();
if (color == Color::kWhite) {
oss << print_white << "O ";
} else if (color == Color::kBlack) {
oss << print_black << "X ";
} else {
oss << print_empty << (c == ko_ ? "* " : ". ");
}
}
oss << print_normal << absl::StreamFormat("%2d", kN - row);
oss << "\n";
}
format_cols();
return oss.str();
}
void Position::PassOrResignMove(Coord c) {
n_ += 1;
ko_ = Coord::kInvalid;
to_play_ = OtherColor(to_play_);
previous_move_ = c;
}
void Position::AddStoneToBoard(Coord c, Color color) {
auto potential_ko = IsKoish(c);
auto opponent_color = OtherColor(color);
// Traverse the coord's neighbors, building useful information:
// - list of captured groups (if any).
// - coordinates of the new stone's liberties.
// - set of neighboring groups of each color.
inline_vector<std::pair<GroupId, Coord>, 4> captured_groups;
inline_vector<Coord, 4> liberties;
tiny_set<GroupId, 4> opponent_groups;
tiny_set<GroupId, 4> neighbor_groups;
for (auto nc : kNeighborCoords[c]) {
auto neighbor = stones_[nc];
auto neighbor_color = neighbor.color();
auto neighbor_group_id = neighbor.group_id();
if (neighbor_color == Color::kEmpty) {
// Remember the coord of this liberty.
liberties.push_back(nc);
} else if (neighbor_color == color) {
// Remember neighboring groups of same color.
neighbor_groups.insert(neighbor_group_id);
} else if (neighbor_color == opponent_color) {
// Decrement neighboring opponent group liberty counts and remember the
// gorups we have captured. We'll remove them from the board shortly.
if (opponent_groups.insert(neighbor_group_id)) {
Group& opponent_group = groups_[neighbor_group_id];
if (--opponent_group.num_liberties == 0) {
captured_groups.emplace_back(neighbor_group_id, nc);
}
}
}
}
// Place the new stone on the board.
if (neighbor_groups.empty()) {
// The stone doesn't connect to any neighboring groups: create a new group.
stones_[c] = {color, groups_.alloc(1, liberties.size())};
} else {
// The stone connects to at least one neighbor: merge it into the first
// group we found.
auto group_id = neighbor_groups[0];
if (neighbor_groups.size() == 1) {
// Only one neighbor: update the group's size and liberty count, being
// careful not to add count coords that were already liberties of the
// group.
Group& group = groups_[group_id];
++group.size;
--group.num_liberties;
for (auto nc : liberties) {
if (!HasNeighboringGroup(nc, group_id)) {
++group.num_liberties;
}
}
stones_[c] = {color, group_id};
} else {
// The stone joins multiple groups, merge them.
// Incrementally updating the merged liberty counts is hard, so we just
// recalculate the merged group's size and liberty count from scratch.
// This is the relatively infrequent slow path.
stones_[c] = {color, group_id};
MergeGroup(c);
for (int i = 1; i < neighbor_groups.size(); ++i) {
groups_.free(neighbor_groups[i]);
}
}
}
stone_hash_ ^= zobrist::MoveHash(c, color);
// Remove captured groups.
for (const auto& p : captured_groups) {
int num_captured_stones = groups_[p.first].size;
if (color == Color::kBlack) {
num_captures_[0] += num_captured_stones;
} else {
num_captures_[1] += num_captured_stones;
}
RemoveGroup(p.second);
}
// Update ko.
if (captured_groups.size() == 1 &&
groups_[captured_groups[0].first].size == 1 &&
potential_ko == opponent_color) {
ko_ = captured_groups[0].second;
} else {
ko_ = Coord::kInvalid;
}
}
void Position::RemoveGroup(Coord c) {
// Remember the first stone from the group we're about to remove.
auto removed_color = stones_[c].color();
auto other_color = OtherColor(removed_color);
auto removed_group_id = stones_[c].group_id();
group_visitor_->Begin();
board_visitor_->Begin();
board_visitor_->Visit(c);
while (!board_visitor_->Done()) {
c = board_visitor_->Next();
MG_CHECK(stones_[c].group_id() == removed_group_id);
stones_[c] = {};
stone_hash_ ^= zobrist::MoveHash(c, removed_color);
tiny_set<GroupId, 4> other_groups;
for (auto nc : kNeighborCoords[c]) {
auto ns = stones_[nc];
auto neighbor_color = ns.color();
auto neighbor_group_id = ns.group_id();
if (neighbor_color == other_color) {
if (other_groups.insert(neighbor_group_id)) {
++groups_[neighbor_group_id].num_liberties;
}
} else if (neighbor_color == removed_color) {
board_visitor_->Visit(nc);
}
}
}
groups_.free(removed_group_id);
}
void Position::MergeGroup(Coord c) {
Stone s = stones_[c];
Color color = s.color();
Color opponent_color = OtherColor(color);
Group& group = groups_[s.group_id()];
group.num_liberties = 0;
group.size = 0;
board_visitor_->Begin();
board_visitor_->Visit(c);
while (!board_visitor_->Done()) {
c = board_visitor_->Next();
if (stones_[c].color() == Color::kEmpty) {
++group.num_liberties;
} else {
MG_CHECK(stones_[c].color() == color);
++group.size;
stones_[c] = s;
for (auto nc : kNeighborCoords[c]) {
if (stones_[nc].color() != opponent_color) {
// We visit neighboring stones of the same color and empty coords.
// Visiting empty coords through the BoardVisitor API ensures that
// each one is only counted as a liberty once, even if it is
// neighbored by multiple stones in this group.
board_visitor_->Visit(nc);
}
}
}
}
}
Color Position::IsKoish(Coord c) const {
if (!stones_[c].empty()) {
return Color::kEmpty;
}
Color ko_color = Color::kEmpty;
for (Coord nc : kNeighborCoords[c]) {
Stone s = stones_[nc];
if (s.empty()) {
return Color::kEmpty;
}
if (s.color() != ko_color) {
if (ko_color == Color::kEmpty) {
ko_color = s.color();
} else {
return Color::kEmpty;
}
}
}
return ko_color;
}
Position::MoveType Position::ClassifyMove(Coord c) const {
if (c == Coord::kPass || c == Coord::kResign) {
return MoveType::kNoCapture;
}
if (!stones_[c].empty()) {
return MoveType::kIllegal;
}
if (c == ko_) {
return MoveType::kIllegal;
}
auto result = MoveType::kIllegal;
auto other_color = OtherColor(to_play_);
for (auto nc : kNeighborCoords[c]) {
Stone s = stones_[nc];
if (s.empty()) {
// At least one liberty at nc after playing at c.
if (result == MoveType::kIllegal) {
result = MoveType::kNoCapture;
}
} else if (s.color() == other_color) {
if (groups_[s.group_id()].num_liberties == 1) {
// Will capture opponent group that has a stone at nc.
result = MoveType::kCapture;
}
} else {
if (groups_[s.group_id()].num_liberties > 1) {
// Connecting to a same colored group at nc that has more than one
// liberty.
if (result == MoveType::kIllegal) {
result = MoveType::kNoCapture;
}
}
}
}
return result;
}
bool Position::HasNeighboringGroup(Coord c, GroupId group_id) const {
for (auto nc : kNeighborCoords[c]) {
Stone s = stones_[nc];
if (!s.empty() && s.group_id() == group_id) {
return true;
}
}
return false;
}
float Position::CalculateScore(float komi) {
int score = 0;
static_assert(static_cast<int>(Color::kEmpty) == 0, "Color::kEmpty != 0");
static_assert(static_cast<int>(Color::kBlack) == 1, "Color::kBlack != 1");
static_assert(static_cast<int>(Color::kWhite) == 2, "Color::kWhite != 2");
auto score_empty_area = [this](Coord c) {
int num_visited = 0;
int found_bits = 0;
do {
c = board_visitor_->Next();
++num_visited;
for (auto nc : kNeighborCoords[c]) {
Color color = stones_[nc].color();
if (color == Color::kEmpty) {
board_visitor_->Visit(nc);
} else {
found_bits |= static_cast<int>(color);
}
}
} while (!board_visitor_->Done());
if (found_bits == 1) {
return num_visited;
} else if (found_bits == 2) {
return -num_visited;
} else {
return 0;
}
};
group_visitor_->Begin();
board_visitor_->Begin();
for (int row = 0; row < kN; ++row) {
for (int col = 0; col < kN; ++col) {
Coord c(row, col);
Stone s = stones_[c];
if (s.empty()) {
if (board_visitor_->Visit(c)) {
// First time visiting this empty coord.
score += score_empty_area(c);
}
} else if (group_visitor_->Visit(s.group_id())) {
// First time visiting this group of stones.
auto size = groups_[s.group_id()].size;
if (s.color() == Color::kBlack) {
score += size;
} else {
score -= size;
}
}
}
}
return static_cast<float>(score) - komi;
}
} // namespace minigo