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80 lines (66 loc) · 2.48 KB
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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.
#ifndef CC_GROUP_H_
#define CC_GROUP_H_
#include <cstdint>
#include "cc/constants.h"
#include "cc/inline_vector.h"
namespace minigo {
// GroupId is a unique identifier for a group (string) of stones.
using GroupId = uint16_t;
// Group represents a group (string) of stones.
// A group only keeps track of the count of its current liberties, not their
// location.
struct Group {
Group() = default;
Group(uint16_t size, uint16_t num_liberties)
: size(size), num_liberties(num_liberties) {}
// Maximum number of potential groups on the board.
// Used in various places to pre-allocate buffers.
// TODO(tommadams): We can probably reduce the space reserved for potential
// groups a bit: https://senseis.xmp.net/?MaximumNumberOfLiveGroups
static constexpr int kMaxNumGroups = kN * kN;
uint16_t size = 0;
uint16_t num_liberties = 0;
};
// GroupPool is a simple memory pool for Group objects.
class GroupPool {
public:
// Allocates a new Group with the given size and number of liberties, and
// returns the group's ID.
GroupId alloc(uint16_t size, uint16_t num_liberties) {
GroupId id;
if (!free_ids_.empty()) {
// We have at least one previously acclocated then freed group, return it.
id = free_ids_.back();
free_ids_.pop_back();
groups_[id] = {size, num_liberties};
} else {
// Allocate a new group from the pool.
id = static_cast<GroupId>(groups_.size());
groups_.emplace_back(size, num_liberties);
}
return id;
}
// Free the group, returning it the pool.
void free(GroupId id) { free_ids_.push_back(id); }
// Access the Group object by ID.
Group& operator[](GroupId id) { return groups_[id]; }
const Group& operator[](GroupId id) const { return groups_[id]; }
private:
inline_vector<Group, Group::kMaxNumGroups> groups_;
inline_vector<GroupId, Group::kMaxNumGroups> free_ids_;
};
} // namespace minigo
#endif // CC_GROUP_H_