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// Ceres Solver - A fast non-linear least squares minimizer
// Copyright 2019 Google Inc. All rights reserved.
// http://ceres-solver.org/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// * Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
// and/or other materials provided with the distribution.
// * Neither the name of Google Inc. nor the names of its contributors may be
// used to endorse or promote products derived from this software without
// specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.
//
// Author: sameeragarwal@google.com (Sameer Agarwal)
#ifndef CERES_PUBLIC_ORDERED_GROUPS_H_
#define CERES_PUBLIC_ORDERED_GROUPS_H_
#include <map>
#include <set>
#include <unordered_map>
#include <vector>
#include "ceres/internal/export.h"
#include "glog/logging.h"
namespace ceres {
// A class for storing and manipulating an ordered collection of
// groups/sets with the following semantics:
//
// Group ids are non-negative integer values. Elements are any type
// that can serve as a key in a map or an element of a set.
//
// An element can only belong to one group at a time. A group may
// contain an arbitrary number of elements.
//
// Groups are ordered by their group id.
template <typename T>
class OrderedGroups {
public:
// Add an element to a group. If a group with this id does not
// exist, one is created. This method can be called any number of
// times for the same element. Group ids should be non-negative
// numbers.
//
// Return value indicates if adding the element was a success.
bool AddElementToGroup(const T element, const int group) {
if (group < 0) {
return false;
}
auto it = element_to_group_.find(element);
if (it != element_to_group_.end()) {
if (it->second == group) {
// Element is already in the right group, nothing to do.
return true;
}
group_to_elements_[it->second].erase(element);
if (group_to_elements_[it->second].size() == 0) {
group_to_elements_.erase(it->second);
}
}
element_to_group_[element] = group;
group_to_elements_[group].insert(element);
return true;
}
void Clear() {
group_to_elements_.clear();
element_to_group_.clear();
}
// Remove the element, no matter what group it is in. Return value
// indicates if the element was actually removed.
bool Remove(const T element) {
const int current_group = GroupId(element);
if (current_group < 0) {
return false;
}
group_to_elements_[current_group].erase(element);
if (group_to_elements_[current_group].size() == 0) {
// If the group is empty, then get rid of it.
group_to_elements_.erase(current_group);
}
element_to_group_.erase(element);
return true;
}
// Bulk remove elements. The return value indicates the number of
// elements successfully removed.
int Remove(const std::vector<T>& elements) {
if (NumElements() == 0 || elements.size() == 0) {
return 0;
}
int num_removed = 0;
for (int i = 0; i < elements.size(); ++i) {
num_removed += Remove(elements[i]);
}
return num_removed;
}
// Reverse the order of the groups in place.
void Reverse() {
if (NumGroups() == 0) {
return;
}
auto it = group_to_elements_.rbegin();
std::map<int, std::set<T>> new_group_to_elements;
new_group_to_elements[it->first] = it->second;
int new_group_id = it->first + 1;
for (++it; it != group_to_elements_.rend(); ++it) {
for (const auto& element : it->second) {
element_to_group_[element] = new_group_id;
}
new_group_to_elements[new_group_id] = it->second;
new_group_id++;
}
group_to_elements_.swap(new_group_to_elements);
}
// Return the group id for the element. If the element is not a
// member of any group, return -1.
int GroupId(const T element) const {
auto it = element_to_group_.find(element);
if (it == element_to_group_.end()) {
return -1;
}
return it->second;
}
bool IsMember(const T element) const {
auto it = element_to_group_.find(element);
return (it != element_to_group_.end());
}
// This function always succeeds, i.e., implicitly there exists a
// group for every integer.
int GroupSize(const int group) const {
auto it = group_to_elements_.find(group);
return (it == group_to_elements_.end()) ? 0 : it->second.size();
}
int NumElements() const { return element_to_group_.size(); }
// Number of groups with one or more elements.
int NumGroups() const { return group_to_elements_.size(); }
// The first group with one or more elements. Calling this when
// there are no groups with non-zero elements will result in a
// crash.
int MinNonZeroGroup() const {
CHECK_NE(NumGroups(), 0);
return group_to_elements_.begin()->first;
}
const std::map<int, std::set<T>>& group_to_elements() const {
return group_to_elements_;
}
const std::map<T, int>& element_to_group() const { return element_to_group_; }
private:
std::map<int, std::set<T>> group_to_elements_;
std::unordered_map<T, int> element_to_group_;
};
// Typedef for the most commonly used version of OrderedGroups.
using ParameterBlockOrdering = OrderedGroups<double*>;
} // namespace ceres
#endif // CERES_PUBLIC_ORDERED_GROUP_H_
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