/usr/include/sdsl/wt_hutu.hpp is in libsdsl-dev 2.0.3-4.
This file is owned by root:root, with mode 0o644.
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Copyright (C) 2013 Simon Gog, Timo Beller and Markus Brenner
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see http://www.gnu.org/licenses/ .
*/
/*! \file wt_hutu.hpp
\brief wt_hutu.hpp contains a class for a Hu-Tucker shaped wavelet tree
over byte sequences.
\author Simon Gog, Markus Brenner
*/
#ifndef INCLUDED_SDSL_WT_HUTU
#define INCLUDED_SDSL_WT_HUTU
#include "wt_pc.hpp"
#include <vector>
//! Namespace for the succinct data structure library.
namespace sdsl
{
// forward declaration
struct hutu_shape;
//! A Hu-Tucker-shaped wavelet tree.
/*!
* \tparam t_bitvector Underlying bitvector structure.
* \tparam t_rank Rank support for pattern `1` on the bitvector.
* \tparam t_select Select support for pattern `1` on the bitvector.
* \tparam t_select_zero Select support for pattern `0` on the bitvector.
* \tparam t_dfs_shape Layout of the tree structure in memory. Set 0
* for BFS layout and 1 fro DFS layout.
* \par Space complexity
* Almost \f$n H_0 + 2|\Sigma|\log n\f$ bits, where \f$n\f$ is the size of
* the vector the wavelet tree was build for.
*
* @ingroup wt
*/
template<class t_bitvector = bit_vector,
class t_rank = typename t_bitvector::rank_1_type,
class t_select = typename t_bitvector::select_1_type,
class t_select_zero = typename t_bitvector::select_0_type,
class t_tree_strat = byte_tree<> >
using wt_hutu = wt_pc<hutu_shape,
t_bitvector,
t_rank,
t_select,
t_select_zero,
t_tree_strat>;
// Hu Tucker shape for wt_pc
template<class t_wt>
struct _hutu_shape {
typedef typename t_wt::size_type size_type;
enum { lex_ordered = 1 };
//! Node class used by the leftist heap
template <class t_element>
struct heap_node {
t_element* item; // pointer to the represented item
heap_node* left, *right, *parent; // pointer to left/right child, parent
int64_t rank; // rank of the heap node
//! Constructor
heap_node(t_element* it=nullptr) : item(it), left(nullptr),
right(nullptr), parent(nullptr),
rank(0) { }
//! Less then operator
bool operator< (const heap_node& other) {
return *item < *(other.item);
}
};
// Implementation of a leftist heap as needed in the first phase of
// Hu-Tucker Code construction
template <class t_element>
class l_heap
{
private:
heap_node<t_element>* m_root; // pointer to the root
// fixes node information after the deletion of elements
void fix_node(heap_node<t_element>* item) {
if (item != nullptr) {
if (!item->left || !item->right) { // if node has only one child
// only go on fixing if the node information needs to be changed
if (item->rank != 0) {
item->rank = 0;
if (item->parent) fix_node(item->parent);
}
} else { // node information has to be adapted
int64_t nn = (item->left->rank > item->right->rank) ? item->right->rank : item->left->rank;
if (item->rank != nn && item->parent != 0) {
item->rank = nn;
fix_node(item->parent);
}
}
}
}
// helper function to remove the data structure from memory
void free_node(heap_node<t_element>* item) {
if (item->left) {
free_node(item->left);
delete item->left;
item->left = nullptr;
}
if (item->right) {
free_node(item->right);
delete item->right;
item->right = nullptr;
}
}
// internal merge function
heap_node<t_element>* merge(heap_node<t_element>* h1, heap_node<t_element>* h2) {
if (!h1) return h2;
if (!h2) return h1;
if (*(h1->item) < *(h2->item)) return merge1(h1, h2);
else return merge1(h2, h1);
}
// internal merge function
heap_node<t_element>* merge1(heap_node<t_element>* h1, heap_node<t_element>* h2) {
if (!h1->left) { // if h1 has no children, the merge is simple
h1->left = h2;
h2->parent = h1; // adjust the parent pointer
} else {
h1->right = merge(h1->right, h2);
if (h1->right) h1->right->parent = h1;
if (h1->left->rank < h1->right->rank) {
heap_node<t_element>* tmp = h1->left;
h1->left = h1->right;
h1->right = tmp;
}
h1 -> rank = h1 -> right -> rank + 1;
}
return h1;
}
public:
//! Default constructor
l_heap() : m_root(nullptr) { }
//! Indicates if the heap is empty
bool empty() const {
return (m_root==nullptr);
}
//! Get the smallest element
/*! \return The smallest element in the heap
* or nullptr if it does not exist.
*/
heap_node<t_element>* find_min() const {
return m_root;
}
//! Get the second smallest element
/*! \return The second smallest element in the heap
* or nullptr if it does not exist.
*/
heap_node<t_element>* find_snd_min() const {
if (m_root == nullptr) return nullptr;
if (m_root->left == nullptr) return m_root->right;
if (m_root->right == nullptr) return m_root->left;
if (m_root->left->operator< (*m_root->right)) return m_root->left;
else return m_root->right;
}
//! Insert an element into the heap
/*! \param x Element that is inserted into the heap.
* \return The new generated heap node.
*/
heap_node<t_element>* insert(t_element* x) {
heap_node<t_element>* n = new heap_node<t_element>(x);
l_heap<t_element> lh;
lh.m_root = n;
merge(&lh);
return n;
}
//! Delete the smallest element in the heap
void delete_min() {
heap_node<t_element>* old_root = m_root;
m_root = merge(m_root->left, m_root->right);
if (m_root) m_root->parent = nullptr;
delete old_root;
}
// deletes an arbitrary element from the heap
// this function assumes, that item is an element of the heap
void delete_element(heap_node<t_element>* item) {
if (item != nullptr) {
if (m_root == item) { // deleting the root is trivial
delete_min();
} else {
// otherwise we have to adapt the parent node and
// the children of item
heap_node<t_element>* h1 = merge(item->left,item->right);
if (h1) h1->parent = item->parent;
if (item == item->parent->left) {
item->parent->left = h1;
} else if (item == item->parent->right) {
item->parent->right = h1;
}
// fix node information considering rank
fix_node(item->parent);
delete item; // remove the item from memory
}
}
}
// public merge function
void merge(l_heap<t_element>* rhs) {
m_root = merge(m_root, rhs->m_root);
rhs->m_root = nullptr;
}
// removes the whole data structure from memory
void free_memory() {
if (m_root != nullptr) {
free_node(m_root);
delete m_root;
m_root = nullptr;
}
}
};
// forward declaration of node classes
struct ht_node;
// Master node as used in the first phase of the Hu-Tucker algorithm
struct m_node {
// min sum of the two min elements of the hpq this node points to
size_type min_sum;
int64_t i; // position of the left node in the working sequence
int64_t j; // position of the right node in the working sequence
// pointer to the corresponding heap element (used for deletion)
heap_node<m_node>* qel;
l_heap<ht_node>* myhpq; // pointer to the hpq
ht_node* lt; // pointer to the left- and rightmost leafs of the hpq
ht_node* rt; // need for merge operations
m_node() : qel(0), myhpq(0), lt(0), rt(0) { }
bool operator<(const m_node other) {
if (min_sum != other.min_sum) {
return min_sum < other.min_sum;
}
if (i != other.i) {
return i < other.i;
}
return j < other.j;
}
bool operator> (const m_node other) {
return other < *this;
}
};
// Hu-Tucker node as used in the first phase of the Hu-Tucker algorithm
struct ht_node {
int64_t pos; // position of the node
uint64_t c; // the represented letter
size_type w; // frequency of the node
bool t; // whether the node is a leaf
int64_t level; // level in the tree
// pointer to the two master nodes
// (as a node can belong to up to two hpqs)
m_node* mpql;
m_node* mpqr; // only mpql is used for inner nodes
// pointer to the two heap nodes (as a node can belong to up to two hpqs)
heap_node<ht_node>* ql;
heap_node<ht_node>* qr; // only ql is used for inner nodes
ht_node* left; // left child
ht_node* right; // right child
ht_node() : mpql(0), mpqr(0), ql(0), qr(0),
left(nullptr), right(nullptr) { }
bool operator< (const ht_node& other) {
if (w != other.w) {
return w < other.w;
}
return pos < other.pos;
}
bool operator> (const ht_node& other) {
return other < *this;
}
};
template<class t_rac>
static void
construct_tree(t_rac& C, std::vector<pc_node>& temp_nodes) {
//create a leaf for every letter
std::vector<ht_node> node_vector;
for (size_t i = 0; i < C.size(); i++) {
if (C[i]) {
ht_node n;
n.c = (uint64_t)i;
n.w = C[i];
n.t = true;
n.pos = node_vector.size();
node_vector.push_back(n);
}
}
if (node_vector.size() == 1) {
// special case of an alphabet of size 1:
// just instantly create the tree and return it
temp_nodes.emplace_back(pc_node(node_vector[0].w,
(size_type)node_vector[0].c));
return;
}
size_type sigma = node_vector.size();
std::vector<ht_node> T(sigma); // physical leaves
std::vector<ht_node*> A(sigma); // the current working sequence
// Priority Queues, containing the Huffman Sequences
std::vector<l_heap<ht_node>> HPQ(sigma);
l_heap<m_node> MPQ; // Master Priority Queue
// init T, A, HPQs and MPQ
T[0] = node_vector[0];
A[0] = &T[0];
// initialization needed for every leaf
for (size_type i = 1; i < sigma; i++) {
T[i] = node_vector[i];
A[i] = &T[i];
T[i - 1].qr = HPQ[i - 1].insert(&T[i - 1]);
T[i].ql = HPQ[i - 1].insert(&T[i]);
m_node* m = new m_node();
m->min_sum = T[i - 1].w + T[i].w;
m->i = i - 1;
m->j = i;
m->lt = &T[i-1];
m->rt = &T[i];
m->myhpq = &HPQ[i - 1];
m->qel = MPQ.insert(m);
T[i-1].mpqr = m;
T[i].mpql = m;
}
// main action loop
for (size_type k = 1; k < sigma; k++) {
m_node* m = MPQ.find_min()->item;
ht_node* l = A[m->i];
ht_node* r = A[m->j];
int64_t lpos = m->i;
int64_t rpos = m->j;
l_heap<ht_node>* n_hpq = nullptr;
ht_node* n_rt = nullptr;
ht_node* n_lt = nullptr;
// create a new master priority queue
m_node* n_m = new m_node();
// delete old nodes from all hpqs
if (l->t) {
if (l->mpql) l->mpql->myhpq->delete_element(l->ql);
l->ql = nullptr;
if (l->mpqr) l->mpqr->myhpq->delete_element(l->qr);
l->qr = nullptr;
} else {
m->myhpq->delete_element(l->ql);
l->ql = nullptr;
}
if (r->t) {
if (r->mpql) r->mpql->myhpq->delete_element(r->ql);
l->ql = nullptr;
if (r->mpqr) r->mpqr->myhpq->delete_element(r->qr);
r->qr = nullptr;
} else {
m->myhpq->delete_element(r->ql);
r->ql = nullptr;
}
// handle the merge of hpqs
if (l->t && r ->t) {
// both nodes are leaves
l_heap<ht_node>* h1 = nullptr;
l_heap<ht_node>* h2 = nullptr;
l_heap<ht_node>* h3 = nullptr;
if (l -> mpql) {
n_lt = l->mpql->lt;
if (n_lt == l) n_lt = nullptr;
if (n_lt) n_lt -> mpqr = n_m;
h1 = l->mpql->myhpq;
h2 = l->mpqr->myhpq;
h1 -> merge(h2);
MPQ.delete_element(l->mpql->qel);
MPQ.delete_element(l->mpqr->qel);
delete l->mpql;
delete l->mpqr;
} else {
h1 = l->mpqr->myhpq;
h2 = l->mpqr->myhpq;
n_lt = nullptr;
MPQ.delete_element(l->mpqr->qel);
delete l->mpqr;
}
if (r->mpqr) {
n_rt = r->mpqr->rt;
if (n_rt == r) n_rt = nullptr;
if (n_rt) n_rt -> mpql = n_m;
h3 = r->mpqr->myhpq;
h1->merge(h3);
MPQ.delete_element(r->mpqr->qel);
delete r->mpqr;
n_hpq = h1;
if (n_rt) n_rt -> mpql = n_m;
} else {
n_rt = nullptr;
n_hpq = h1;
}
} else if (l->t) { // the left node is a leaf
if (l->mpql) {
n_lt = l->mpql->lt;
if (n_lt) n_lt->mpqr = n_m;
n_rt = l->mpqr->rt;
if (n_rt) n_rt ->mpql = n_m;
l -> mpql ->myhpq -> merge(l->mpqr->myhpq);
n_hpq=l->mpql->myhpq;
MPQ.delete_element(l->mpql->qel);
MPQ.delete_element(l->mpqr->qel);
delete l->mpql;
delete l->mpqr;
} else {
n_lt = nullptr;
n_rt = l->mpqr->rt;
if (n_rt) n_rt->mpql = n_m;
n_hpq = l->mpqr->myhpq;
MPQ.delete_element(l->mpqr->qel);
delete l->mpqr;
}
} else if (r->t) { // right node is a leaf
if (r->mpqr) {
n_lt = r->mpql->lt;
if (n_lt) n_lt->mpqr = n_m;
n_rt = r->mpqr->rt;
if (n_rt) n_rt->mpql = n_m;
r -> mpql ->myhpq -> merge(r->mpqr->myhpq);
n_hpq=r->mpql->myhpq;
MPQ.delete_element(r->mpql->qel);
MPQ.delete_element(r->mpqr->qel);
delete r->mpql;
delete r->mpqr;
} else {
n_lt = r->mpql->lt;
if (n_lt) n_lt->mpqr = n_m;
n_rt = nullptr;
n_hpq = r->mpql->myhpq;
MPQ.delete_element(r->mpql->qel);
delete r->mpql;
}
} else {
// merge of two inner nodes
// no need to merge hpqs
MPQ.delete_element(m->qel);
n_hpq = m->myhpq;
n_lt = m->lt;
n_rt = m->rt;
if (n_lt) n_lt->mpqr = n_m;
if (n_rt) n_rt->mpql = n_m;
delete m;
}
// create a new node with the information gained above
ht_node* new_node = new ht_node();
new_node -> c = ' ';
new_node -> w = l->w + r->w;
new_node -> t = false;
new_node -> pos = lpos;
new_node -> left = l;
new_node -> right = r;
// insert node to the correct hpq
new_node -> ql = n_hpq->insert(new_node);
// update working sequence
A[lpos] = new_node;
A[rpos] = nullptr;
// update information in the new master node and reinsert it to mpq
ht_node* tmp_min = n_hpq->find_min()->item;
heap_node<ht_node>* tmpsnd = n_hpq->find_snd_min();
if (tmpsnd) {
ht_node* tmp_snd = n_hpq->find_snd_min()->item;
n_m->min_sum = tmp_min->w + tmp_snd->w;
if (tmp_min -> pos < tmp_snd->pos) {
n_m->i = tmp_min -> pos;
n_m->j = tmp_snd -> pos;
} else {
n_m->i = tmp_snd -> pos;
n_m->j = tmp_min -> pos;
}
n_m->qel = MPQ.insert(n_m);
n_m->myhpq = n_hpq;
n_m->lt = n_lt;
n_m->rt = n_rt;
} else {
// free the last remaining hpq
n_hpq->free_memory();
delete n_m;
}
}
// level assignment and deletion of unneeded nodes
assign_level(A[0], 0);
// reconstruction phase using the stack algorithm
ht_node* stack[sigma];
for (size_type i = 0; i < sigma; i++) {
stack[i] = nullptr;
temp_nodes.emplace_back(pc_node(T[i].w, (size_type)T[i].c));
T[i].pos = i;
}
int64_t spointer = -1;
uint64_t qpointer = 0; // use the Array T as a stack
int64_t max_nodes = sigma;
while (qpointer < sigma or spointer >= 1LL) {
if (spointer >= 1LL and
(stack[spointer]->level == stack[spointer-1]->level)) {
ht_node* n_node = new ht_node();
max_nodes++;
n_node->t = false;
n_node->left = stack[spointer-1];
n_node->right = stack[spointer];
n_node->level = stack[spointer]->level-1;
n_node->w = stack[spointer]->w + stack[spointer-1]->w;
n_node->c = '|';
n_node->pos = temp_nodes.size();
temp_nodes[stack[spointer-1]->pos].parent = temp_nodes.size();
temp_nodes[stack[spointer]->pos].parent = temp_nodes.size();
temp_nodes.emplace_back(pc_node(n_node->w, 0,
pc_node::undef,
stack[spointer-1]->pos,
stack[spointer]->pos));
if (!stack[spointer-1]->t) delete stack[spointer-1];
if (!stack[spointer]->t) delete stack[spointer];
stack[--spointer] = n_node;
} else {
stack[++spointer] = &T[qpointer++];
}
}
delete stack[0];
}
static void assign_level(ht_node* n, int64_t lvl) {
if (n) {
n->level = lvl;
assign_level(n->left, lvl + 1);
assign_level(n->right, lvl + 1);
if (!n->t) {
delete n;
}
}
}
};
struct hutu_shape {
template<class t_wt>
using type = _hutu_shape<t_wt>;
};
}// end namespace sdsl
#endif // end file
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