648 lines
17 KiB
C++
648 lines
17 KiB
C++
// Copyright 2004 The Trustees of Indiana University.
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// Use, modification and distribution is subject to the Boost Software
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// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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// Authors: Douglas Gregor
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// Andrew Lumsdaine
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#ifndef BOOST_RELAXED_HEAP_HEADER
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#define BOOST_RELAXED_HEAP_HEADER
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#include <functional>
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#include <boost/property_map/property_map.hpp>
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#include <boost/optional.hpp>
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#include <vector>
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#include <climits> // for CHAR_BIT
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#include <boost/none.hpp>
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#ifdef BOOST_RELAXED_HEAP_DEBUG
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# include <iostream>
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#endif // BOOST_RELAXED_HEAP_DEBUG
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#if defined(BOOST_MSVC)
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# pragma warning(push)
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# pragma warning(disable:4355) // complaint about using 'this' to
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#endif // initialize a member
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namespace boost {
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template<typename IndexedType,
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typename Compare = std::less<IndexedType>,
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typename ID = identity_property_map>
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class relaxed_heap
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{
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struct group;
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typedef relaxed_heap self_type;
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typedef std::size_t rank_type;
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public:
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typedef IndexedType value_type;
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typedef rank_type size_type;
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private:
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/**
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* The kind of key that a group has. The actual values are discussed
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* in-depth in the documentation of the @c kind field of the @c group
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* structure. Note that the order of the enumerators *IS* important
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* and must not be changed.
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*/
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enum group_key_kind { smallest_key, stored_key, largest_key };
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struct group {
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explicit group(group_key_kind kind = largest_key)
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: kind(kind), parent(this), rank(0) { }
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/** The value associated with this group. This value is only valid
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* when @c kind!=largest_key (which indicates a deleted
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* element). Note that the use of boost::optional increases the
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* memory requirements slightly but does not result in extraneous
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* memory allocations or deallocations. The optional could be
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* eliminated when @c value_type is a model of
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* DefaultConstructible.
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*/
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::boost::optional<value_type> value;
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/**
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* The kind of key stored at this group. This may be @c
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* smallest_key, which indicates that the key is infinitely small;
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* @c largest_key, which indicates that the key is infinitely
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* large; or @c stored_key, which means that the key is unknown,
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* but its relationship to other keys can be determined via the
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* comparison function object.
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*/
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group_key_kind kind;
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/// The parent of this group. Will only be NULL for the dummy root group
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group* parent;
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/// The rank of this group. Equivalent to the number of children in
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/// the group.
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rank_type rank;
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/** The children of this group. For the dummy root group, these are
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* the roots. This is an array of length log n containing pointers
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* to the child groups.
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*/
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group** children;
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};
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size_type log_base_2(size_type n) // log2 is a macro on some platforms
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{
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size_type leading_zeroes = 0;
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do {
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size_type next = n << 1;
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if (n == (next >> 1)) {
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++leading_zeroes;
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n = next;
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} else {
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break;
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}
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} while (true);
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return sizeof(size_type) * CHAR_BIT - leading_zeroes - 1;
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}
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public:
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relaxed_heap(size_type n, const Compare& compare = Compare(),
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const ID& id = ID())
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: compare(compare), id(id), root(smallest_key), groups(n),
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smallest_value(0)
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{
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if (n == 0) {
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root.children = new group*[1];
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return;
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}
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log_n = log_base_2(n);
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if (log_n == 0) log_n = 1;
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size_type g = n / log_n;
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if (n % log_n > 0) ++g;
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size_type log_g = log_base_2(g);
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size_type r = log_g;
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// Reserve an appropriate amount of space for data structures, so
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// that we do not need to expand them.
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index_to_group.resize(g);
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A.resize(r + 1, 0);
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root.rank = r + 1;
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root.children = new group*[(log_g + 1) * (g + 1)];
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for (rank_type i = 0; i < r+1; ++i) root.children[i] = 0;
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// Build initial heap
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size_type idx = 0;
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while (idx < g) {
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root.children[r] = &index_to_group[idx];
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idx = build_tree(root, idx, r, log_g + 1);
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if (idx != g)
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r = static_cast<size_type>(log_base_2(g-idx));
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}
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}
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~relaxed_heap() { delete [] root.children; }
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void push(const value_type& x)
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{
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groups[get(id, x)] = x;
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update(x);
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}
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void update(const value_type& x)
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{
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group* a = &index_to_group[get(id, x) / log_n];
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if (!a->value
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|| *a->value == x
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|| compare(x, *a->value)) {
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if (a != smallest_value) smallest_value = 0;
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a->kind = stored_key;
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a->value = x;
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promote(a);
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}
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}
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void remove(const value_type& x)
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{
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group* a = &index_to_group[get(id, x) / log_n];
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assert(groups[get(id, x)]);
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a->value = x;
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a->kind = smallest_key;
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promote(a);
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smallest_value = a;
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pop();
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}
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value_type& top()
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{
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find_smallest();
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assert(smallest_value->value != none);
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return *smallest_value->value;
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}
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const value_type& top() const
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{
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find_smallest();
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assert(smallest_value->value != none);
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return *smallest_value->value;
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}
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bool empty() const
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{
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find_smallest();
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return !smallest_value || (smallest_value->kind == largest_key);
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}
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bool contains(const value_type& x) const {
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return static_cast<bool>(groups[get(id, x)]);
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}
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void pop()
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{
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// Fill in smallest_value. This is the group x.
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find_smallest();
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group* x = smallest_value;
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smallest_value = 0;
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// Make x a leaf, giving it the smallest value within its group
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rank_type r = x->rank;
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group* p = x->parent;
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{
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assert(x->value != none);
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// Find x's group
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size_type start = get(id, *x->value) - get(id, *x->value) % log_n;
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size_type end = start + log_n;
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if (end > groups.size()) end = groups.size();
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// Remove the smallest value from the group, and find the new
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// smallest value.
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groups[get(id, *x->value)].reset();
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x->value.reset();
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x->kind = largest_key;
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for (size_type i = start; i < end; ++i) {
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if (groups[i] && (!x->value || compare(*groups[i], *x->value))) {
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x->kind = stored_key;
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x->value = groups[i];
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}
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}
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}
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x->rank = 0;
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// Combine prior children of x with x
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group* y = x;
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for (size_type c = 0; c < r; ++c) {
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group* child = x->children[c];
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if (A[c] == child) A[c] = 0;
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y = combine(y, child);
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}
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// If we got back something other than x, let y take x's place
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if (y != x) {
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y->parent = p;
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p->children[r] = y;
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assert(r == y->rank);
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if (A[y->rank] == x)
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A[y->rank] = do_compare(y, p)? y : 0;
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}
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}
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#ifdef BOOST_RELAXED_HEAP_DEBUG
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/*************************************************************************
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* Debugging support *
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*************************************************************************/
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void dump_tree() { dump_tree(std::cout); }
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void dump_tree(std::ostream& out) { dump_tree(out, &root); }
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void dump_tree(std::ostream& out, group* p, bool in_progress = false)
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{
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if (!in_progress) {
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out << "digraph heap {\n"
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<< " edge[dir=\"back\"];\n";
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}
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size_type p_index = 0;
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if (p != &root) while (&index_to_group[p_index] != p) ++p_index;
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for (size_type i = 0; i < p->rank; ++i) {
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group* c = p->children[i];
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if (c) {
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size_type c_index = 0;
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if (c != &root) while (&index_to_group[c_index] != c) ++c_index;
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out << " ";
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if (p == &root) out << 'p'; else out << p_index;
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out << " -> ";
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if (c == &root) out << 'p'; else out << c_index;
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if (A[c->rank] == c) out << " [style=\"dotted\"]";
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out << ";\n";
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dump_tree(out, c, true);
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// Emit node information
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out << " ";
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if (c == &root) out << 'p'; else out << c_index;
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out << " [label=\"";
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if (c == &root) out << 'p'; else out << c_index;
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out << ":";
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size_type start = c_index * log_n;
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size_type end = start + log_n;
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if (end > groups.size()) end = groups.size();
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while (start != end) {
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if (groups[start]) {
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out << " " << get(id, *groups[start]);
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if (*groups[start] == *c->value) out << "(*)";
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}
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++start;
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}
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out << '"';
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if (do_compare(c, p)) {
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out << " ";
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if (c == &root) out << 'p'; else out << c_index;
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out << ", style=\"filled\", fillcolor=\"gray\"";
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}
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out << "];\n";
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} else {
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assert(p->parent == p);
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}
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}
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if (!in_progress) out << "}\n";
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}
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bool valid()
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{
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// Check that the ranks in the A array match the ranks of the
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// groups stored there. Also, the active groups must be the last
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// child of their parent.
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for (size_type r = 0; r < A.size(); ++r) {
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if (A[r] && A[r]->rank != r) return false;
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if (A[r] && A[r]->parent->children[A[r]->parent->rank-1] != A[r])
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return false;
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}
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// The root must have no value and a key of -Infinity
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if (root.kind != smallest_key) return false;
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return valid(&root);
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}
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bool valid(group* p)
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{
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for (size_type i = 0; i < p->rank; ++i) {
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group* c = p->children[i];
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if (c) {
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// Check link structure
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if (c->parent != p) return false;
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if (c->rank != i) return false;
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// A bad group must be active
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if (do_compare(c, p) && A[i] != c) return false;
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// Check recursively
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if (!valid(c)) return false;
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} else {
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// Only the root may
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if (p != &root) return false;
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}
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}
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return true;
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}
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#endif // BOOST_RELAXED_HEAP_DEBUG
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private:
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size_type
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build_tree(group& parent, size_type idx, size_type r, size_type max_rank)
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{
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group& this_group = index_to_group[idx];
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this_group.parent = &parent;
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++idx;
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this_group.children = root.children + (idx * max_rank);
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this_group.rank = r;
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for (size_type i = 0; i < r; ++i) {
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this_group.children[i] = &index_to_group[idx];
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idx = build_tree(this_group, idx, i, max_rank);
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}
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return idx;
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}
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void find_smallest() const
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{
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group** roots = root.children;
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if (!smallest_value) {
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std::size_t i;
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for (i = 0; i < root.rank; ++i) {
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if (roots[i] &&
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(!smallest_value || do_compare(roots[i], smallest_value))) {
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smallest_value = roots[i];
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}
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}
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for (i = 0; i < A.size(); ++i) {
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if (A[i] && (!smallest_value || do_compare(A[i], smallest_value)))
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smallest_value = A[i];
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}
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}
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}
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bool do_compare(group* x, group* y) const
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{
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return (x->kind < y->kind
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|| (x->kind == y->kind
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&& x->kind == stored_key
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&& compare(*x->value, *y->value)));
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}
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void promote(group* a)
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{
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assert(a != 0);
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rank_type r = a->rank;
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group* p = a->parent;
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assert(p != 0);
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if (do_compare(a, p)) {
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// s is the rank + 1 sibling
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group* s = p->rank > r + 1? p->children[r + 1] : 0;
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// If a is the last child of p
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if (r == p->rank - 1) {
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if (!A[r]) A[r] = a;
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else if (A[r] != a) pair_transform(a);
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} else {
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assert(s != 0);
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if (A[r + 1] == s) active_sibling_transform(a, s);
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else good_sibling_transform(a, s);
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}
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}
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}
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group* combine(group* a1, group* a2)
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{
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assert(a1->rank == a2->rank);
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if (do_compare(a2, a1)) do_swap(a1, a2);
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a1->children[a1->rank++] = a2;
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a2->parent = a1;
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clean(a1);
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return a1;
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}
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void clean(group* q)
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{
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if (2 > q->rank) return;
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group* qp = q->children[q->rank-1];
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rank_type s = q->rank - 2;
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group* x = q->children[s];
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group* xp = qp->children[s];
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assert(s == x->rank);
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// If x is active, swap x and xp
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if (A[s] == x) {
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q->children[s] = xp;
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xp->parent = q;
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qp->children[s] = x;
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x->parent = qp;
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}
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}
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void pair_transform(group* a)
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{
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#if defined(BOOST_RELAXED_HEAP_DEBUG) && BOOST_RELAXED_HEAP_DEBUG > 1
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std::cerr << "- pair transform\n";
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#endif
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rank_type r = a->rank;
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// p is a's parent
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group* p = a->parent;
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assert(p != 0);
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// g is p's parent (a's grandparent)
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group* g = p->parent;
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assert(g != 0);
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// a' <- A(r)
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assert(A[r] != 0);
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group* ap = A[r];
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assert(ap != 0);
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// A(r) <- nil
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A[r] = 0;
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// let a' have parent p'
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group* pp = ap->parent;
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assert(pp != 0);
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// let a' have grandparent g'
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group* gp = pp->parent;
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assert(gp != 0);
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// Remove a and a' from their parents
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assert(ap == pp->children[pp->rank-1]); // Guaranteed because ap is active
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--pp->rank;
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// Guaranteed by caller
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assert(a == p->children[p->rank-1]);
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--p->rank;
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// Note: a, ap, p, pp all have rank r
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if (do_compare(pp, p)) {
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do_swap(a, ap);
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do_swap(p, pp);
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do_swap(g, gp);
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}
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// Assuming k(p) <= k(p')
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// make p' the rank r child of p
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assert(r == p->rank);
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p->children[p->rank++] = pp;
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pp->parent = p;
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// Combine a, ap into a rank r+1 group c
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group* c = combine(a, ap);
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// make c the rank r+1 child of g'
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assert(gp->rank > r+1);
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gp->children[r+1] = c;
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c->parent = gp;
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#if defined(BOOST_RELAXED_HEAP_DEBUG) && BOOST_RELAXED_HEAP_DEBUG > 1
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std::cerr << "After pair transform...\n";
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dump_tree();
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#endif
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if (A[r+1] == pp) A[r+1] = c;
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else promote(c);
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}
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void active_sibling_transform(group* a, group* s)
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{
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#if defined(BOOST_RELAXED_HEAP_DEBUG) && BOOST_RELAXED_HEAP_DEBUG > 1
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std::cerr << "- active sibling transform\n";
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#endif
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group* p = a->parent;
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group* g = p->parent;
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// remove a, s from their parents
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assert(s->parent == p);
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assert(p->children[p->rank-1] == s);
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--p->rank;
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assert(p->children[p->rank-1] == a);
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--p->rank;
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rank_type r = a->rank;
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A[r+1] = 0;
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a = combine(p, a);
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group* c = combine(a, s);
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// make c the rank r+2 child of g
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assert(g->children[r+2] == p);
|
|
g->children[r+2] = c;
|
|
c->parent = g;
|
|
if (A[r+2] == p) A[r+2] = c;
|
|
else promote(c);
|
|
}
|
|
|
|
void good_sibling_transform(group* a, group* s)
|
|
{
|
|
#if defined(BOOST_RELAXED_HEAP_DEBUG) && BOOST_RELAXED_HEAP_DEBUG > 1
|
|
std::cerr << "- good sibling transform\n";
|
|
#endif
|
|
rank_type r = a->rank;
|
|
group* c = s->children[s->rank-1];
|
|
assert(c->rank == r);
|
|
if (A[r] == c) {
|
|
#if defined(BOOST_RELAXED_HEAP_DEBUG) && BOOST_RELAXED_HEAP_DEBUG > 1
|
|
std::cerr << "- good sibling pair transform\n";
|
|
#endif
|
|
A[r] = 0;
|
|
group* p = a->parent;
|
|
|
|
// Remove c from its parent
|
|
--s->rank;
|
|
|
|
// Make s the rank r child of p
|
|
s->parent = p;
|
|
p->children[r] = s;
|
|
|
|
// combine a, c and let the result by the rank r+1 child of p
|
|
assert(p->rank > r+1);
|
|
group* x = combine(a, c);
|
|
x->parent = p;
|
|
p->children[r+1] = x;
|
|
|
|
if (A[r+1] == s) A[r+1] = x;
|
|
else promote(x);
|
|
|
|
#if defined(BOOST_RELAXED_HEAP_DEBUG) && BOOST_RELAXED_HEAP_DEBUG > 1
|
|
dump_tree(std::cerr);
|
|
#endif
|
|
// pair_transform(a);
|
|
} else {
|
|
// Clean operation
|
|
group* p = a->parent;
|
|
s->children[r] = a;
|
|
a->parent = s;
|
|
p->children[r] = c;
|
|
c->parent = p;
|
|
|
|
promote(a);
|
|
}
|
|
}
|
|
|
|
static void do_swap(group*& x, group*& y)
|
|
{
|
|
group* tmp = x;
|
|
x = y;
|
|
y = tmp;
|
|
}
|
|
|
|
/// Function object that compares two values in the heap
|
|
Compare compare;
|
|
|
|
/// Mapping from values to indices in the range [0, n).
|
|
ID id;
|
|
|
|
/** The root group of the queue. This group is special because it will
|
|
* never store a value, but it acts as a parent to all of the
|
|
* roots. Thus, its list of children is the list of roots.
|
|
*/
|
|
group root;
|
|
|
|
/** Mapping from the group index of a value to the group associated
|
|
* with that value. If a value is not in the queue, then the "value"
|
|
* field will be empty.
|
|
*/
|
|
std::vector<group> index_to_group;
|
|
|
|
/** Flat data structure containing the values in each of the
|
|
* groups. It will be indexed via the id of the values. The groups
|
|
* are each log_n long, with the last group potentially being
|
|
* smaller.
|
|
*/
|
|
std::vector< ::boost::optional<value_type> > groups;
|
|
|
|
/** The list of active groups, indexed by rank. When A[r] is null,
|
|
* there is no active group of rank r. Otherwise, A[r] is the active
|
|
* group of rank r.
|
|
*/
|
|
std::vector<group*> A;
|
|
|
|
/** The group containing the smallest value in the queue, which must
|
|
* be either a root or an active group. If this group is null, then we
|
|
* will need to search for this group when it is needed.
|
|
*/
|
|
mutable group* smallest_value;
|
|
|
|
/// Cached value log_base_2(n)
|
|
size_type log_n;
|
|
};
|
|
|
|
|
|
} // end namespace boost
|
|
|
|
#if defined(BOOST_MSVC)
|
|
# pragma warning(pop)
|
|
#endif
|
|
|
|
#endif // BOOST_RELAXED_HEAP_HEADER
|