241 lines
8.2 KiB
C++
241 lines
8.2 KiB
C++
#ifndef __CXXMPH_MPH_MAP_H__
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#define __CXXMPH_MPH_MAP_H__
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// Implementation of the unordered associative mapping interface using a
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// minimal perfect hash function.
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//
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// This class not necessarily faster than unordered_map (or ext/hash_map).
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// Benchmark your code before using it. If you do not call rehash() before
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// starting your reads, it will be definitively slower than unordered_map.
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//
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// For large sets of urls, which are a somewhat expensive to compare, I found
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// this class to be about 10% faster than unordered_map.
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//
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// The space overhead of this map is 1.93 bits per bucket and it achieves 100%
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// occupation with a rehash call.
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#include <algorithm>
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#include <iostream>
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#include <limits>
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#include <unordered_map>
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#include <unordered_set>
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#include <vector>
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#include <utility> // for std::pair
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#include "mph_bits.h"
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#include "mph_index.h"
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#include "hollow_iterator.h"
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namespace cxxmph {
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using std::pair;
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using std::make_pair;
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using std::unordered_map;
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using std::vector;
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// Save on repetitive typing.
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#define MPH_MAP_TMPL_SPEC template <class Key, class Data, class HashFcn, class EqualKey, class Alloc>
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#define MPH_MAP_CLASS_SPEC mph_map<Key, Data, HashFcn, EqualKey, Alloc>
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#define MPH_MAP_METHOD_DECL(r, m) MPH_MAP_TMPL_SPEC typename MPH_MAP_CLASS_SPEC::r MPH_MAP_CLASS_SPEC::m
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#define MPH_MAP_INLINE_METHOD_DECL(r, m) MPH_MAP_TMPL_SPEC inline typename MPH_MAP_CLASS_SPEC::r MPH_MAP_CLASS_SPEC::m
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template <class Key, class Data, class HashFcn = std::hash<Key>, class EqualKey = std::equal_to<Key>, class Alloc = std::allocator<Data> >
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class mph_map {
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public:
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typedef Key key_type;
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typedef Data data_type;
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typedef pair<Key, Data> value_type;
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typedef HashFcn hasher;
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typedef EqualKey key_equal;
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typedef typename vector<value_type>::pointer pointer;
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typedef typename vector<value_type>::reference reference;
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typedef typename vector<value_type>::const_reference const_reference;
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typedef typename vector<value_type>::size_type size_type;
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typedef typename vector<value_type>::difference_type difference_type;
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typedef is_empty<const vector<value_type>> is_empty_type;
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typedef hollow_iterator_base<typename vector<value_type>::iterator, is_empty_type> iterator;
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typedef hollow_iterator_base<typename vector<value_type>::const_iterator, is_empty_type> const_iterator;
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// For making macros simpler.
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typedef void void_type;
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typedef bool bool_type;
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typedef pair<iterator, bool> insert_return_type;
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mph_map();
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~mph_map();
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iterator begin();
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iterator end();
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const_iterator begin() const;
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const_iterator end() const;
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size_type size() const;
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bool empty() const;
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void clear();
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void erase(iterator pos);
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void erase(const key_type& k);
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pair<iterator, bool> insert(const value_type& x);
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inline iterator find(const key_type& k);
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inline const_iterator find(const key_type& k) const;
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typedef int32_t my_int32_t; // help macros
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inline int32_t index(const key_type& k) const;
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data_type& operator[](const key_type &k);
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const data_type& operator[](const key_type &k) const;
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size_type bucket_count() const { return index_.perfect_hash_size() + slack_.bucket_count(); }
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void rehash(size_type nbuckets /*ignored*/);
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protected: // mimicking STL implementation
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EqualKey equal_;
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private:
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template <typename iterator>
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struct iterator_first : public iterator {
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iterator_first(iterator it) : iterator(it) { }
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const typename iterator::value_type::first_type& operator*() {
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return this->iterator::operator*().first;
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}
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};
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template <typename iterator>
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iterator_first<iterator> make_iterator_first(iterator it) {
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return iterator_first<iterator>(it);
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}
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void pack();
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vector<value_type> values_;
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vector<bool> present_;
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SimpleMPHIndex<Key, typename seeded_hash<HashFcn>::hash_function> index_;
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// TODO(davi) optimize slack to use hash from index rather than calculate its own
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typedef unordered_map<h128, uint32_t, h128::hash32> slack_type;
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slack_type slack_;
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size_type size_;
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typename seeded_hash<HashFcn>::hash_function hasher128_;
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};
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MPH_MAP_TMPL_SPEC
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bool operator==(const MPH_MAP_CLASS_SPEC& lhs, const MPH_MAP_CLASS_SPEC& rhs) {
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return lhs.size() == rhs.size() && std::equal(lhs.begin(), lhs.end(), rhs.begin());
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}
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MPH_MAP_TMPL_SPEC MPH_MAP_CLASS_SPEC::mph_map() : size_(0) {
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clear();
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pack();
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}
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MPH_MAP_TMPL_SPEC MPH_MAP_CLASS_SPEC::~mph_map() {
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}
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MPH_MAP_METHOD_DECL(insert_return_type, insert)(const value_type& x) {
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auto it = find(x.first);
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auto it_end = end();
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if (it != it_end) return make_pair(it, false);
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bool should_pack = false;
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if (values_.capacity() == values_.size() && values_.size() > 256) {
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should_pack = true;
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}
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values_.push_back(x);
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present_.push_back(true);
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++size_;
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h128 h = hasher128_.hash128(x.first, 0);
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if (slack_.find(h) != slack_.end()) should_pack = true; // unavoidable pack
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else slack_.insert(std::make_pair(h, values_.size() - 1));
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if (should_pack) pack();
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it = find(x.first);
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return make_pair(it, true);
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}
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MPH_MAP_METHOD_DECL(void_type, pack)() {
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// fprintf(stderr, "Paki %d values\n", values_.size());
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if (values_.empty()) return;
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assert(std::unordered_set<key_type>(make_iterator_first(begin()), make_iterator_first(end())).size() == size());
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bool success = index_.Reset(
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make_iterator_first(begin()),
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make_iterator_first(end()), size_);
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if (!success) { exit(-1); }
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vector<value_type> new_values(index_.perfect_hash_size());
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new_values.reserve(new_values.size() * 2);
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vector<bool> new_present(index_.perfect_hash_size(), false);
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new_present.reserve(new_present.size() * 2);
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for (iterator it = begin(), it_end = end(); it != it_end; ++it) {
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size_type id = index_.perfect_hash(it->first);
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assert(id < index_.perfect_hash_size());
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assert(id < new_values.size());
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new_values[id] = *it;
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new_present[id] = true;
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}
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// fprintf(stderr, "Collision ratio: %f\n", collisions*1.0/size());
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values_.swap(new_values);
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present_.swap(new_present);
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slack_type().swap(slack_);
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}
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MPH_MAP_METHOD_DECL(iterator, begin)() { return make_hollow(&values_, &present_, values_.begin()); }
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MPH_MAP_METHOD_DECL(iterator, end)() { return make_solid(&values_, &present_, values_.end()); }
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MPH_MAP_METHOD_DECL(const_iterator, begin)() const { return make_hollow(&values_, &present_, values_.begin()); }
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MPH_MAP_METHOD_DECL(const_iterator, end)() const { return make_solid(&values_, &present_, values_.end()); }
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MPH_MAP_METHOD_DECL(bool_type, empty)() const { return size_ == 0; }
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MPH_MAP_METHOD_DECL(size_type, size)() const { return size_; }
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MPH_MAP_METHOD_DECL(void_type, clear)() {
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values_.clear();
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present_.clear();
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slack_.clear();
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index_.clear();
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size_ = 0;
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}
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MPH_MAP_METHOD_DECL(void_type, erase)(iterator pos) {
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present_[pos.it_ - begin().it_] = false;
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*pos = value_type();
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--size_;
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}
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MPH_MAP_METHOD_DECL(void_type, erase)(const key_type& k) {
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iterator it = find(k);
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if (it == end()) return;
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erase(it);
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}
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MPH_MAP_INLINE_METHOD_DECL(const_iterator, find)(const key_type& k) const {
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auto idx = index(k);
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typename vector<value_type>::const_iterator vit = values_.begin() + idx;
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if (idx == -1 || vit->first != k) return end();
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return make_solid(&values_, &present_, vit);;
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}
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MPH_MAP_INLINE_METHOD_DECL(iterator, find)(const key_type& k) {
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auto idx = index(k);
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typename vector<value_type>::iterator vit = values_.begin() + idx;
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if (idx == -1 || vit->first != k) return end();
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return make_solid(&values_, &present_, vit);;
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}
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MPH_MAP_INLINE_METHOD_DECL(my_int32_t, index)(const key_type& k) const {
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if (__builtin_expect(!slack_.empty(), 0)) {
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auto sit = slack_.find(hasher128_.hash128(k, 0));
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if (sit != slack_.end()) return sit->second;
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}
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if (__builtin_expect(index_.perfect_hash_size(), 1)) {
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auto perfect_hash = index_.perfect_hash(k);
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if (__builtin_expect(present_[perfect_hash], true)) {
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return perfect_hash;
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}
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}
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return -1;
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}
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MPH_MAP_METHOD_DECL(data_type&, operator[])(const key_type& k) {
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return insert(make_pair(k, data_type())).first->second;
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}
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MPH_MAP_METHOD_DECL(void_type, rehash)(size_type nbuckets) {
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pack();
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vector<value_type>(values_.begin(), values_.end()).swap(values_);
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vector<bool>(present_.begin(), present_.end()).swap(present_);
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slack_type().swap(slack_);
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}
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} // namespace cxxmph
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#endif // __CXXMPH_MPH_MAP_H__
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