331 lines
11 KiB
C++
331 lines
11 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 is about 20% to 100% slower than unordered_map (or ext/hash_map)
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// and should not be used if performance is a concern. In fact, you should only
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// use it for educational purposes.
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//
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// See http://www.strchr.com/crc32_popcnt and new Murmur3 function to try to beat stl
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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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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 std::vector<value_type>::pointer pointer;
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typedef typename std::vector<value_type>::reference reference;
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typedef typename std::vector<value_type>::const_reference const_reference;
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typedef typename std::vector<value_type>::size_type size_type;
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typedef typename std::vector<value_type>::difference_type difference_type;
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typedef hollow_iterator<std::vector<value_type>> iterator;
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typedef hollow_const_iterator<std::vector<value_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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iterator find(const key_type& k);
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const_iterator find(const key_type& k) const;
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typedef int32_t my_int32_t; // help macros
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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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iterator make_iterator(typename std::vector<value_type>::iterator it) {
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return hollow_iterator<std::vector<value_type>>(&values_, &present_, it);
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}
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const_iterator make_iterator(typename std::vector<value_type>::const_iterator it) const {
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return hollow_const_iterator<std::vector<value_type>>(&values_, &present_, it);
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}
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iterator slow_find(const key_type& k, uint32_t perfect_hash);
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const_iterator slow_find(const key_type& k, uint32_t perfect_hash) const;
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static const uint8_t kNestCollision = 3; // biggest 2 bit value
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void set_nest_value(const uint32_t* h, uint8_t value) {
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auto index = get_nest_index(h);
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assert(get_nest_index(h) < nests_.size());
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assert(get_nest_index(h) >> 2 < nests_.size());
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assert(value < 4);
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nests_.set(index, value);
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assert(nests_[index] == value);
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}
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uint32_t get_nest_value(const uint32_t* h) const {
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assert(get_nest_index(h) < nests_.size());
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return nests_[get_nest_index(h)];
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}
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uint32_t get_nest_index(const uint32_t* h) const {
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assert(nests_.size());
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return h[3] % nests_.size(); // a mod 2^n == a & 2^n - 1
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// return h[3] & (nests_.size() - 1); // a mod 2^n == a & 2^n - 1
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}
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void pack();
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std::vector<value_type> values_;
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std::vector<bool> present_;
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dynamic_2bitset nests_;
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SimpleMPHIndex<Key, typename seeded_hash<HashFcn>::hash_function> index_;
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// TODO(davi) optimize slack to hold 128 unique bits from hash64 as key
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typedef unordered_map<Key, uint32_t, HashFcn, EqualKey, Alloc> slack_type;
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slack_type slack_;
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size_type size_;
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mutable uint64_t fast_;
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mutable uint64_t slow_;
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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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fprintf(stderr, "Fast: %d Slow %d ratio %f\n", fast_, slow_, fast_*1.0/slow_);
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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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uint32_t h[4];
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index_.hash_vector(x.first, h);
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set_nest_value(h, kNestCollision);
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++size_;
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slack_.insert(make_pair(x.first, 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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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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assert(success);
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std::vector<value_type> new_values(index_.perfect_hash_size());
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new_values.reserve(new_values.size() * 2);
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std::vector<bool> new_present(index_.perfect_hash_size(), false);
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new_present.reserve(new_present.size() * 2);
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auto new_nests_size = nextpoweroftwo(ceil(new_values.size())*10 + 1);
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dynamic_2bitset(new_nests_size, true /* fill with 1s */).swap(nests_);
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vector<bool> used_nests(nests_.size());
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uint32_t collisions = 0;
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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 < new_values.size());
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new_values[id] = *it;
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new_present[id] = true;
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uint32_t h[4];
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index_.hash_vector(it->first, h);
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// fprintf(stderr, "Nest index: %d\n", get_nest_index(h));
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assert(used_nests.size() > get_nest_index(h));
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if (used_nests[get_nest_index(h)]) {
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set_nest_value(h, kNestCollision);
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assert(get_nest_value(h) == kNestCollision);
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// fprintf(stderr, "Collision at nest index %d among %d positions\n", get_nest_index(h), nests_.size());
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++collisions;
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} else {
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set_nest_value(h, index_.cuckoo_nest(h));
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assert(get_nest_value(h) == index_.cuckoo_nest(h));
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assert(index_.perfect_hash(it->first) == index_.cuckoo_hash(h, get_nest_value(h)));
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used_nests[get_nest_index(h)] = true;
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}
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}
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for (iterator it = begin(), it_end = end(); it != it_end; ++it) {
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uint32_t h[4];
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index_.hash_vector(it->first, h);
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assert(get_nest_value(h) == kNestCollision || index_.perfect_hash(it->first) == index_.cuckoo_hash(h, get_nest_value(h)));
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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_iterator(values_.begin()); }
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MPH_MAP_METHOD_DECL(iterator, end)() { return make_iterator(values_.end()); }
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MPH_MAP_METHOD_DECL(const_iterator, begin)() const { return make_iterator(values_.begin()); }
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MPH_MAP_METHOD_DECL(const_iterator, end)() const { return make_iterator(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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dynamic_2bitset(1, true /* fill with 1s */).swap(nests_);
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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 - begin] = false;
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uint32_t h[4];
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index_.hash_vector(pos->first, &h);
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nests_[get_nest_index(h)] = kNestCollision;
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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_METHOD_DECL(const_iterator, find)(const key_type& k) const {
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uint32_t h[4];
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index_.hash_vector(k, h);
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auto nest = get_nest_value(h);
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if (__builtin_expect(nest != kNestCollision, 1)) {
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auto vit = values_.begin() + index_.cuckoo_hash(h, nest);
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if (equal_(k, vit->first)) {
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++fast_;
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return make_iterator(vit);
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}
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}
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nest = index_.cuckoo_nest(h);
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++slow_;
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return slow_find(k, index_.cuckoo_hash(h, nest));
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}
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MPH_MAP_METHOD_DECL(const_iterator, slow_find)(const key_type& k, uint32_t perfect_hash) const {
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if (__builtin_expect(index_.perfect_hash_size(), 0)) {
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if (__builtin_expect(present_[perfect_hash], true)) {
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auto vit = values_.begin() + perfect_hash;
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if (equal_(k, vit->first)) return make_iterator(vit);
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}
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}
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if (__builtin_expect(!slack_.empty(), 0)) {
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auto sit = slack_.find(k);
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if (sit != slack_.end()) return make_iterator(values_.begin() + sit->second);
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}
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return end();
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}
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MPH_MAP_METHOD_DECL(iterator, find)(const key_type& k) {
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uint32_t h[4];
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index_.hash_vector(k, h);
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auto nest = get_nest_value(h);
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if (__builtin_expect(nest != kNestCollision, 1)) {
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auto vit = values_.begin() + index_.cuckoo_hash(h, nest);
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if (equal_(k, vit->first)) {
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++fast_;
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return make_iterator(vit);
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}
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}
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nest = index_.cuckoo_nest(h);
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++slow_;
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return slow_find(k, index_.cuckoo_hash(h, nest));
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}
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MPH_MAP_METHOD_DECL(iterator, slow_find)(const key_type& k, uint32_t perfect_hash) {
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if (__builtin_expect(index_.perfect_hash_size(), 0)) {
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if (__builtin_expect(present_[perfect_hash], true)) {
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auto vit = values_.begin() + perfect_hash;
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if (equal_(k, vit->first)) return make_iterator(vit);
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}
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}
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if (__builtin_expect(!slack_.empty(), 0)) {
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auto sit = slack_.find(k);
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if (sit != slack_.end()) return make_iterator(values_.begin() + sit->second);
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}
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return end();
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}
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MPH_MAP_METHOD_DECL(my_int32_t, index)(const key_type& k) const {
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if (index_.size() == 0) return -1;
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return index_.perfect_hash(k);
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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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