turbonss/cxxmph/mph_map.h

#ifndef __CXXMPH_MPH_MAP_H__
#define __CXXMPH_MPH_MAP_H__
// Implementation of the unordered associative mapping interface using a
// minimal perfect hash function.
//
// This class is about 20% to 100% slower than unordered_map (or ext/hash_map)
// and should not be used if performance is a concern. In fact, you should only
// use it for educational purposes.
//
// See http://www.strchr.com/crc32_popcnt and new Murmur3 function to try to beat stl

#include <algorithm>
#include <iostream>
#include <limits>
#include <unordered_map>
#include <unordered_set>
#include <vector>
#include <utility>  // for std::pair

#include "mph_bits.h"
#include "mph_index.h"
#include "hollow_iterator.h"

namespace cxxmph {

using std::pair;
using std::make_pair;
using std::unordered_map;
using std::vector;

// Save on repetitive typing.
#define MPH_MAP_TMPL_SPEC template <class Key, class Data, class HashFcn, class EqualKey, class Alloc>
#define MPH_MAP_CLASS_SPEC mph_map<Key, Data, HashFcn, EqualKey, Alloc>
#define MPH_MAP_METHOD_DECL(r, m) MPH_MAP_TMPL_SPEC typename MPH_MAP_CLASS_SPEC::r MPH_MAP_CLASS_SPEC::m

template <class Key, class Data, class HashFcn = std::hash<Key>, class EqualKey = std::equal_to<Key>, class Alloc = std::allocator<Data> >
class mph_map {
 public:
  typedef Key key_type;
  typedef Data data_type;
  typedef pair<Key, Data> value_type;
  typedef HashFcn hasher;
  typedef EqualKey key_equal;

  typedef typename std::vector<value_type>::pointer pointer;
  typedef typename std::vector<value_type>::reference reference;
  typedef typename std::vector<value_type>::const_reference const_reference;
  typedef typename std::vector<value_type>::size_type size_type;
  typedef typename std::vector<value_type>::difference_type difference_type;

  typedef hollow_iterator<std::vector<value_type>> iterator;
  typedef hollow_const_iterator<std::vector<value_type>> const_iterator;

  // For making macros simpler.
  typedef void void_type;
  typedef bool bool_type;
  typedef pair<iterator, bool> insert_return_type;

  mph_map();
  ~mph_map();

  iterator begin();
  iterator end();
  const_iterator begin() const;
  const_iterator end() const;
  size_type size() const;
  bool empty() const;
  void clear();
  void erase(iterator pos);
  void erase(const key_type& k);
  pair<iterator, bool> insert(const value_type& x);
  iterator find(const key_type& k) { return slow_find(k, index_.perfect_hash(k)); }
  const_iterator find(const key_type& k) const { return slow_find(k, index_.perfect_hash(k)); };
  typedef int32_t my_int32_t;  // help macros
  int32_t index(const key_type& k) const;
  data_type& operator[](const key_type &k);
  const data_type& operator[](const key_type &k) const;

  size_type bucket_count() const { return index_.perfect_hash_size() + slack_.bucket_count(); }
  void rehash(size_type nbuckets /*ignored*/); 

 protected:  // mimicking STL implementation
  EqualKey equal_;

 private:
   template <typename iterator>
   struct iterator_first : public iterator {
     iterator_first(iterator it) : iterator(it) { }
     const typename iterator::value_type::first_type& operator*() {
      return this->iterator::operator*().first;
     }
   };

   template <typename iterator>
     iterator_first<iterator> make_iterator_first(iterator it) {
     return iterator_first<iterator>(it);
   }

   iterator make_iterator(typename std::vector<value_type>::iterator it) {
     return hollow_iterator<std::vector<value_type>>(&values_, &present_, it);
   }
   const_iterator make_iterator(typename std::vector<value_type>::const_iterator it) const {
     return hollow_const_iterator<std::vector<value_type>>(&values_, &present_, it);
   }

   // Experimental functions, not always faster
   iterator fast_find(const key_type& k);
   const_iterator fast_find(const key_type& k) const;
   iterator slow_find(const key_type& k, uint32_t perfect_hash);
   const_iterator slow_find(const key_type& k, uint32_t perfect_hash) const;
   static const uint8_t kNestCollision = 3;  // biggest 2 bit value
   void set_nest_value(const uint32_t* h, uint8_t value) {
     auto index = get_nest_index(h);
     assert(get_nest_index(h) < nests_.size());
     assert(get_nest_index(h) >> 2 < nests_.size());
     assert(value < 4);
     nests_.set(index, value);
     assert(nests_[index] == value);
   }
   uint32_t get_nest_value(const uint32_t* h) const {
     assert(get_nest_index(h) < nests_.size());
     return nests_[get_nest_index(h)];
   }
   uint32_t get_nest_index(const uint32_t* h) const {
     assert(nests_.size());
     assert(nests_.size() % 2 == 0);
     assert((nests_.size() & (nests_.size() - 1)) == 0);
     assert((h[3] % nests_.size()) == (h[3] & (nests_.size() - 1)));
     return (h[3] & (nests_.size() - 1));  // a mod 2^n == a & 2^n - 1
   }

   void pack();
   std::vector<value_type> values_;
   std::vector<bool> present_;
   dynamic_2bitset nests_;
   SimpleMPHIndex<Key, typename seeded_hash<HashFcn>::hash_function> index_;
   // TODO(davi) optimize slack to hold 128 unique bits from hash64 as key
   typedef unordered_map<Key, uint32_t, HashFcn, EqualKey, Alloc> slack_type;
   slack_type slack_;
   size_type size_;

   mutable uint64_t fast_;
   mutable uint64_t fast_taken_;
   mutable uint64_t slow_;
   mutable uint64_t very_slow_;
};

MPH_MAP_TMPL_SPEC
bool operator==(const MPH_MAP_CLASS_SPEC& lhs, const MPH_MAP_CLASS_SPEC& rhs) {
  return lhs.size() == rhs.size() && std::equal(lhs.begin(), lhs.end(), rhs.begin());
}

MPH_MAP_TMPL_SPEC MPH_MAP_CLASS_SPEC::mph_map() : size_(0) {
  clear();
  pack();
}

MPH_MAP_TMPL_SPEC MPH_MAP_CLASS_SPEC::~mph_map() {
  // fprintf(stderr, "Fast taken: %d Fast: %d Slow %d very_slow %d ratio %f\n", fast_taken_, fast_, slow_, very_slow_, fast_*1.0/slow_);
}

MPH_MAP_METHOD_DECL(insert_return_type, insert)(const value_type& x) {
  auto it = find(x.first);
  auto it_end = end();
  if (it != it_end) return make_pair(it, false);
  bool should_pack = false;
  if (values_.capacity() == values_.size() && values_.size() > 256) {
    should_pack = true;
  }
  values_.push_back(x);
  present_.push_back(true);
  uint32_t h[4];
  index_.hash_vector(x.first, h);
  set_nest_value(h, kNestCollision);
  ++size_;
  slack_.insert(make_pair(x.first, values_.size() - 1));
  if (should_pack) pack();
  it = find(x.first);
  slow_ = 0;
  very_slow_ = 0;
  fast_ = 0;
  fast_taken_ = 0;
  return make_pair(it, true);
}

MPH_MAP_METHOD_DECL(void_type, pack)() {
  // fprintf(stderr, "Paki %d values\n", values_.size());
  if (values_.empty()) return;
  assert(std::unordered_set<key_type>(make_iterator_first(begin()), make_iterator_first(end())).size() == size());
  bool success = index_.Reset(
      make_iterator_first(begin()),
      make_iterator_first(end()), size_);
  assert(success);
  std::vector<value_type> new_values(index_.perfect_hash_size());
  new_values.reserve(new_values.size() * 2);
  std::vector<bool> new_present(index_.perfect_hash_size(), false);
  new_present.reserve(new_present.size() * 2);
  auto new_nests_size = nextpoweroftwo(ceil(new_values.size())*10000 + 1);
  dynamic_2bitset(new_nests_size, true /* fill with 1s */).swap(nests_);
  vector<bool> used_nests(nests_.size());
  uint32_t collisions = 0;
  for (iterator it = begin(), it_end = end(); it != it_end; ++it) {
    size_type id = index_.perfect_hash(it->first);
    assert(id < new_values.size());
    new_values[id] = *it;
    new_present[id] = true;
    uint32_t h[4];
    index_.hash_vector(it->first, h);
    // fprintf(stderr, "Nest index: %d\n", get_nest_index(h));
    assert(used_nests.size() > get_nest_index(h));
    if (used_nests[get_nest_index(h)]) {
      set_nest_value(h, kNestCollision);
      assert(get_nest_value(h) == kNestCollision); 
      // fprintf(stderr, "Collision at nest index %d among %d positions\n", get_nest_index(h), nests_.size());
      ++collisions;
    } else {
      set_nest_value(h, index_.cuckoo_nest(h));
      assert(get_nest_value(h) == index_.cuckoo_nest(h)); 
      assert(index_.perfect_hash(it->first) == index_.cuckoo_hash(h, get_nest_value(h))); 
      used_nests[get_nest_index(h)] = true;
    }
  }
  // fprintf(stderr, "Collision ratio: %f\n", collisions*1.0/size());
  values_.swap(new_values);
  present_.swap(new_present);
  slack_type().swap(slack_);
  int32_t fast = 0;
  int32_t slow= 0;
  for (iterator it = begin(), it_end = end(); it != it_end; ++it) {
    uint32_t h[4];
    index_.hash_vector(it->first, h);
    if (get_nest_value(h) == kNestCollision) ++slow;
    else {
      ++fast;
      auto cit = values_.begin() + index_.cuckoo_hash(h, get_nest_value(h));
      assert(index_.perfect_hash(it->first) == cit - values_.begin());
      assert(equal_(it->first, cit->first));
    } 
  }
  // fprintf(stderr, "Predicted fast: %d slow %d\n", fast, slow);
}

MPH_MAP_METHOD_DECL(iterator, begin)() { return make_iterator(values_.begin()); }
MPH_MAP_METHOD_DECL(iterator, end)() { return make_iterator(values_.end()); }
MPH_MAP_METHOD_DECL(const_iterator, begin)() const { return make_iterator(values_.begin()); }
MPH_MAP_METHOD_DECL(const_iterator, end)() const { return make_iterator(values_.end()); }
MPH_MAP_METHOD_DECL(bool_type, empty)() const { return size_ == 0; }
MPH_MAP_METHOD_DECL(size_type, size)() const { return size_; }

MPH_MAP_METHOD_DECL(void_type, clear)() {
  values_.clear();
  present_.clear();
  slack_.clear();
  index_.clear();
  dynamic_2bitset(8, true /* fill with 1s */).swap(nests_);
  size_ = 0;
}

MPH_MAP_METHOD_DECL(void_type, erase)(iterator pos) {
  present_[pos - begin] = false;
  uint32_t h[4];
  index_.hash_vector(pos->first, &h);
  nests_[get_nest_index(h)] = kNestCollision;
  *pos = value_type();
  --size_;
}
MPH_MAP_METHOD_DECL(void_type, erase)(const key_type& k) {
  iterator it = find(k);
  if (it == end()) return;
  erase(it);
}

MPH_MAP_METHOD_DECL(const_iterator, fast_find)(const key_type& k) const {
  uint32_t h[4];
  index_.hash_vector(k, h);
  auto nest = get_nest_value(h);
  if (__builtin_expect(nest != kNestCollision, 1)) {
    ++fast_taken_;
    auto vit = values_.begin() + index_.cuckoo_hash(h, nest);
    // do not hold for unknown keys
    assert(values_.size() != index_.perfect_hash_size() || equal_(k, vit->first));
    if (equal_(k, vit->first)) {
      ++fast_;
      return make_iterator(vit);
    }
  }
  nest = index_.cuckoo_nest(h);
  ++slow_;
  return slow_find(k, index_.cuckoo_hash(h, nest));
}

MPH_MAP_METHOD_DECL(const_iterator, slow_find)(const key_type& k, uint32_t perfect_hash) const {
  if (__builtin_expect(index_.perfect_hash_size(), 1)) {
    if (__builtin_expect(present_[perfect_hash], true)) { 
      auto vit = values_.begin() + perfect_hash;
      if (equal_(k, vit->first)) return make_iterator(vit);
    }
  }
  if (__builtin_expect(!slack_.empty(), 0)) {
     ++very_slow_;
     auto sit = slack_.find(k);
     if (sit != slack_.end()) return make_iterator(values_.begin() + sit->second);
  }
  return end();
}

MPH_MAP_METHOD_DECL(iterator, fast_find)(const key_type& k) {
  uint32_t h[4];
  index_.hash_vector(k, h);
  auto nest = get_nest_value(h);
  if (__builtin_expect(nest != kNestCollision, 1)) {
    ++fast_taken_;
    auto vit = values_.begin() + index_.cuckoo_hash(h, nest);
    assert(values_.size() != index_.perfect_hash_size() || equal_(k, vit->first));
    if (equal_(k, vit->first)) {
      ++fast_;
      return make_iterator(vit);
    }
  }
  nest = index_.cuckoo_nest(h);
  ++slow_;
  return slow_find(k, index_.cuckoo_hash(h, nest));
}

MPH_MAP_METHOD_DECL(iterator, slow_find)(const key_type& k, uint32_t perfect_hash) {
  if (__builtin_expect(index_.perfect_hash_size(), 1)) {
    if (__builtin_expect(present_[perfect_hash], true)) { 
      auto vit = values_.begin() + perfect_hash;
      if (equal_(k, vit->first)) return make_iterator(vit);
    }
  }
  if (__builtin_expect(!slack_.empty(), 0)) {
     ++very_slow_;
     auto sit = slack_.find(k);
     if (sit != slack_.end()) return make_iterator(values_.begin() + sit->second);
  }
  return end();
}

MPH_MAP_METHOD_DECL(my_int32_t, index)(const key_type& k) const {
  if (index_.size() == 0) return -1;
  return index_.perfect_hash(k);
}

MPH_MAP_METHOD_DECL(data_type&, operator[])(const key_type& k) {
  return insert(make_pair(k, data_type())).first->second;
}
MPH_MAP_METHOD_DECL(void_type, rehash)(size_type nbuckets) {
  pack();
  vector<value_type>(values_.begin(), values_.end()).swap(values_);
  vector<bool>(present_.begin(), present_.end()).swap(present_);
  slack_type().swap(slack_);
}


}  // namespace cxxmph

#endif  // __CXXMPH_MPH_MAP_H__