Finally beat STL. Trying improvement around cuckoo hashing idea.
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@ -49,6 +49,7 @@ class BM_SearchUrls : public SearchUrlsBenchmark {
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mymap_[*it] = *it;
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}
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mymap_.rehash(mymap_.bucket_count());
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fprintf(stderr, "Occupation: %f\n", static_cast<float>(mymap_.size())/mymap_.bucket_count());
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return true;
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}
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MapType mymap_;
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@ -57,7 +58,7 @@ class BM_SearchUrls : public SearchUrlsBenchmark {
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template <class MapType>
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class BM_SearchUint64 : public SearchUint64Benchmark {
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public:
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BM_SearchUint64() : SearchUint64Benchmark(10000, 10*1000*1000) { }
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BM_SearchUint64() : SearchUint64Benchmark(100000, 10*1000*1000) { }
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virtual bool SetUp() {
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if (!SearchUint64Benchmark::SetUp()) return false;
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for (int i = 0; i < values_.size(); ++i) {
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@ -88,15 +89,13 @@ using namespace cxxmph;
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int main(int argc, char** argv) {
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srandom(4);
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/*
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Benchmark::Register(new BM_CreateUrls<mph_map<StringPiece, StringPiece>>("URLS100k"));
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Benchmark::Register(new BM_CreateUrls<unordered_map<StringPiece, StringPiece>>("URLS100k"));
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Benchmark::Register(new BM_SearchUrls<mph_map<StringPiece, StringPiece>>("URLS100k", 10*1000 * 1000, 0));
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Benchmark::Register(new BM_SearchUrls<unordered_map<StringPiece, StringPiece, Murmur3StringPiece>>("URLS100k", 10*1000 * 1000, 0));
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Benchmark::Register(new BM_SearchUrls<mph_map<StringPiece, StringPiece>>("URLS100k", 10*1000 * 1000, 0.9));
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Benchmark::Register(new BM_SearchUrls<unordered_map<StringPiece, StringPiece, Murmur3StringPiece>>("URLS100k", 10*1000 * 1000, 0.9));
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*/
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Benchmark::Register(new BM_SearchUint64<unordered_map<uint64_t, uint64_t>>);
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Benchmark::Register(new BM_SearchUint64<mph_map<uint64_t, uint64_t>>);
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Benchmark::Register(new BM_SearchUint64<unordered_map<uint64_t, uint64_t>>);
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Benchmark::RunAll();
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}
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@ -25,6 +25,7 @@
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#include <stdint.h>
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#include <cassert>
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#include <climits>
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#include <cmath>
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#include <unordered_map> // for std::hash
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#include <vector>
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@ -63,6 +64,12 @@ class MPHIndex {
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template <class SeededHashFcn, class Key> // must agree with Reset
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uint32_t minimal_perfect_hash(const Key& x) const;
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// Crazy functions. Ignore.
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template <class SeededHashFcn, class Key> // must agree with Reset
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uint32_t cuckoo_hash(const Key& x, const uint32_t* h, uint8_t nest) const;
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template <class SeededHashFcn, class Key> // must agree with Reset
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void hash_vector(const Key& x, uint32_t* h) const;
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// Serialization for mmap usage - not tested well, ping me if you care.
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// Serialized tables are not guaranteed to work across versions or different
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// endianness (although they could easily be made to be).
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@ -94,6 +101,8 @@ class MPHIndex {
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// Partition vertex count, derived from c parameter.
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uint32_t r_;
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uint32_t nest_displacement_[3]; // derived from r_
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// The array containing the minimal perfect hash function graph. Do not use
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// c++ vector to make mmap based backing easier.
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const uint8_t* g_;
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@ -118,6 +127,16 @@ class MPHIndex {
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};
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template <class T>
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T nexthigher(T k) {
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if (k == 0)
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return 1;
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k--;
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for (int i=1; i<sizeof(T)*CHAR_BIT; i<<=1)
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k = k | k >> i;
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return k+1;
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}
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// Template method needs to go in the header file.
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template <class SeededHashFcn, class ForwardIterator>
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bool MPHIndex::Reset(
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@ -129,6 +148,13 @@ bool MPHIndex::Reset(
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m_ = size;
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r_ = static_cast<uint32_t>(ceil((c_*m_)/3));
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if ((r_ % 2) == 0) r_ += 1;
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nest_displacement_[0] = 0;
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nest_displacement_[1] = r_;
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nest_displacement_[2] = (r_ << 1);
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// This can be used to speed mods, but increases occupation too much.
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// Needs to try http://gmplib.org/manual/Integer-Exponentiation.html instead
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// r_ = nexthigher(r_);
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n_ = 3*r_;
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k_ = 1U << b_;
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@ -174,15 +200,24 @@ bool MPHIndex::Mapping(
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return false;
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}
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template <class SeededHashFcn, class Key>
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uint32_t MPHIndex::cuckoo_hash(const Key& key, const uint32_t* h, uint8_t nest) const {
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return (h[nest] % r_) + nest_displacement_[nest];
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}
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template <class SeededHashFcn, class Key>
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void MPHIndex::hash_vector(const Key& key, uint32_t* h) const {
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SeededHashFcn().hash64(key, hash_seed_[0], reinterpret_cast<uint32_t*>(&h));
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}
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template <class SeededHashFcn, class Key>
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uint32_t MPHIndex::perfect_hash(const Key& key) const {
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uint32_t h[4];
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SeededHashFcn().hash64(key, hash_seed_[0], reinterpret_cast<uint32_t*>(&h));
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// for (int i = 0; i < 3; ++i) h[i] = SeededHashFcn()(key, hash_seed_[i]);
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assert(r_);
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h[0] = h[0] % r_;
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h[1] = h[1] % r_ + r_;
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h[2] = h[2] % r_ + (r_ << 1);
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h[0] = (h[0] % r_) + nest_displacement_[0];
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h[1] = (h[1] % r_) + nest_displacement_[1];
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h[2] = (h[2] % r_) + nest_displacement_[2];
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assert(g_size_);
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// cerr << "g_.size() " << g_size_ << " h0 >> 2 " << (h[0] >> 2) << endl;
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assert((h[0] >> 2) <g_size_);
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@ -73,7 +73,7 @@ class mph_map {
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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_.size() + slack_.bucket_count(); }
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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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@ -100,9 +100,17 @@ class mph_map {
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return hollow_const_iterator<std::vector<value_type>>(&values_, &present_, it);
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}
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static void set_2bit_value(uint8_t *d, uint32_t i, uint8_t v) {
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d[(i >> 2)] &= ((v << ((i & 3) << 1)) | valuemask[i & 3]);
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}
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static uint32_t get_2bit_value(const uint8_t* d, uint32_t i) {
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return (d[(i >> 2)] >> (((i & 3) << 1)) & 3);
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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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const uint8_t* nests_;
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SimpleMPHIndex<Key, typename seeded_hash<HashFcn>::hash_function> index_;
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// TODO(davi) optimize slack to no hold a copy of the key
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typedef unordered_map<Key, uint32_t, HashFcn, EqualKey, Alloc> slack_type;
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@ -187,28 +195,48 @@ MPH_MAP_METHOD_DECL(void_type, erase)(const key_type& k) {
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}
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MPH_MAP_METHOD_DECL(const_iterator, find)(const key_type& k) const {
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if (__builtin_expect(!slack_.empty(), 0)) {
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auto it = slack_.find(k);
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if (it != slack_.end()) return make_iterator(values_.begin() + it->second);
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uint32_t h[4];
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auto nest = nests_[index_.hash_vector(k, reinterpret_cast<uint32_t*>(&h))];
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if (nest != kNestCollision) {
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auto vit = values_.begin() + h[nest];
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if (equal_(k, vit->first)) return make_iterator(vit);
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}
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if (__builtin_expect(index_.size() == 0, 0)) return end();
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return slow_find(k);
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}
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MPH_MAP_METHOD_DECL(const_iterator, slow_find)(const key_type& k) const {
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auto id = index_.perfect_hash(k);
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if (!present_[id]) return end();
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auto it = make_iterator(values_.begin() + id);
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if (__builtin_expect(equal_(k, it->first), 1)) return it;
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auto vit = values_.begin() + id;
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if (equal_(k, vit->first)) return make_iterator(vit);
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if (__builtin_expect(!slack_.empty(), 0)) {
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auto sit = slack_.find(k);
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if (it != 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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if (__builtin_expect(!slack_.empty(), 0)) {
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auto it = slack_.find(k);
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if (it != slack_.end()) return make_iterator(values_.begin() + it->second);
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uint32_t h[4];
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auto nest = nests_[index_.hash_vector(k, reinterpret_cast<uint32_t*>(&h))];
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if (nest != kNestCollision) {
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auto vit = values_.begin() + h[nest];
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if (equal_(k, vit->first)) return make_iterator(vit);
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}
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if (__builtin_expect(index_.size() == 0, 0)) return end();
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return slow_find(k);
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}
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MPH_MAP_METHOD_DECL(iterator, slow_find)(const key_type& k) {
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auto id = index_.perfect_hash(k);
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if (!present_[id]) return end();
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auto it = make_iterator(values_.begin() + id);
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if (__builtin_expect(equal_(k, it->first), 1)) return it;
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auto vit = values_.begin() + id;
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if (equal_(k, vit->first)) return make_iterator(vit);
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if (__builtin_expect(!slack_.empty(), 0)) {
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auto sit = slack_.find(k);
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if (it != 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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@ -65,9 +65,8 @@ struct Murmur3Fmix64bitsType {
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}
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template <class Key>
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void hash64(const Key& k, uint32_t* out) const {
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uint64_t h = fmix(*reinterpret_cast<uint64_t*>(&k));
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*reinterpret_cast<uint64_t*>(out) = h;
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*reinterpret_cast<uint64_t*>(out + 2) = h;
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*reinterpret_cast<uint64_t*>(out) = fmix(k);
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*(out + 2) = fmix(*out);
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}
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};
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@ -145,9 +144,9 @@ template <> struct seeded_hash<std::hash<long> >
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template <> struct seeded_hash<std::hash<unsigned long> >
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{ typedef seeded_hash_function<Murmur3> hash_function; };
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template <> struct seeded_hash<std::hash<long long> >
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{ typedef seeded_hash_function<Murmur3Fmix64bitsType> hash_function; };
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{ typedef seeded_hash_function<Murmur3> hash_function; };
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template <> struct seeded_hash<std::hash<unsigned long long> >
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{ typedef seeded_hash_function<Murmur3Fmix64bitsType> hash_function; };
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{ typedef seeded_hash_function<Murmur3> hash_function; };
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} // namespace cxxmph
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