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Trying perfect hash.

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This commit is contained in:
Davi de Castro Reis 2011-06-14 03:38:23 -03:00
parent cc80fcfa2b
commit 1e1cbfe606
1 changed files with 16 additions and 3 deletions
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19
cxxmph/mph_index.h
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@ -35,6 +35,11 @@ class MPHIndex {
uint32_t size() const { return m_; } uint32_t size() const { return m_; }
void clear(); void clear();
uint32_t perfect_hash_size() const { return n_; }
template <class SeededHashFcn, class Key> // must agree with Reset
uint32_t perfect_hash(const Key& x) const;
template <class SeededHashFcn, class Key> // must agree with Reset
uint32_t minimal_perfect_hash(const Key& x) const;
// Serialization machinery for mmap usage. // Serialization machinery for mmap usage.
// Serialized tables are not guaranteed to work across versions or different // Serialized tables are not guaranteed to work across versions or different
// endianness (although they could easily be made to be). // endianness (although they could easily be made to be).
@ -146,7 +151,7 @@ bool MPHIndex::Mapping(
} }
template <class SeededHashFcn, class Key> template <class SeededHashFcn, class Key>
uint32_t MPHIndex::index(const Key& key) const { uint32_t MPHIndex::perfect_hash(const Key& key) const {
uint32_t h[3]; uint32_t h[3];
for (int i = 0; i < 3; ++i) h[i] = SeededHashFcn()(key, hash_seed_[i]); for (int i = 0; i < 3; ++i) h[i] = SeededHashFcn()(key, hash_seed_[i]);
assert(r_); assert(r_);
@ -159,8 +164,16 @@ uint32_t MPHIndex::index(const Key& key) const {
assert((h[1] >> 2) <g_size_); assert((h[1] >> 2) <g_size_);
assert((h[2] >> 2) <g_size_); assert((h[2] >> 2) <g_size_);
uint32_t vertex = h[(get_2bit_value(g_, h[0]) + get_2bit_value(g_, h[1]) + get_2bit_value(g_, h[2])) % 3]; uint32_t vertex = h[(get_2bit_value(g_, h[0]) + get_2bit_value(g_, h[1]) + get_2bit_value(g_, h[2])) % 3];
// cerr << "Search found vertex " << vertex << endl; return vertex;
return Rank(vertex); }
template <class SeededHashFcn, class Key>
uint32_t MPHIndex::minimal_perfect_hash(const Key& key) const {
return Rank(perfect_hash<SeededHashFcn, Key>(key));
}
template <class SeededHashFcn, class Key>
uint32_t MPHIndex::index(const Key& key) const {
return minimal_perfect_hash<SeededHashFcn, Key>(key);
} }
template <class Key, class HashFcn = typename seeded_hash<std::tr1::hash<Key> >::hash_function> template <class Key, class HashFcn = typename seeded_hash<std::tr1::hash<Key> >::hash_function>