| // Copyright (c) 2005, Google Inc. |
| // All rights reserved. |
| // |
| // Redistribution and use in source and binary forms, with or without |
| // modification, are permitted provided that the following conditions are |
| // met: |
| // |
| // * Redistributions of source code must retain the above copyright |
| // notice, this list of conditions and the following disclaimer. |
| // * Redistributions in binary form must reproduce the above |
| // copyright notice, this list of conditions and the following disclaimer |
| // in the documentation and/or other materials provided with the |
| // distribution. |
| // * Neither the name of Google Inc. nor the names of its |
| // contributors may be used to endorse or promote products derived from |
| // this software without specific prior written permission. |
| // |
| // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| |
| // --- |
| // Author: Craig Silverstein |
| // |
| // A sparse hashtable is a particular implementation of |
| // a hashtable: one that is meant to minimize memory use. |
| // It does this by using a *sparse table* (cf sparsetable.h), |
| // which uses between 1 and 2 bits to store empty buckets |
| // (we may need another bit for hashtables that support deletion). |
| // |
| // When empty buckets are so cheap, an appealing hashtable |
| // implementation is internal probing, in which the hashtable |
| // is a single table, and collisions are resolved by trying |
| // to insert again in another bucket. The most cache-efficient |
| // internal probing schemes are linear probing (which suffers, |
| // alas, from clumping) and quadratic probing, which is what |
| // we implement by default. |
| // |
| // Deleted buckets are a bit of a pain. We have to somehow mark |
| // deleted buckets (the probing must distinguish them from empty |
| // buckets). The most principled way is to have another bitmap, |
| // but that's annoying and takes up space. Instead we let the |
| // user specify an "impossible" key. We set deleted buckets |
| // to have the impossible key. |
| // |
| // Note it is possible to change the value of the delete key |
| // on the fly; you can even remove it, though after that point |
| // the hashtable is insert_only until you set it again. |
| // |
| // You probably shouldn't use this code directly. Use |
| // <google/sparse_hash_table> or <google/sparse_hash_set> instead. |
| // |
| // You can modify the following, below: |
| // HT_OCCUPANCY_FLT -- how full before we double size |
| // HT_EMPTY_FLT -- how empty before we halve size |
| // HT_MIN_BUCKETS -- smallest bucket size |
| // HT_DEFAULT_STARTING_BUCKETS -- default bucket size at construct-time |
| // |
| // You can also change enlarge_resize_percent (which defaults to |
| // HT_OCCUPANCY_FLT), and shrink_resize_percent (which defaults to |
| // HT_EMPTY_FLT) with set_resizing_parameters(). |
| // |
| // How to decide what values to use? |
| // shrink_resize_percent's default of .4 * OCCUPANCY_FLT, is probably good. |
| // HT_MIN_BUCKETS is probably unnecessary since you can specify |
| // (indirectly) the starting number of buckets at construct-time. |
| // For enlarge_resize_percent, you can use this chart to try to trade-off |
| // expected lookup time to the space taken up. By default, this |
| // code uses quadratic probing, though you can change it to linear |
| // via _JUMP below if you really want to. |
| // |
| // From http://www.augustana.ca/~mohrj/courses/1999.fall/csc210/lecture_notes/hashing.html |
| // NUMBER OF PROBES / LOOKUP Successful Unsuccessful |
| // Quadratic collision resolution 1 - ln(1-L) - L/2 1/(1-L) - L - ln(1-L) |
| // Linear collision resolution [1+1/(1-L)]/2 [1+1/(1-L)2]/2 |
| // |
| // -- enlarge_resize_percent -- 0.10 0.50 0.60 0.75 0.80 0.90 0.99 |
| // QUADRATIC COLLISION RES. |
| // probes/successful lookup 1.05 1.44 1.62 2.01 2.21 2.85 5.11 |
| // probes/unsuccessful lookup 1.11 2.19 2.82 4.64 5.81 11.4 103.6 |
| // LINEAR COLLISION RES. |
| // probes/successful lookup 1.06 1.5 1.75 2.5 3.0 5.5 50.5 |
| // probes/unsuccessful lookup 1.12 2.5 3.6 8.5 13.0 50.0 5000.0 |
| // |
| // The value type is required to be copy constructible and default |
| // constructible, but it need not be (and commonly isn't) assignable. |
| |
| #ifndef _SPARSEHASHTABLE_H_ |
| #define _SPARSEHASHTABLE_H_ |
| |
| #ifndef SPARSEHASH_STAT_UPDATE |
| #define SPARSEHASH_STAT_UPDATE(x) ((void) 0) |
| #endif |
| |
| // The probing method |
| // Linear probing |
| // #define JUMP_(key, num_probes) ( 1 ) |
| // Quadratic probing |
| #define JUMP_(key, num_probes) ( num_probes ) |
| |
| |
| #include <google/sparsehash/sparseconfig.h> |
| #include <assert.h> |
| #include <algorithm> // For swap(), eg |
| #include <stdexcept> // For length_error |
| #include <iterator> // for facts about iterator tags |
| #include <utility> // for pair<> |
| #include <google/sparsetable> // Since that's basically what we are |
| |
| _START_GOOGLE_NAMESPACE_ |
| |
| using STL_NAMESPACE::pair; |
| |
| // The smaller this is, the faster lookup is (because the group bitmap is |
| // smaller) and the faster insert is, because there's less to move. |
| // On the other hand, there are more groups. Since group::size_type is |
| // a short, this number should be of the form 32*x + 16 to avoid waste. |
| static const u_int16_t DEFAULT_GROUP_SIZE = 48; // fits in 1.5 words |
| |
| // Hashtable class, used to implement the hashed associative containers |
| // hash_set and hash_map. |
| // |
| // Value: what is stored in the table (each bucket is a Value). |
| // Key: something in a 1-to-1 correspondence to a Value, that can be used |
| // to search for a Value in the table (find() takes a Key). |
| // HashFcn: Takes a Key and returns an integer, the more unique the better. |
| // ExtractKey: given a Value, returns the unique Key associated with it. |
| // SetKey: given a Value* and a Key, modifies the value such that |
| // ExtractKey(value) == key. We guarantee this is only called |
| // with key == deleted_key. |
| // EqualKey: Given two Keys, says whether they are the same (that is, |
| // if they are both associated with the same Value). |
| // Alloc: STL allocator to use to allocate memory. |
| |
| template <class Value, class Key, class HashFcn, |
| class ExtractKey, class SetKey, class EqualKey, class Alloc> |
| class sparse_hashtable; |
| |
| template <class V, class K, class HF, class ExK, class SetK, class EqK, class A> |
| struct sparse_hashtable_iterator; |
| |
| template <class V, class K, class HF, class ExK, class SetK, class EqK, class A> |
| struct sparse_hashtable_const_iterator; |
| |
| // As far as iterating, we're basically just a sparsetable |
| // that skips over deleted elements. |
| template <class V, class K, class HF, class ExK, class SetK, class EqK, class A> |
| struct sparse_hashtable_iterator { |
| private: |
| typedef typename A::template rebind<V>::other value_alloc_type; |
| |
| public: |
| typedef sparse_hashtable_iterator<V,K,HF,ExK,SetK,EqK,A> iterator; |
| typedef sparse_hashtable_const_iterator<V,K,HF,ExK,SetK,EqK,A> const_iterator; |
| typedef typename sparsetable<V,DEFAULT_GROUP_SIZE,A>::nonempty_iterator |
| st_iterator; |
| |
| typedef STL_NAMESPACE::forward_iterator_tag iterator_category; |
| typedef V value_type; |
| typedef typename value_alloc_type::difference_type difference_type; |
| typedef typename value_alloc_type::size_type size_type; |
| typedef typename value_alloc_type::reference reference; |
| typedef typename value_alloc_type::pointer pointer; |
| |
| // "Real" constructor and default constructor |
| sparse_hashtable_iterator(const sparse_hashtable<V,K,HF,ExK,SetK,EqK,A> *h, |
| st_iterator it, st_iterator it_end) |
| : ht(h), pos(it), end(it_end) { advance_past_deleted(); } |
| sparse_hashtable_iterator() { } // not ever used internally |
| // The default destructor is fine; we don't define one |
| // The default operator= is fine; we don't define one |
| |
| // Happy dereferencer |
| reference operator*() const { return *pos; } |
| pointer operator->() const { return &(operator*()); } |
| |
| // Arithmetic. The only hard part is making sure that |
| // we're not on a marked-deleted array element |
| void advance_past_deleted() { |
| while ( pos != end && ht->test_deleted(*this) ) |
| ++pos; |
| } |
| iterator& operator++() { |
| assert(pos != end); ++pos; advance_past_deleted(); return *this; |
| } |
| iterator operator++(int) { iterator tmp(*this); ++*this; return tmp; } |
| |
| // Comparison. |
| bool operator==(const iterator& it) const { return pos == it.pos; } |
| bool operator!=(const iterator& it) const { return pos != it.pos; } |
| |
| |
| // The actual data |
| const sparse_hashtable<V,K,HF,ExK,SetK,EqK,A> *ht; |
| st_iterator pos, end; |
| }; |
| |
| // Now do it all again, but with const-ness! |
| template <class V, class K, class HF, class ExK, class SetK, class EqK, class A> |
| struct sparse_hashtable_const_iterator { |
| private: |
| typedef typename A::template rebind<V>::other value_alloc_type; |
| |
| public: |
| typedef sparse_hashtable_iterator<V,K,HF,ExK,SetK,EqK,A> iterator; |
| typedef sparse_hashtable_const_iterator<V,K,HF,ExK,SetK,EqK,A> const_iterator; |
| typedef typename sparsetable<V,DEFAULT_GROUP_SIZE,A>::const_nonempty_iterator |
| st_iterator; |
| |
| typedef STL_NAMESPACE::forward_iterator_tag iterator_category; |
| typedef V value_type; |
| typedef typename value_alloc_type::difference_type difference_type; |
| typedef typename value_alloc_type::size_type size_type; |
| typedef typename value_alloc_type::const_reference reference; |
| typedef typename value_alloc_type::const_pointer pointer; |
| |
| // "Real" constructor and default constructor |
| sparse_hashtable_const_iterator(const sparse_hashtable<V,K,HF,ExK,SetK,EqK,A> *h, |
| st_iterator it, st_iterator it_end) |
| : ht(h), pos(it), end(it_end) { advance_past_deleted(); } |
| // This lets us convert regular iterators to const iterators |
| sparse_hashtable_const_iterator() { } // never used internally |
| sparse_hashtable_const_iterator(const iterator &it) |
| : ht(it.ht), pos(it.pos), end(it.end) { } |
| // The default destructor is fine; we don't define one |
| // The default operator= is fine; we don't define one |
| |
| // Happy dereferencer |
| reference operator*() const { return *pos; } |
| pointer operator->() const { return &(operator*()); } |
| |
| // Arithmetic. The only hard part is making sure that |
| // we're not on a marked-deleted array element |
| void advance_past_deleted() { |
| while ( pos != end && ht->test_deleted(*this) ) |
| ++pos; |
| } |
| const_iterator& operator++() { |
| assert(pos != end); ++pos; advance_past_deleted(); return *this; |
| } |
| const_iterator operator++(int) { const_iterator tmp(*this); ++*this; return tmp; } |
| |
| // Comparison. |
| bool operator==(const const_iterator& it) const { return pos == it.pos; } |
| bool operator!=(const const_iterator& it) const { return pos != it.pos; } |
| |
| |
| // The actual data |
| const sparse_hashtable<V,K,HF,ExK,SetK,EqK,A> *ht; |
| st_iterator pos, end; |
| }; |
| |
| // And once again, but this time freeing up memory as we iterate |
| template <class V, class K, class HF, class ExK, class SetK, class EqK, class A> |
| struct sparse_hashtable_destructive_iterator { |
| private: |
| typedef typename A::template rebind<V>::other value_alloc_type; |
| |
| public: |
| typedef sparse_hashtable_destructive_iterator<V,K,HF,ExK,SetK,EqK,A> iterator; |
| typedef typename sparsetable<V,DEFAULT_GROUP_SIZE,A>::destructive_iterator |
| st_iterator; |
| |
| typedef STL_NAMESPACE::forward_iterator_tag iterator_category; |
| typedef V value_type; |
| typedef typename value_alloc_type::difference_type difference_type; |
| typedef typename value_alloc_type::size_type size_type; |
| typedef typename value_alloc_type::reference reference; |
| typedef typename value_alloc_type::pointer pointer; |
| |
| // "Real" constructor and default constructor |
| sparse_hashtable_destructive_iterator(const |
| sparse_hashtable<V,K,HF,ExK,SetK,EqK,A> *h, |
| st_iterator it, st_iterator it_end) |
| : ht(h), pos(it), end(it_end) { advance_past_deleted(); } |
| sparse_hashtable_destructive_iterator() { } // never used internally |
| // The default destructor is fine; we don't define one |
| // The default operator= is fine; we don't define one |
| |
| // Happy dereferencer |
| reference operator*() const { return *pos; } |
| pointer operator->() const { return &(operator*()); } |
| |
| // Arithmetic. The only hard part is making sure that |
| // we're not on a marked-deleted array element |
| void advance_past_deleted() { |
| while ( pos != end && ht->test_deleted(*this) ) |
| ++pos; |
| } |
| iterator& operator++() { |
| assert(pos != end); ++pos; advance_past_deleted(); return *this; |
| } |
| iterator operator++(int) { iterator tmp(*this); ++*this; return tmp; } |
| |
| // Comparison. |
| bool operator==(const iterator& it) const { return pos == it.pos; } |
| bool operator!=(const iterator& it) const { return pos != it.pos; } |
| |
| |
| // The actual data |
| const sparse_hashtable<V,K,HF,ExK,SetK,EqK,A> *ht; |
| st_iterator pos, end; |
| }; |
| |
| |
| template <class Value, class Key, class HashFcn, |
| class ExtractKey, class SetKey, class EqualKey, class Alloc> |
| class sparse_hashtable { |
| private: |
| typedef typename Alloc::template rebind<Value>::other value_alloc_type; |
| |
| public: |
| typedef Key key_type; |
| typedef Value value_type; |
| typedef HashFcn hasher; |
| typedef EqualKey key_equal; |
| typedef Alloc allocator_type; |
| |
| typedef typename value_alloc_type::size_type size_type; |
| typedef typename value_alloc_type::difference_type difference_type; |
| typedef typename value_alloc_type::reference reference; |
| typedef typename value_alloc_type::const_reference const_reference; |
| typedef typename value_alloc_type::pointer pointer; |
| typedef typename value_alloc_type::const_pointer const_pointer; |
| typedef sparse_hashtable_iterator<Value, Key, HashFcn, ExtractKey, |
| SetKey, EqualKey, Alloc> |
| iterator; |
| |
| typedef sparse_hashtable_const_iterator<Value, Key, HashFcn, ExtractKey, |
| SetKey, EqualKey, Alloc> |
| const_iterator; |
| |
| typedef sparse_hashtable_destructive_iterator<Value, Key, HashFcn, ExtractKey, |
| SetKey, EqualKey, Alloc> |
| destructive_iterator; |
| |
| // These come from tr1. For us they're the same as regular iterators. |
| typedef iterator local_iterator; |
| typedef const_iterator const_local_iterator; |
| |
| // How full we let the table get before we resize, by default. |
| // Knuth says .8 is good -- higher causes us to probe too much, |
| // though it saves memory. |
| static const float HT_OCCUPANCY_FLT; // = 0.8f; |
| |
| // How empty we let the table get before we resize lower, by default. |
| // (0.0 means never resize lower.) |
| // It should be less than OCCUPANCY_FLT / 2 or we thrash resizing |
| static const float HT_EMPTY_FLT; // = 0.4 * HT_OCCUPANCY_FLT; |
| |
| // Minimum size we're willing to let hashtables be. |
| // Must be a power of two, and at least 4. |
| // Note, however, that for a given hashtable, the initial size is a |
| // function of the first constructor arg, and may be >HT_MIN_BUCKETS. |
| static const size_type HT_MIN_BUCKETS = 4; |
| |
| // By default, if you don't specify a hashtable size at |
| // construction-time, we use this size. Must be a power of two, and |
| // at least HT_MIN_BUCKETS. |
| static const size_type HT_DEFAULT_STARTING_BUCKETS = 32; |
| |
| // ITERATOR FUNCTIONS |
| iterator begin() { return iterator(this, table.nonempty_begin(), |
| table.nonempty_end()); } |
| iterator end() { return iterator(this, table.nonempty_end(), |
| table.nonempty_end()); } |
| const_iterator begin() const { return const_iterator(this, |
| table.nonempty_begin(), |
| table.nonempty_end()); } |
| const_iterator end() const { return const_iterator(this, |
| table.nonempty_end(), |
| table.nonempty_end()); } |
| |
| // These come from tr1 unordered_map. They iterate over 'bucket' n. |
| // For sparsehashtable, we could consider each 'group' to be a bucket, |
| // I guess, but I don't really see the point. We'll just consider |
| // bucket n to be the n-th element of the sparsetable, if it's occupied, |
| // or some empty element, otherwise. |
| local_iterator begin(size_type i) { |
| if (table.test(i)) |
| return local_iterator(this, table.get_iter(i), table.nonempty_end()); |
| else |
| return local_iterator(this, table.nonempty_end(), table.nonempty_end()); |
| } |
| local_iterator end(size_type i) { |
| local_iterator it = begin(i); |
| if (table.test(i) && !test_deleted(i)) |
| ++it; |
| return it; |
| } |
| const_local_iterator begin(size_type i) const { |
| if (table.test(i)) |
| return const_local_iterator(this, table.get_iter(i), |
| table.nonempty_end()); |
| else |
| return const_local_iterator(this, table.nonempty_end(), |
| table.nonempty_end()); |
| } |
| const_local_iterator end(size_type i) const { |
| const_local_iterator it = begin(i); |
| if (table.test(i) && !test_deleted(i)) |
| ++it; |
| return it; |
| } |
| |
| // This is used when resizing |
| destructive_iterator destructive_begin() { |
| return destructive_iterator(this, table.destructive_begin(), |
| table.destructive_end()); |
| } |
| destructive_iterator destructive_end() { |
| return destructive_iterator(this, table.destructive_end(), |
| table.destructive_end()); |
| } |
| |
| |
| // ACCESSOR FUNCTIONS for the things we templatize on, basically |
| hasher hash_funct() const { return settings; } |
| key_equal key_eq() const { return settings; } |
| |
| // Accessor function for statistics gathering. |
| int num_table_copies() const { return num_ht_copies; } |
| |
| private: |
| // We need to copy values when we set the special marker for deleted |
| // elements, but, annoyingly, we can't just use the copy assignment |
| // operator because value_type might not be assignable (it's often |
| // pair<const X, Y>). We use explicit destructor invocation and |
| // placement new to get around this. Arg. |
| void set_value(pointer dst, const_reference src) { |
| dst->~value_type(); // delete the old value, if any |
| new(dst) value_type(src); |
| } |
| |
| // This is used as a tag for the copy constructor, saying to destroy its |
| // arg We have two ways of destructively copying: with potentially growing |
| // the hashtable as we copy, and without. To make sure the outside world |
| // can't do a destructive copy, we make the typename private. |
| enum MoveDontCopyT {MoveDontCopy, MoveDontGrow}; |
| |
| |
| // DELETE HELPER FUNCTIONS |
| // This lets the user describe a key that will indicate deleted |
| // table entries. This key should be an "impossible" entry -- |
| // if you try to insert it for real, you won't be able to retrieve it! |
| // (NB: while you pass in an entire value, only the key part is looked |
| // at. This is just because I don't know how to assign just a key.) |
| private: |
| void squash_deleted() { // gets rid of any deleted entries we have |
| if ( num_deleted ) { // get rid of deleted before writing |
| sparse_hashtable tmp(MoveDontGrow, *this); |
| swap(tmp); // now we are tmp |
| } |
| assert(num_deleted == 0); |
| } |
| |
| bool test_deleted_key(const key_type& key) const { |
| // The num_deleted test is crucial for read(): after read(), the ht values |
| // are garbage, and we don't want to think some of them are deleted. |
| // Invariant: !use_deleted implies num_deleted is 0. |
| assert(use_deleted || num_deleted == 0); |
| return num_deleted > 0 && equals(key_info.delkey, key); |
| } |
| |
| public: |
| void set_deleted_key(const key_type &key) { |
| // It's only safe to change what "deleted" means if we purge deleted guys |
| squash_deleted(); |
| use_deleted = true; |
| key_info.delkey = key; |
| } |
| void clear_deleted_key() { |
| squash_deleted(); |
| use_deleted = false; |
| } |
| key_type deleted_key() const { |
| assert(use_deleted); |
| return key_info.delkey; |
| } |
| |
| // These are public so the iterators can use them |
| // True if the item at position bucknum is "deleted" marker |
| bool test_deleted(size_type bucknum) const { |
| if (num_deleted == 0 || !table.test(bucknum)) return false; |
| return test_deleted_key(get_key(table.unsafe_get(bucknum))); |
| } |
| bool test_deleted(const iterator &it) const { |
| if (!use_deleted) return false; |
| return test_deleted_key(get_key(*it)); |
| } |
| bool test_deleted(const const_iterator &it) const { |
| if (!use_deleted) return false; |
| return test_deleted_key(get_key(*it)); |
| } |
| bool test_deleted(const destructive_iterator &it) const { |
| if (!use_deleted) return false; |
| return test_deleted_key(get_key(*it)); |
| } |
| |
| // Set it so test_deleted is true. true if object didn't used to be deleted. |
| bool set_deleted(iterator &it) { |
| assert(use_deleted); |
| bool retval = !test_deleted(it); |
| // &* converts from iterator to value-type. |
| set_key(&(*it), key_info.delkey); |
| return retval; |
| } |
| // Set it so test_deleted is false. true if object used to be deleted. |
| bool clear_deleted(iterator &it) { |
| assert(use_deleted); |
| // Happens automatically when we assign something else in its place. |
| return test_deleted(it); |
| } |
| |
| // We also allow to set/clear the deleted bit on a const iterator. |
| // We allow a const_iterator for the same reason you can delete a |
| // const pointer: it's convenient, and semantically you can't use |
| // 'it' after it's been deleted anyway, so its const-ness doesn't |
| // really matter. |
| bool set_deleted(const_iterator &it) { |
| assert(use_deleted); // bad if set_deleted_key() wasn't called |
| bool retval = !test_deleted(it); |
| set_key(const_cast<pointer>(&(*it)), key_info.delkey); |
| return retval; |
| } |
| // Set it so test_deleted is false. true if object used to be deleted. |
| bool clear_deleted(const_iterator &it) { |
| assert(use_deleted); // bad if set_deleted_key() wasn't called |
| return test_deleted(it); |
| } |
| |
| // FUNCTIONS CONCERNING SIZE |
| public: |
| size_type size() const { return table.num_nonempty() - num_deleted; } |
| size_type max_size() const { return table.max_size(); } |
| bool empty() const { return size() == 0; } |
| size_type bucket_count() const { return table.size(); } |
| size_type max_bucket_count() const { return max_size(); } |
| // These are tr1 methods. Their idea of 'bucket' doesn't map well to |
| // what we do. We just say every bucket has 0 or 1 items in it. |
| size_type bucket_size(size_type i) const { |
| return begin(i) == end(i) ? 0 : 1; |
| } |
| |
| |
| private: |
| // Because of the above, size_type(-1) is never legal; use it for errors |
| static const size_type ILLEGAL_BUCKET = size_type(-1); |
| |
| private: |
| // This is the smallest size a hashtable can be without being too crowded |
| // If you like, you can give a min #buckets as well as a min #elts |
| size_type min_size(size_type num_elts, size_type min_buckets_wanted) { |
| size_type sz = HT_MIN_BUCKETS; // min buckets allowed |
| while ( sz < min_buckets_wanted || |
| num_elts >= |
| static_cast<size_type>(sz * settings.enlarge_resize_percent) ) { |
| if (sz * 2 < sz) |
| throw std::length_error("resize overflow"); // protect against overflow |
| sz *= 2; |
| } |
| return sz; |
| } |
| |
| // Used after a string of deletes |
| void maybe_shrink() { |
| assert(table.num_nonempty() >= num_deleted); |
| assert((bucket_count() & (bucket_count()-1)) == 0); // is a power of two |
| assert(bucket_count() >= HT_MIN_BUCKETS); |
| |
| // If you construct a hashtable with < HT_DEFAULT_STARTING_BUCKETS, |
| // we'll never shrink until you get relatively big, and we'll never |
| // shrink below HT_DEFAULT_STARTING_BUCKETS. Otherwise, something |
| // like "dense_hash_set<int> x; x.insert(4); x.erase(4);" will |
| // shrink us down to HT_MIN_BUCKETS buckets, which is too small. |
| const size_type num_remain = table.num_nonempty() - num_deleted; |
| if (settings.shrink_threshold > 0 && |
| num_remain < settings.shrink_threshold && |
| bucket_count() > HT_DEFAULT_STARTING_BUCKETS) { |
| size_type sz = bucket_count() / 2; // find how much we should shrink |
| while (sz > HT_DEFAULT_STARTING_BUCKETS && |
| num_remain < sz * settings.shrink_resize_percent) { |
| sz /= 2; // stay a power of 2 |
| } |
| sparse_hashtable tmp(MoveDontCopy, *this, sz); |
| swap(tmp); // now we are tmp |
| } |
| consider_shrink = false; // because we just considered it |
| } |
| |
| // We'll let you resize a hashtable -- though this makes us copy all! |
| // When you resize, you say, "make it big enough for this many more elements" |
| void resize_delta(size_type delta) { |
| if ( consider_shrink ) // see if lots of deletes happened |
| maybe_shrink(); |
| if ( bucket_count() >= HT_MIN_BUCKETS && |
| (table.num_nonempty() + delta) <= settings.enlarge_threshold ) |
| return; // we're ok as we are |
| |
| // Sometimes, we need to resize just to get rid of all the |
| // "deleted" buckets that are clogging up the hashtable. So when |
| // deciding whether to resize, count the deleted buckets (which |
| // are currently taking up room). But later, when we decide what |
| // size to resize to, *don't* count deleted buckets, since they |
| // get discarded during the resize. |
| const size_type needed_size = min_size(table.num_nonempty() + delta, 0); |
| if ( needed_size > bucket_count() ) { // we don't have enough buckets |
| size_type resize_to = min_size(table.num_nonempty() - num_deleted + delta, |
| bucket_count()); |
| if (resize_to < needed_size) { |
| // This situation means that we have enough deleted elements, |
| // that once we purge them, we won't actually have needed to |
| // grow. But we may want to grow anyway: if we just purge one |
| // element, say, we'll have to grow anyway next time we |
| // insert. Might as well grow now, since we're already going |
| // through the trouble of copying (in order to purge the |
| // deleted elements). |
| const size_type target = |
| static_cast<size_type>(resize_to*2 * settings.shrink_resize_percent); |
| if (table.num_nonempty() - num_deleted + delta >= target) { |
| // Good, we won't be below the shrink threshhold even if we double. |
| resize_to *= 2; |
| } |
| } |
| |
| sparse_hashtable tmp(MoveDontCopy, *this, resize_to); |
| swap(tmp); // now we are tmp |
| } |
| } |
| |
| // Used to actually do the rehashing when we grow/shrink a hashtable |
| void copy_from(const sparse_hashtable &ht, size_type min_buckets_wanted) { |
| clear(); // clear table, set num_deleted to 0 |
| |
| // If we need to change the size of our table, do it now |
| const size_type resize_to = min_size(ht.size(), min_buckets_wanted); |
| if ( resize_to > bucket_count() ) { // we don't have enough buckets |
| table.resize(resize_to); // sets the number of buckets |
| reset_thresholds(); |
| } |
| |
| // We use a normal iterator to get non-deleted bcks from ht |
| // We could use insert() here, but since we know there are |
| // no duplicates and no deleted items, we can be more efficient |
| assert((bucket_count() & (bucket_count()-1)) == 0); // a power of two |
| for ( const_iterator it = ht.begin(); it != ht.end(); ++it ) { |
| size_type num_probes = 0; // how many times we've probed |
| size_type bucknum; |
| const size_type bucket_count_minus_one = bucket_count() - 1; |
| for (bucknum = hash(get_key(*it)) & bucket_count_minus_one; |
| table.test(bucknum); // not empty |
| bucknum = (bucknum + JUMP_(key, num_probes)) & bucket_count_minus_one) { |
| ++num_probes; |
| assert(num_probes < bucket_count()); // or else the hashtable is full |
| } |
| table.set(bucknum, *it); // copies the value to here |
| } |
| num_ht_copies++; |
| } |
| |
| // Implementation is like copy_from, but it destroys the table of the |
| // "from" guy by freeing sparsetable memory as we iterate. This is |
| // useful in resizing, since we're throwing away the "from" guy anyway. |
| void move_from(MoveDontCopyT mover, sparse_hashtable &ht, |
| size_type min_buckets_wanted) { |
| clear(); // clear table, set num_deleted to 0 |
| |
| // If we need to change the size of our table, do it now |
| size_type resize_to; |
| if ( mover == MoveDontGrow ) |
| resize_to = ht.bucket_count(); // keep same size as old ht |
| else // MoveDontCopy |
| resize_to = min_size(ht.size(), min_buckets_wanted); |
| if ( resize_to > bucket_count() ) { // we don't have enough buckets |
| table.resize(resize_to); // sets the number of buckets |
| reset_thresholds(); |
| } |
| |
| // We use a normal iterator to get non-deleted bcks from ht |
| // We could use insert() here, but since we know there are |
| // no duplicates and no deleted items, we can be more efficient |
| assert( (bucket_count() & (bucket_count()-1)) == 0); // a power of two |
| // THIS IS THE MAJOR LINE THAT DIFFERS FROM COPY_FROM(): |
| for ( destructive_iterator it = ht.destructive_begin(); |
| it != ht.destructive_end(); ++it ) { |
| size_type num_probes = 0; // how many times we've probed |
| size_type bucknum; |
| for ( bucknum = hash(get_key(*it)) & (bucket_count()-1); // h % buck_cnt |
| table.test(bucknum); // not empty |
| bucknum = (bucknum + JUMP_(key, num_probes)) & (bucket_count()-1) ) { |
| ++num_probes; |
| assert(num_probes < bucket_count()); // or else the hashtable is full |
| } |
| table.set(bucknum, *it); // copies the value to here |
| } |
| num_ht_copies++; |
| } |
| |
| |
| // Required by the spec for hashed associative container |
| public: |
| // Though the docs say this should be num_buckets, I think it's much |
| // more useful as num_elements. As a special feature, calling with |
| // req_elements==0 will cause us to shrink if we can, saving space. |
| void resize(size_type req_elements) { // resize to this or larger |
| if ( consider_shrink || req_elements == 0 ) |
| maybe_shrink(); |
| if ( req_elements > table.num_nonempty() ) // we only grow |
| resize_delta(req_elements - table.num_nonempty()); |
| } |
| |
| // Get and change the value of shrink_resize_percent and |
| // enlarge_resize_percent. The description at the beginning of this |
| // file explains how to choose the values. Setting the shrink |
| // parameter to 0.0 ensures that the table never shrinks. |
| void get_resizing_parameters(float* shrink, float* grow) const { |
| *shrink = settings.shrink_resize_percent; |
| *grow = settings.enlarge_resize_percent; |
| } |
| void set_resizing_parameters(float shrink, float grow) { |
| assert(shrink >= 0.0); |
| assert(grow <= 1.0); |
| if (shrink > grow/2.0f) |
| shrink = grow / 2.0f; // otherwise we thrash hashtable size |
| settings.shrink_resize_percent = shrink; |
| settings.enlarge_resize_percent = grow; |
| reset_thresholds(); |
| } |
| |
| // CONSTRUCTORS -- as required by the specs, we take a size, |
| // but also let you specify a hashfunction, key comparator, |
| // and key extractor. We also define a copy constructor and =. |
| // DESTRUCTOR -- the default is fine, surprisingly. |
| explicit sparse_hashtable(size_type expected_max_items_in_table = 0, |
| const HashFcn& hf = HashFcn(), |
| const EqualKey& eql = EqualKey(), |
| const ExtractKey& ext = ExtractKey(), |
| const SetKey& set = SetKey()) |
| : settings(hf, eql), |
| key_info(ext, set), |
| use_deleted(false), |
| num_ht_copies(0), |
| num_deleted(0), |
| table(expected_max_items_in_table == 0 |
| ? HT_DEFAULT_STARTING_BUCKETS |
| : min_size(expected_max_items_in_table, 0)) { |
| reset_thresholds(); |
| } |
| |
| // As a convenience for resize(), we allow an optional second argument |
| // which lets you make this new hashtable a different size than ht. |
| // We also provide a mechanism of saying you want to "move" the ht argument |
| // into us instead of copying. |
| sparse_hashtable(const sparse_hashtable& ht, |
| size_type min_buckets_wanted = HT_DEFAULT_STARTING_BUCKETS) |
| : settings(ht.settings), |
| key_info(ht.key_info), |
| use_deleted(ht.use_deleted), |
| num_ht_copies(ht.num_ht_copies), |
| num_deleted(0), |
| table() { |
| reset_thresholds(); |
| copy_from(ht, min_buckets_wanted); // copy_from() ignores deleted entries |
| } |
| sparse_hashtable(MoveDontCopyT mover, sparse_hashtable& ht, |
| size_type min_buckets_wanted = HT_DEFAULT_STARTING_BUCKETS) |
| : settings(ht.settings), |
| key_info(ht.key_info), |
| use_deleted(ht.use_deleted), |
| num_ht_copies(ht.num_ht_copies), |
| num_deleted(0), |
| table() { |
| reset_thresholds(); |
| move_from(mover, ht, min_buckets_wanted); // ignores deleted entries |
| } |
| |
| sparse_hashtable& operator= (const sparse_hashtable& ht) { |
| if (&ht == this) return *this; // don't copy onto ourselves |
| settings = ht.settings; |
| key_info = ht.key_info; |
| use_deleted = ht.use_deleted; |
| num_ht_copies = ht.num_ht_copies; |
| // copy_from() calls clear and sets num_deleted to 0 too |
| copy_from(ht, HT_MIN_BUCKETS); |
| return *this; |
| } |
| |
| // Many STL algorithms use swap instead of copy constructors |
| void swap(sparse_hashtable& ht) { |
| STL_NAMESPACE::swap(settings, ht.settings); |
| STL_NAMESPACE::swap(key_info, ht.key_info); |
| STL_NAMESPACE::swap(use_deleted, ht.use_deleted); |
| STL_NAMESPACE::swap(num_ht_copies, ht.num_ht_copies); |
| STL_NAMESPACE::swap(num_deleted, ht.num_deleted); |
| table.swap(ht.table); |
| reset_thresholds(); |
| ht.reset_thresholds(); |
| } |
| |
| // It's always nice to be able to clear a table without deallocating it |
| void clear() { |
| if (!empty() || (num_deleted != 0)) { |
| table.clear(); |
| } |
| reset_thresholds(); |
| num_deleted = 0; |
| } |
| |
| |
| // LOOKUP ROUTINES |
| private: |
| // Returns a pair of positions: 1st where the object is, 2nd where |
| // it would go if you wanted to insert it. 1st is ILLEGAL_BUCKET |
| // if object is not found; 2nd is ILLEGAL_BUCKET if it is. |
| // Note: because of deletions where-to-insert is not trivial: it's the |
| // first deleted bucket we see, as long as we don't find the key later |
| pair<size_type, size_type> find_position(const key_type &key) const { |
| size_type num_probes = 0; // how many times we've probed |
| const size_type bucket_count_minus_one = bucket_count() - 1; |
| size_type bucknum = hash(key) & bucket_count_minus_one; |
| size_type insert_pos = ILLEGAL_BUCKET; // where we would insert |
| SPARSEHASH_STAT_UPDATE(total_lookups += 1); |
| while ( 1 ) { // probe until something happens |
| if ( !table.test(bucknum) ) { // bucket is empty |
| SPARSEHASH_STAT_UPDATE(total_probes += num_probes); |
| if ( insert_pos == ILLEGAL_BUCKET ) // found no prior place to insert |
| return pair<size_type,size_type>(ILLEGAL_BUCKET, bucknum); |
| else |
| return pair<size_type,size_type>(ILLEGAL_BUCKET, insert_pos); |
| |
| } else if ( test_deleted(bucknum) ) {// keep searching, but mark to insert |
| if ( insert_pos == ILLEGAL_BUCKET ) |
| insert_pos = bucknum; |
| |
| } else if ( equals(key, get_key(table.unsafe_get(bucknum))) ) { |
| SPARSEHASH_STAT_UPDATE(total_probes += num_probes); |
| return pair<size_type,size_type>(bucknum, ILLEGAL_BUCKET); |
| } |
| ++num_probes; // we're doing another probe |
| bucknum = (bucknum + JUMP_(key, num_probes)) & bucket_count_minus_one; |
| assert(num_probes < bucket_count()); // don't probe too many times! |
| } |
| } |
| |
| public: |
| iterator find(const key_type& key) { |
| if ( size() == 0 ) return end(); |
| pair<size_type, size_type> pos = find_position(key); |
| if ( pos.first == ILLEGAL_BUCKET ) // alas, not there |
| return end(); |
| else |
| return iterator(this, table.get_iter(pos.first), table.nonempty_end()); |
| } |
| |
| const_iterator find(const key_type& key) const { |
| if ( size() == 0 ) return end(); |
| pair<size_type, size_type> pos = find_position(key); |
| if ( pos.first == ILLEGAL_BUCKET ) // alas, not there |
| return end(); |
| else |
| return const_iterator(this, |
| table.get_iter(pos.first), table.nonempty_end()); |
| } |
| |
| // This is a tr1 method: the bucket a given key is in, or what bucket |
| // it would be put in, if it were to be inserted. Shrug. |
| size_type bucket(const key_type& key) const { |
| pair<size_type, size_type> pos = find_position(key); |
| return pos.first == ILLEGAL_BUCKET ? pos.second : pos.first; |
| } |
| |
| // Counts how many elements have key key. For maps, it's either 0 or 1. |
| size_type count(const key_type &key) const { |
| pair<size_type, size_type> pos = find_position(key); |
| return pos.first == ILLEGAL_BUCKET ? 0 : 1; |
| } |
| |
| // Likewise, equal_range doesn't really make sense for us. Oh well. |
| pair<iterator,iterator> equal_range(const key_type& key) { |
| iterator pos = find(key); // either an iterator or end |
| if (pos == end()) { |
| return pair<iterator,iterator>(pos, pos); |
| } else { |
| const iterator startpos = pos++; |
| return pair<iterator,iterator>(startpos, pos); |
| } |
| } |
| pair<const_iterator,const_iterator> equal_range(const key_type& key) const { |
| const_iterator pos = find(key); // either an iterator or end |
| if (pos == end()) { |
| return pair<const_iterator,const_iterator>(pos, pos); |
| } else { |
| const const_iterator startpos = pos++; |
| return pair<const_iterator,const_iterator>(startpos, pos); |
| } |
| } |
| |
| |
| // INSERTION ROUTINES |
| private: |
| // If you know *this is big enough to hold obj, use this routine |
| pair<iterator, bool> insert_noresize(const_reference obj) { |
| // First, double-check we're not inserting delkey |
| assert(!use_deleted || !equals(get_key(obj), key_info.delkey)); |
| const pair<size_type,size_type> pos = find_position(get_key(obj)); |
| if ( pos.first != ILLEGAL_BUCKET) { // object was already there |
| return pair<iterator,bool>(iterator(this, table.get_iter(pos.first), |
| table.nonempty_end()), |
| false); // false: we didn't insert |
| } else { // pos.second says where to put it |
| if ( test_deleted(pos.second) ) { // just replace if it's been del. |
| // The set() below will undelete this object. We just worry about stats |
| assert(num_deleted > 0); |
| --num_deleted; // used to be, now it isn't |
| } |
| table.set(pos.second, obj); |
| return pair<iterator,bool>(iterator(this, table.get_iter(pos.second), |
| table.nonempty_end()), |
| true); // true: we did insert |
| } |
| } |
| |
| public: |
| // This is the normal insert routine, used by the outside world |
| pair<iterator, bool> insert(const_reference obj) { |
| resize_delta(1); // adding an object, grow if need be |
| return insert_noresize(obj); |
| } |
| |
| // When inserting a lot at a time, we specialize on the type of iterator |
| template <class InputIterator> |
| void insert(InputIterator f, InputIterator l) { |
| // specializes on iterator type |
| insert(f, l, typename STL_NAMESPACE::iterator_traits<InputIterator>::iterator_category()); |
| } |
| |
| // Iterator supports operator-, resize before inserting |
| template <class ForwardIterator> |
| void insert(ForwardIterator f, ForwardIterator l, |
| STL_NAMESPACE::forward_iterator_tag) { |
| size_type n = STL_NAMESPACE::distance(f, l); // TODO(csilvers): standard? |
| resize_delta(n); |
| for ( ; n > 0; --n, ++f) |
| insert_noresize(*f); |
| } |
| |
| // Arbitrary iterator, can't tell how much to resize |
| template <class InputIterator> |
| void insert(InputIterator f, InputIterator l, |
| STL_NAMESPACE::input_iterator_tag) { |
| for ( ; f != l; ++f) |
| insert(*f); |
| } |
| |
| |
| // DELETION ROUTINES |
| size_type erase(const key_type& key) { |
| // First, double-check we're not erasing delkey. |
| assert(!use_deleted || !equals(key, key_info.delkey)); |
| const_iterator pos = find(key); // shrug: shouldn't need to be const |
| if ( pos != end() ) { |
| assert(!test_deleted(pos)); // or find() shouldn't have returned it |
| set_deleted(pos); |
| ++num_deleted; |
| consider_shrink = true; // will think about shrink after next insert |
| return 1; // because we deleted one thing |
| } else { |
| return 0; // because we deleted nothing |
| } |
| } |
| |
| // We return the iterator past the deleted item. |
| void erase(iterator pos) { |
| if ( pos == end() ) return; // sanity check |
| if ( set_deleted(pos) ) { // true if object has been newly deleted |
| ++num_deleted; |
| consider_shrink = true; // will think about shrink after next insert |
| } |
| } |
| |
| void erase(iterator f, iterator l) { |
| for ( ; f != l; ++f) { |
| if ( set_deleted(f) ) // should always be true |
| ++num_deleted; |
| } |
| consider_shrink = true; // will think about shrink after next insert |
| } |
| |
| // We allow you to erase a const_iterator just like we allow you to |
| // erase an iterator. This is in parallel to 'delete': you can delete |
| // a const pointer just like a non-const pointer. The logic is that |
| // you can't use the object after it's erased anyway, so it doesn't matter |
| // if it's const or not. |
| void erase(const_iterator pos) { |
| if ( pos == end() ) return; // sanity check |
| if ( set_deleted(pos) ) { // true if object has been newly deleted |
| ++num_deleted; |
| consider_shrink = true; // will think about shrink after next insert |
| } |
| } |
| void erase(const_iterator f, const_iterator l) { |
| for ( ; f != l; ++f) { |
| if ( set_deleted(f) ) // should always be true |
| ++num_deleted; |
| } |
| consider_shrink = true; // will think about shrink after next insert |
| } |
| |
| |
| // COMPARISON |
| bool operator==(const sparse_hashtable& ht) const { |
| if (size() != ht.size()) { |
| return false; |
| } else if (this == &ht) { |
| return true; |
| } else { |
| // Iterate through the elements in "this" and see if the |
| // corresponding element is in ht |
| for ( const_iterator it = begin(); it != end(); ++it ) { |
| const_iterator it2 = ht.find(get_key(*it)); |
| if ((it2 == ht.end()) || (*it != *it2)) { |
| return false; |
| } |
| } |
| return true; |
| } |
| } |
| bool operator!=(const sparse_hashtable& ht) const { |
| return !(*this == ht); |
| } |
| |
| |
| // I/O |
| // We support reading and writing hashtables to disk. NOTE that |
| // this only stores the hashtable metadata, not the stuff you've |
| // actually put in the hashtable! Alas, since I don't know how to |
| // write a hasher or key_equal, you have to make sure everything |
| // but the table is the same. We compact before writing. |
| bool write_metadata(FILE *fp) { |
| squash_deleted(); // so we don't have to worry about delkey |
| return table.write_metadata(fp); |
| } |
| |
| bool read_metadata(FILE *fp) { |
| num_deleted = 0; // since we got rid before writing |
| bool result = table.read_metadata(fp); |
| reset_thresholds(); |
| return result; |
| } |
| |
| // Only meaningful if value_type is a POD. |
| bool write_nopointer_data(FILE *fp) { |
| return table.write_nopointer_data(fp); |
| } |
| |
| // Only meaningful if value_type is a POD. |
| bool read_nopointer_data(FILE *fp) { |
| return table.read_nopointer_data(fp); |
| } |
| |
| private: |
| // Table is the main storage class. |
| typedef sparsetable<value_type, DEFAULT_GROUP_SIZE, value_alloc_type> Table; |
| |
| // Package templated functors with the other types to eliminate memory |
| // needed for storing these zero-size operators. Since ExtractKey and |
| // hasher's operator() might have the same function signature, they |
| // must be packaged in different classes. |
| |
| // KeyInfo stores delete key and packages zero-size functors: |
| // ExtractKey and SetKey. |
| class KeyInfo : public ExtractKey, public SetKey { |
| public: |
| KeyInfo(const ExtractKey& ek, const SetKey& sk) |
| : ExtractKey(ek), SetKey(sk) { |
| } |
| const key_type get_key(const_reference v) const { |
| return ExtractKey::operator()(v); |
| } |
| void set_key(pointer v, const key_type& k) const { |
| SetKey::operator()(v, k); |
| } |
| |
| // TODO(csilvers): make a pointer, and get rid of use_deleted (benchmark!) |
| key_type delkey; |
| }; |
| |
| // Settings contains parameters for growing and shrinking the table. |
| // It also packages zero-size functors (ie. hasher and key_equal). |
| class Settings : public hasher, public key_equal { |
| public: |
| Settings(const hasher& hf, const key_equal& eq) |
| : hasher(hf), |
| key_equal(eq), |
| enlarge_resize_percent(HT_OCCUPANCY_FLT), |
| shrink_resize_percent(HT_EMPTY_FLT), |
| enlarge_threshold(0), |
| shrink_threshold(0) { |
| } |
| size_type hash(const key_type& v) const { |
| return hasher::operator()(v); |
| } |
| bool equals(const key_type& a, const key_type& b) const { |
| return key_equal::operator()(a, b); |
| } |
| |
| float enlarge_resize_percent; // how full before resize |
| float shrink_resize_percent; // how empty before resize |
| size_type enlarge_threshold; // table.size() * enlarge_resize_percent |
| size_type shrink_threshold; // table.size() * shrink_resize_percent |
| }; |
| |
| void reset_thresholds() { |
| settings.enlarge_threshold = static_cast<size_type>( |
| table.size() * settings.enlarge_resize_percent); |
| settings.shrink_threshold = static_cast<size_type>( |
| table.size() * settings.shrink_resize_percent); |
| consider_shrink = false; // whatever caused us to reset already considered |
| } |
| |
| // Utility functions to access the templated operators |
| size_type hash(const key_type& v) const { |
| return settings.hash(v); |
| } |
| bool equals(const key_type& a, const key_type& b) const { |
| return settings.equals(a, b); |
| } |
| const key_type get_key(const_reference v) const { |
| return key_info.get_key(v); |
| } |
| void set_key(pointer v, const key_type& k) const { |
| key_info.set_key(v, k); |
| } |
| |
| private: |
| // Actual data |
| Settings settings; |
| KeyInfo key_info; |
| bool consider_shrink; // true if we should try to shrink before next insert |
| bool use_deleted; // false until delkey has been set |
| |
| // TODO(giao): Reduce the number of bits for num_ht_copies. It is not |
| // currently used by any application. |
| int num_ht_copies; // a statistics counter incremented every Copy/Move |
| size_type num_deleted; // how many occupied buckets are marked deleted |
| Table table; // holds num_buckets and num_elements too |
| }; |
| |
| |
| // We need a global swap as well |
| template <class V, class K, class HF, class ExK, class SetK, class EqK, class A> |
| inline void swap(sparse_hashtable<V,K,HF,ExK,SetK,EqK,A> &x, |
| sparse_hashtable<V,K,HF,ExK,SetK,EqK,A> &y) { |
| x.swap(y); |
| } |
| |
| #undef JUMP_ |
| |
| template <class V, class K, class HF, class ExK, class SetK, class EqK, class A> |
| const typename sparse_hashtable<V,K,HF,ExK,SetK,EqK,A>::size_type |
| sparse_hashtable<V,K,HF,ExK,SetK,EqK,A>::ILLEGAL_BUCKET; |
| |
| // How full we let the table get before we resize. Knuth says .8 is |
| // good -- higher causes us to probe too much, though saves memory |
| template <class V, class K, class HF, class ExK, class SetK, class EqK, class A> |
| const float sparse_hashtable<V,K,HF,ExK,SetK,EqK,A>::HT_OCCUPANCY_FLT = 0.8f; |
| |
| // How empty we let the table get before we resize lower. |
| // It should be less than OCCUPANCY_FLT / 2 or we thrash resizing |
| template <class V, class K, class HF, class ExK, class SetK, class EqK, class A> |
| const float sparse_hashtable<V,K,HF,ExK,SetK,EqK,A>::HT_EMPTY_FLT |
| = 0.4f * sparse_hashtable<V,K,HF,ExK,SetK,EqK,A>::HT_OCCUPANCY_FLT; |
| |
| _END_GOOGLE_NAMESPACE_ |
| |
| #endif /* _SPARSEHASHTABLE_H_ */ |
