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Current view: top level - include/llvm/ADT - SparseSet.h (source / functions) Hit Total Coverage
Test: llvm-toolchain.info Lines: 28 28 100.0 %
Date: 2018-07-13 00:08:38 Functions: 51 51 100.0 %
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       1             : //===- llvm/ADT/SparseSet.h - Sparse set ------------------------*- C++ -*-===//
       2             : //
       3             : //                     The LLVM Compiler Infrastructure
       4             : //
       5             : // This file is distributed under the University of Illinois Open Source
       6             : // License. See LICENSE.TXT for details.
       7             : //
       8             : //===----------------------------------------------------------------------===//
       9             : //
      10             : // This file defines the SparseSet class derived from the version described in
      11             : // Briggs, Torczon, "An efficient representation for sparse sets", ACM Letters
      12             : // on Programming Languages and Systems, Volume 2 Issue 1-4, March-Dec.  1993.
      13             : //
      14             : // A sparse set holds a small number of objects identified by integer keys from
      15             : // a moderately sized universe. The sparse set uses more memory than other
      16             : // containers in order to provide faster operations.
      17             : //
      18             : //===----------------------------------------------------------------------===//
      19             : 
      20             : #ifndef LLVM_ADT_SPARSESET_H
      21             : #define LLVM_ADT_SPARSESET_H
      22             : 
      23             : #include "llvm/ADT/STLExtras.h"
      24             : #include "llvm/ADT/SmallVector.h"
      25             : #include "llvm/Support/Allocator.h"
      26             : #include <cassert>
      27             : #include <cstdint>
      28             : #include <cstdlib>
      29             : #include <limits>
      30             : #include <utility>
      31             : 
      32             : namespace llvm {
      33             : 
      34             : /// SparseSetValTraits - Objects in a SparseSet are identified by keys that can
      35             : /// be uniquely converted to a small integer less than the set's universe. This
      36             : /// class allows the set to hold values that differ from the set's key type as
      37             : /// long as an index can still be derived from the value. SparseSet never
      38             : /// directly compares ValueT, only their indices, so it can map keys to
      39             : /// arbitrary values. SparseSetValTraits computes the index from the value
      40             : /// object. To compute the index from a key, SparseSet uses a separate
      41             : /// KeyFunctorT template argument.
      42             : ///
      43             : /// A simple type declaration, SparseSet<Type>, handles these cases:
      44             : /// - unsigned key, identity index, identity value
      45             : /// - unsigned key, identity index, fat value providing getSparseSetIndex()
      46             : ///
      47             : /// The type declaration SparseSet<Type, UnaryFunction> handles:
      48             : /// - unsigned key, remapped index, identity value (virtual registers)
      49             : /// - pointer key, pointer-derived index, identity value (node+ID)
      50             : /// - pointer key, pointer-derived index, fat value with getSparseSetIndex()
      51             : ///
      52             : /// Only other, unexpected cases require specializing SparseSetValTraits.
      53             : ///
      54             : /// For best results, ValueT should not require a destructor.
      55             : ///
      56             : template<typename ValueT>
      57             : struct SparseSetValTraits {
      58             :   static unsigned getValIndex(const ValueT &Val) {
      59    92150203 :     return Val.getSparseSetIndex();
      60             :   }
      61             : };
      62             : 
      63             : /// SparseSetValFunctor - Helper class for selecting SparseSetValTraits. The
      64             : /// generic implementation handles ValueT classes which either provide
      65             : /// getSparseSetIndex() or specialize SparseSetValTraits<>.
      66             : ///
      67             : template<typename KeyT, typename ValueT, typename KeyFunctorT>
      68             : struct SparseSetValFunctor {
      69             :   unsigned operator()(const ValueT &Val) const {
      70             :     return SparseSetValTraits<ValueT>::getValIndex(Val);
      71             :   }
      72             : };
      73             : 
      74             : /// SparseSetValFunctor<KeyT, KeyT> - Helper class for the common case of
      75             : /// identity key/value sets.
      76             : template<typename KeyT, typename KeyFunctorT>
      77             : struct SparseSetValFunctor<KeyT, KeyT, KeyFunctorT> {
      78             :   unsigned operator()(const KeyT &Key) const {
      79             :     return KeyFunctorT()(Key);
      80             :   }
      81             : };
      82             : 
      83             : /// SparseSet - Fast set implmentation for objects that can be identified by
      84             : /// small unsigned keys.
      85             : ///
      86             : /// SparseSet allocates memory proportional to the size of the key universe, so
      87             : /// it is not recommended for building composite data structures.  It is useful
      88             : /// for algorithms that require a single set with fast operations.
      89             : ///
      90             : /// Compared to DenseSet and DenseMap, SparseSet provides constant-time fast
      91             : /// clear() and iteration as fast as a vector.  The find(), insert(), and
      92             : /// erase() operations are all constant time, and typically faster than a hash
      93             : /// table.  The iteration order doesn't depend on numerical key values, it only
      94             : /// depends on the order of insert() and erase() operations.  When no elements
      95             : /// have been erased, the iteration order is the insertion order.
      96             : ///
      97             : /// Compared to BitVector, SparseSet<unsigned> uses 8x-40x more memory, but
      98             : /// offers constant-time clear() and size() operations as well as fast
      99             : /// iteration independent on the size of the universe.
     100             : ///
     101             : /// SparseSet contains a dense vector holding all the objects and a sparse
     102             : /// array holding indexes into the dense vector.  Most of the memory is used by
     103             : /// the sparse array which is the size of the key universe.  The SparseT
     104             : /// template parameter provides a space/speed tradeoff for sets holding many
     105             : /// elements.
     106             : ///
     107             : /// When SparseT is uint32_t, find() only touches 2 cache lines, but the sparse
     108             : /// array uses 4 x Universe bytes.
     109             : ///
     110             : /// When SparseT is uint8_t (the default), find() touches up to 2+[N/256] cache
     111             : /// lines, but the sparse array is 4x smaller.  N is the number of elements in
     112             : /// the set.
     113             : ///
     114             : /// For sets that may grow to thousands of elements, SparseT should be set to
     115             : /// uint16_t or uint32_t.
     116             : ///
     117             : /// @tparam ValueT      The type of objects in the set.
     118             : /// @tparam KeyFunctorT A functor that computes an unsigned index from KeyT.
     119             : /// @tparam SparseT     An unsigned integer type. See above.
     120             : ///
     121             : template<typename ValueT,
     122             :          typename KeyFunctorT = identity<unsigned>,
     123             :          typename SparseT = uint8_t>
     124             : class SparseSet {
     125             :   static_assert(std::numeric_limits<SparseT>::is_integer &&
     126             :                 !std::numeric_limits<SparseT>::is_signed,
     127             :                 "SparseT must be an unsigned integer type");
     128             : 
     129             :   using KeyT = typename KeyFunctorT::argument_type;
     130             :   using DenseT = SmallVector<ValueT, 8>;
     131             :   using size_type = unsigned;
     132             :   DenseT Dense;
     133             :   SparseT *Sparse = nullptr;
     134             :   unsigned Universe = 0;
     135             :   KeyFunctorT KeyIndexOf;
     136             :   SparseSetValFunctor<KeyT, ValueT, KeyFunctorT> ValIndexOf;
     137             : 
     138             : public:
     139             :   using value_type = ValueT;
     140             :   using reference = ValueT &;
     141             :   using const_reference = const ValueT &;
     142             :   using pointer = ValueT *;
     143             :   using const_pointer = const ValueT *;
     144             : 
     145     1739110 :   SparseSet() = default;
     146             :   SparseSet(const SparseSet &) = delete;
     147             :   SparseSet &operator=(const SparseSet &) = delete;
     148     3477390 :   ~SparseSet() { free(Sparse); }
     149             : 
     150             :   /// setUniverse - Set the universe size which determines the largest key the
     151             :   /// set can hold.  The universe must be sized before any elements can be
     152             :   /// added.
     153             :   ///
     154             :   /// @param U Universe size. All object keys must be less than U.
     155             :   ///
     156     1279568 :   void setUniverse(unsigned U) {
     157             :     // It's not hard to resize the universe on a non-empty set, but it doesn't
     158             :     // seem like a likely use case, so we can add that code when we need it.
     159             :     assert(empty() && "Can only resize universe on an empty map");
     160             :     // Hysteresis prevents needless reallocations.
     161     1279568 :     if (U >= Universe/4 && U <= Universe)
     162             :       return;
     163      628304 :     free(Sparse);
     164             :     // The Sparse array doesn't actually need to be initialized, so malloc
     165             :     // would be enough here, but that will cause tools like valgrind to
     166             :     // complain about branching on uninitialized data.
     167      628304 :     Sparse = static_cast<SparseT*>(safe_calloc(U, sizeof(SparseT)));
     168      628304 :     Universe = U;
     169             :   }
     170             : 
     171             :   // Import trivial vector stuff from DenseT.
     172             :   using iterator = typename DenseT::iterator;
     173             :   using const_iterator = typename DenseT::const_iterator;
     174             : 
     175             :   const_iterator begin() const { return Dense.begin(); }
     176             :   const_iterator end() const { return Dense.end(); }
     177             :   iterator begin() { return Dense.begin(); }
     178             :   iterator end() { return Dense.end(); }
     179             : 
     180             :   /// empty - Returns true if the set is empty.
     181             :   ///
     182             :   /// This is not the same as BitVector::empty().
     183             :   ///
     184     2963610 :   bool empty() const { return Dense.empty(); }
     185             : 
     186             :   /// size - Returns the number of elements in the set.
     187             :   ///
     188             :   /// This is not the same as BitVector::size() which returns the size of the
     189             :   /// universe.
     190             :   ///
     191    98857535 :   size_type size() const { return Dense.size(); }
     192             : 
     193             :   /// clear - Clears the set.  This is a very fast constant time operation.
     194             :   ///
     195             :   void clear() {
     196             :     // Sparse does not need to be cleared, see find().
     197             :     Dense.clear();
     198             :   }
     199             : 
     200             :   /// findIndex - Find an element by its index.
     201             :   ///
     202             :   /// @param   Idx A valid index to find.
     203             :   /// @returns An iterator to the element identified by key, or end().
     204             :   ///
     205             :   iterator findIndex(unsigned Idx) {
     206             :     assert(Idx < Universe && "Key out of range");
     207             :     const unsigned Stride = std::numeric_limits<SparseT>::max() + 1u;
     208   278447736 :     for (unsigned i = Sparse[Idx], e = size(); i < e; i += Stride) {
     209   132678844 :       const unsigned FoundIdx = ValIndexOf(Dense[i]);
     210             :       assert(FoundIdx < Universe && "Invalid key in set. Did object mutate?");
     211    73224513 :       if (Idx == FoundIdx)
     212             :         return begin() + i;
     213             :       // Stride is 0 when SparseT >= unsigned.  We don't need to loop.
     214             :       if (!Stride)
     215             :         break;
     216             :     }
     217             :     return end();
     218             :   }
     219             : 
     220             :   /// find - Find an element by its key.
     221             :   ///
     222             :   /// @param   Key A valid key to find.
     223             :   /// @returns An iterator to the element identified by key, or end().
     224             :   ///
     225             :   iterator find(const KeyT &Key) {
     226             :     return findIndex(KeyIndexOf(Key));
     227             :   }
     228             : 
     229             :   const_iterator find(const KeyT &Key) const {
     230             :     return const_cast<SparseSet*>(this)->findIndex(KeyIndexOf(Key));
     231             :   }
     232             : 
     233             :   /// count - Returns 1 if this set contains an element identified by Key,
     234             :   /// 0 otherwise.
     235             :   ///
     236             :   size_type count(const KeyT &Key) const {
     237         702 :     return find(Key) == end() ? 0 : 1;
     238             :   }
     239             : 
     240             :   /// insert - Attempts to insert a new element.
     241             :   ///
     242             :   /// If Val is successfully inserted, return (I, true), where I is an iterator
     243             :   /// pointing to the newly inserted element.
     244             :   ///
     245             :   /// If the set already contains an element with the same key as Val, return
     246             :   /// (I, false), where I is an iterator pointing to the existing element.
     247             :   ///
     248             :   /// Insertion invalidates all iterators.
     249             :   ///
     250    48590566 :   std::pair<iterator, bool> insert(const ValueT &Val) {
     251    43720922 :     unsigned Idx = ValIndexOf(Val);
     252             :     iterator I = findIndex(Idx);
     253    48590566 :     if (I != end())
     254             :       return std::make_pair(I, false);
     255    35269894 :     Sparse[Idx] = size();
     256    35269894 :     Dense.push_back(Val);
     257    35269894 :     return std::make_pair(end() - 1, true);
     258             :   }
     259             : 
     260             :   /// array subscript - If an element already exists with this key, return it.
     261             :   /// Otherwise, automatically construct a new value from Key, insert it,
     262             :   /// and return the newly inserted element.
     263             :   ValueT &operator[](const KeyT &Key) {
     264        6119 :     return *insert(ValueT(Key)).first;
     265             :   }
     266             : 
     267             :   ValueT pop_back_val() {
     268             :     // Sparse does not need to be cleared, see find().
     269             :     return Dense.pop_back_val();
     270             :   }
     271             : 
     272             :   /// erase - Erases an existing element identified by a valid iterator.
     273             :   ///
     274             :   /// This invalidates all iterators, but erase() returns an iterator pointing
     275             :   /// to the next element.  This makes it possible to erase selected elements
     276             :   /// while iterating over the set:
     277             :   ///
     278             :   ///   for (SparseSet::iterator I = Set.begin(); I != Set.end();)
     279             :   ///     if (test(*I))
     280             :   ///       I = Set.erase(I);
     281             :   ///     else
     282             :   ///       ++I;
     283             :   ///
     284             :   /// Note that end() changes when elements are erased, unlike std::list.
     285             :   ///
     286             :   iterator erase(iterator I) {
     287             :     assert(unsigned(I - begin()) < size() && "Invalid iterator");
     288    12521260 :     if (I != end() - 1) {
     289     9677097 :       *I = Dense.back();
     290     9677040 :       unsigned BackIdx = ValIndexOf(Dense.back());
     291             :       assert(BackIdx < Universe && "Invalid key in set. Did object mutate?");
     292    10926701 :       Sparse[BackIdx] = I - begin();
     293             :     }
     294             :     // This depends on SmallVector::pop_back() not invalidating iterators.
     295             :     // std::vector::pop_back() doesn't give that guarantee.
     296             :     Dense.pop_back();
     297             :     return I;
     298             :   }
     299             : 
     300             :   /// erase - Erases an element identified by Key, if it exists.
     301             :   ///
     302             :   /// @param   Key The key identifying the element to erase.
     303             :   /// @returns True when an element was erased, false if no element was found.
     304             :   ///
     305    30765092 :   bool erase(const KeyT &Key) {
     306    30765092 :     iterator I = find(Key);
     307    30765092 :     if (I == end())
     308             :       return false;
     309             :     erase(I);
     310             :     return true;
     311             :   }
     312             : };
     313             : 
     314             : } // end namespace llvm
     315             : 
     316             : #endif // LLVM_ADT_SPARSESET_H

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