Add a swap function.

cxxmph/mph_index.cc

@@ -43,10 +43,10 @@ MPHIndex::~MPHIndex() {
 }
 
 void MPHIndex::clear() {
-  delete [] ranktable_;
-  ranktable_ = NULL;
-  ranktable_size_ = 0;
-  // TODO(davi) implement me
+  std::vector<uint32_t> empty_ranktable;
+  ranktable_.swap(empty_ranktable);
+  dynamic_2bitset empty_g;
+  g_.swap(empty_g);
 }
 
 bool MPHIndex::GenerateQueue(
@@ -159,17 +159,14 @@ void MPHIndex::Assigning(
 void MPHIndex::Ranking() {
   uint32_t nbytes_total = static_cast<uint32_t>(ceil(n_ / 4.0));
   uint32_t size = k_ >> 2U;
-  ranktable_size_ = static_cast<uint32_t>(
+  uint32_t ranktable_size = static_cast<uint32_t>(
       ceil(n_ / static_cast<double>(k_)));
-  delete [] ranktable_;
-  ranktable_ = NULL;
-  uint32_t* ranktable = new uint32_t[ranktable_size_];
-  memset(ranktable, 0, ranktable_size_*sizeof(uint32_t));
+  vector<uint32_t> ranktable(ranktable_size);
   uint32_t offset = 0;
   uint32_t count = 0;
   uint32_t i = 1;
   while (1) {
-    if (i == ranktable_size_) break;
+    if (i == ranktable.size()) break;
     uint32_t nbytes = size < nbytes_total ? size : nbytes_total;
     for (uint32_t j = 0; j < nbytes; ++j) {
       count += kBdzLookupIndex[g_.data()[offset + j]];
@@ -179,11 +176,11 @@ void MPHIndex::Ranking() {
     nbytes_total -= size;
     ++i;
   }
-  ranktable_ = ranktable;
+  ranktable_.swap(ranktable);
 }
 
 uint32_t MPHIndex::Rank(uint32_t vertex) const {
-  if (!ranktable_size_) return 0;
+  if (ranktable_.empty()) return 0;
   uint32_t index = vertex >> b_;
   uint32_t base_rank = ranktable_[index];
   uint32_t beg_idx_v = index << b_;
@@ -211,4 +208,22 @@ uint32_t MPHIndex::Rank(uint32_t vertex) const {
   return base_rank;
 }
 
+void MPHIndex::swap(std::vector<uint32_t>& params, dynamic_2bitset& g, std::vector<uint32_t>& ranktable) {
+  params.resize(12);
+  uint32_t rounded_c = c_ * 1000 * 1000;
+  std::swap(params[0], rounded_c);
+  c_ = static_cast<double>(rounded_c) / 1000 / 1000;
+  std::swap(params[1], m_);
+  std::swap(params[2], n_);
+  std::swap(params[3], k_);
+  uint32_t uint32_square = static_cast<uint32_t>(square_);
+  std::swap(params[4], uint32_square);
+  square_ = uint32_square;
+  std::swap(params[5], hash_seed_[0]);
+  std::swap(params[6], hash_seed_[1]);
+  std::swap(params[7], hash_seed_[2]);
+  g.swap(g_);
+  ranktable.swap(ranktable_);
+}
+
 }  // namespace cxxmph

cxxmph/mph_index.h

@@ -45,8 +45,7 @@ namespace cxxmph {
 class MPHIndex {
  public:
   MPHIndex(bool square = false, double c = 1.23, uint8_t b = 7) :
-      c_(c), b_(b), m_(0), n_(0), k_(0), square_(square), r_(1), g_(8, true),
-      ranktable_(NULL), ranktable_size_(0) {
+      c_(c), b_(b), m_(0), n_(0), k_(0), square_(square), r_(1), g_(8, true) {
     nest_displacement_[0] = 0;
     nest_displacement_[1] = r_;
     nest_displacement_[2] = (r_ << 1);
@@ -63,7 +62,7 @@ class MPHIndex {
   void clear();
 
   // Advanced users functions. Please avoid unless you know what you are doing.
-  uint32_t perfect_hash_size() const { return n_; } 
+  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;  // way faster than the minimal
   template <class SeededHashFcn, class Key>  // must agree with Reset
@@ -72,6 +71,11 @@ class MPHIndex {
   template <class SeededHashFcn, class Key>  // must agree with Reset
   uint32_t minimal_perfect_hash(const Key& x) const;
 
+  // Experimental api to use as a serialization building block.
+  // Since this signature exposes some implementation details, expect it to
+  // change.
+  void swap(std::vector<uint32_t>& params, dynamic_2bitset& g, std::vector<uint32_t>& ranktable);
+
  private:
   template <class SeededHashFcn, class ForwardIterator>
   bool Mapping(ForwardIterator begin, ForwardIterator end,
@@ -85,7 +89,7 @@ class MPHIndex {
 
   // Algorithm parameters
   // Perfect hash function density. If this was a 2graph,
-  // then probability of having an acyclic graph would be 
+  // then probability of having an acyclic graph would be
   // sqrt(1-(2/c)^2). See section 3 for details.
   // http://www.it-c.dk/people/pagh/papers/simpleperf.pdf
   double c_;
@@ -107,8 +111,7 @@ class MPHIndex {
   dynamic_2bitset g_;
   uint8_t threebit_mod3[10];  // speed up mod3 calculation for 3bit ints
   // The table used for the rank step of the minimal perfect hash function
-  const uint32_t* ranktable_;
-  uint32_t ranktable_size_;
+  std::vector<uint32_t> ranktable_;
   // The selected hash seed triplet for finding the edges in the minimal
   // perfect hash function graph.
   uint32_t hash_seed_[3];
@@ -142,7 +145,7 @@ bool MPHIndex::Reset(
   std::vector<TriGraph::Edge> edges;
   std::vector<uint32_t> queue;
   while (1) {
-    // cerr << "Iterations missing: " << iterations << endl;
+    cerr << "Iterations missing: " << iterations << endl;
     for (int i = 0; i < 3; ++i) hash_seed_[i] = random();
     if (Mapping<SeededHashFcn>(begin, end, &edges, &queue)) break;
     else --iterations;
@@ -160,7 +163,7 @@ bool MPHIndex::Mapping(
     ForwardIterator begin, ForwardIterator end,
     std::vector<TriGraph::Edge>* edges, std::vector<uint32_t>* queue) {
   TriGraph graph(n_, m_);
-  for (ForwardIterator it = begin; it != end; ++it) { 
+  for (ForwardIterator it = begin; it != end; ++it) {
     h128 h = SeededHashFcn().hash128(*it, hash_seed_[0]);
     // for (int i = 0; i < 3; ++i) h[i] = SeededHashFcn()(*it, hash_seed_[i]);
     uint32_t v0 = h[0] % r_;

cxxmph/mph_index_test.cc

@@ -34,6 +34,16 @@ int main(int argc, char** argv) {
   sort(ids.begin(), ids.end());
   for (vector<int>::size_type i = 0; i < ids.size(); ++i) assert(ids[i] == static_cast<vector<int>::value_type>(i));
 
+  // Test serialization
+  vector<uint32_t> params;
+  dynamic_2bitset g;
+  vector<uint32_t> ranktable;
+  mph_index.swap(params, g, ranktable);
+  assert(mph_index.size() == 0);
+  mph_index.swap(params, g, ranktable);
+  assert(mph_index.size() == ids.size());
+  for (vector<int>::size_type i = 0; i < ids.size(); ++i) assert(ids[i] == static_cast<vector<int>::value_type>(i));
+
   FlexibleMPHIndex<false, true, int64_t, seeded_hash<std::hash<int64_t>>::hash_function> square_empty;
   auto id = square_empty.index(1);
   FlexibleMPHIndex<false, false, int64_t, seeded_hash<std::hash<int64_t>>::hash_function> unordered_empty;