Merge pull request #126 from GraphStreamingProject/range_merge

Supernode: range merge function

include/supernode.h

@@ -37,6 +37,7 @@ class Supernode {
 
 private:
   size_t num_sketches;
+  size_t merged_sketches; // This variable tells us which sketches are good for queries post merge
   size_t sketch_size;
 
   /* collection of logn sketches to query from, since we can't query from one
@@ -112,10 +113,10 @@ class Supernode {
   static int get_max_sketches() { return max_sketches; };
 
   // get number of samples remaining in the Supernode
-  int samples_remaining() { return num_sketches - sample_idx; }
+  int samples_remaining() { return merged_sketches - sample_idx; }
 
   inline bool out_of_queries() {
-    return sample_idx >= num_sketches;
+    return sample_idx >= merged_sketches;
   }
 
   inline int curr_idx() {
@@ -158,6 +159,16 @@ class Supernode {
    */
   void merge(Supernode& other);
 
+  /**
+   * In-place range merge function. Updates the caller Supernode.
+   * The range merge only merges some of the Sketches
+   * This function should only be used if you know what you're doing
+   * @param other       Supernode to merge into caller
+   * @param start_idx   Index of first Sketch to merge
+   * @param num_merge   How many sketches to merge
+   */
+  void range_merge(Supernode& other, size_t start_idx, size_t num_merge);
+
   /**
    * Insert or delete an (encoded) edge into the supernode. Guaranteed to be
    * processed BEFORE Boruvka starts.

src/supernode.cpp

@@ -8,7 +8,8 @@ size_t Supernode::bytes_size;
 size_t Supernode::serialized_size;
 
 Supernode::Supernode(uint64_t n, uint64_t seed): sample_idx(0),
-               n(n), seed(seed), num_sketches(max_sketches), sketch_size(Sketch::sketchSizeof()) {
+  n(n), seed(seed), num_sketches(max_sketches),
+  merged_sketches(max_sketches), sketch_size(Sketch::sketchSizeof()) {
 
   size_t sketch_width = Sketch::column_gen(Sketch::get_failure_factor());
   // generate num_sketches sketches for each supernode (read: node)
@@ -40,6 +41,7 @@ Supernode::Supernode(uint64_t n, uint64_t seed, std::istream &binary_in) :
   }
   // sample in range [beg, beg + num)
   num_sketches = beg + num;
+  merged_sketches = num_sketches;
   sample_idx = beg;
 
   // create empty sketches, if any
@@ -59,8 +61,9 @@ Supernode::Supernode(uint64_t n, uint64_t seed, std::istream &binary_in) :
   }
 }
 
-Supernode::Supernode(const Supernode& s) : sample_idx(s.sample_idx), n(s.n),
-    seed(s.seed), num_sketches(s.num_sketches), sketch_size(s.sketch_size) {
+Supernode::Supernode(const Supernode& s) : 
+  sample_idx(s.sample_idx), n(s.n), seed(s.seed), num_sketches(s.num_sketches), 
+  merged_sketches(s.merged_sketches), sketch_size(s.sketch_size) {
   for (size_t i = 0; i < num_sketches; ++i) {
     Sketch::makeSketch(get_sketch(i), *s.get_sketch(i));
   }
@@ -82,7 +85,7 @@ Supernode::~Supernode() {
 }
 
 std::pair<Edge, SampleSketchRet> Supernode::sample() {
-  if (sample_idx == num_sketches) throw OutOfQueriesException();
+  if (out_of_queries()) throw OutOfQueriesException();
 
   std::pair<vec_t, SampleSketchRet> query_ret = get_sketch(sample_idx++)->query();
   vec_t non_zero = query_ret.first;
@@ -91,7 +94,7 @@ std::pair<Edge, SampleSketchRet> Supernode::sample() {
 }
 
 std::pair<std::vector<Edge>, SampleSketchRet> Supernode::exhaustive_sample() {
-  if (sample_idx == num_sketches) throw OutOfQueriesException();
+  if (out_of_queries()) throw OutOfQueriesException();
 
   std::pair<std::vector<vec_t>, SampleSketchRet> query_ret = get_sketch(sample_idx++)->exhaustive_query();
   std::vector<Edge> edges(query_ret.first.size());
@@ -104,10 +107,18 @@ std::pair<std::vector<Edge>, SampleSketchRet> Supernode::exhaustive_sample() {
 
 void Supernode::merge(Supernode &other) {
   sample_idx = std::max(sample_idx, other.sample_idx);
-  num_sketches = std::min(num_sketches, other.num_sketches);
-  for (size_t i=sample_idx;i<num_sketches;++i) {
+  merged_sketches = std::min(merged_sketches, other.merged_sketches);
+  for (size_t i = sample_idx; i < merged_sketches; ++i)
+    (*get_sketch(i))+=(*other.get_sketch(i));
+}
+
+void Supernode::range_merge(Supernode& other, size_t start_idx, size_t num_merge) {
+  sample_idx = std::max(sample_idx, other.sample_idx);
+  // we trust the caller so whatever they tell us goes here
+  // hopefully if the caller is incorrect then this will be caught by out_of_queries()
+  merged_sketches = start_idx + num_merge;
+  for (size_t i = sample_idx; i < merged_sketches; i++)
     (*get_sketch(i))+=(*other.get_sketch(i));
-  }
 }
 
 void Supernode::update(vec_t upd) {