bc comments

bc.cc

@@ -17,10 +17,35 @@
 #include "timer.h"
 
 
+/*
+GAP Benchmark Suite
+Kernel: Betweenness Centrality (BC)
+Author: Scott Beamer
+
+Will return array of approx betweenness centrality scores for each vertex
+
+This BC implementation makes use of the Brandes [1] algorithm with
+implementation optimizations from Madduri et al. [2]. It is only an approximate
+because it does not compute the paths from every start vertex, but only a small
+subset of them. Additionally, the scores are normalized to the range [0,1].
+
+As an optimization to save memory, this implementation uses a Bitmap to hold
+succ (list of successors) found during the BFS phase that are used in the back-
+propagation phase.
+
+[1] Ulrik Brandes. "A faster algorithm for betweenness centrality." Journal of
+    Mathematical Sociology, 25(2):163–177, 2001.
+
+[2] Kamesh Madduri, David Ediger, Karl Jiang, David A Bader, and Daniel
+    Chavarria-Miranda. "A faster parallel algorithm and efficient multithreaded
+    implementations for evaluating betweenness centrality on massive datasets."
+    International Symposium on Parallel & Distributed Processing (IPDPS), 2009.
+*/
+
+
 using namespace std;
 typedef float ScoreT;
 
-
 void PBFS(const Graph &g, NodeID source, pvector<NodeID> &path_counts,
     Bitmap &succ, vector<SlidingQueue<NodeID>::iterator> &depth_index,
     SlidingQueue<NodeID> &queue) {