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专业: 计算机应用技术

[求助] PageRank算法代码

谁能帮我讲讲下面这段PageRank算法代码啊，跪求啊。
void update(graphchi_vertex<VertexDataType, EdgeDataType> &v, graphchi_context &ginfo) {
      float sum=0;
      if (ginfo.iteration == 0) {
         /* On first iteration, initialize vertex and out-edges.
            The initialization is important,
            because on every run, GraphChi will modify the data in the edges on disk.
         */
         for(int i=0; i < v.num_outedges(); i++) {
            graphchi_edge<float> * edge = v.outedge(i);
            edge->set_data(1.0 / v.num_outedges());
         }
         v.set_data(RANDOMRESETPROB);
      } else {
         /* Compute the sum of neighbors' weighted pageranks by
            reading from the in-edges. */
         for(int i=0; i < v.num_inedges(); i++) {
            float val = v.inedge(i)->get_data();
            sum += val;
         }

         /* Compute my pagerank */
         float pagerank = RANDOMRESETPROB + (1 - RANDOMRESETPROB) * sum;

         /* Write my pagerank divided by the number of out-edges to
            each of my out-edges. */
         if (v.num_outedges() > 0) {
            float pagerankcont = pagerank / v.num_outedges();
            for(int i=0; i < v.num_outedges(); i++) {
                  graphchi_edge<float> * edge = v.outedge(i);
                  edge->set_data(pagerankcont);
            }
         }

         /* Keep track of the progression of the computation.
            GraphChi engine writes a file filename.deltalog. */
         ginfo.log_change(std::abs(pagerank - v.get_data()));

         /* Set my new pagerank as the vertex value */
         v.set_data(pagerank);
      }
}

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