PDS_TriangleCount/src/v3.cpp

/*!
 * \file    v3.cpp
 * \brief   vv3 part of the exercise.
 *
 * \author
 *    Christos Choutouridis AEM:8997
 *    <cchoutou@ece.auth.gr>
 */

#include <iostream>
#include <random>
#include <v3.h>

namespace v3 {

using index_t  = typename matrix::indexType;
using value_t  = typename matrix::dataType;

/*!
 * A naive triangle counting algorithm
 * \param A    The adjacency matrix
 * \return     The number of triangles
 */
std::vector<value_t> triang_v(matrix& A) {
   std::vector<value_t> c(A.size());

   for (int i=0 ; i<A.size() ; ++i) {
      for (auto j = A.getCol(i); j.index() != j.end() ; ++j)               // j list all the edges with i
         for (auto k = A.getCol(j.index()); k.index() != k.end() ; ++k)    // k list all the edges with j
            for (auto ii = A.getCol(i) ; ii.index() <= k.index() ; ++ii)   // search for i-k edge (this could be binary search)
               if (ii.index() == k.index())  ++c[i];
   }
   return c;
}

value_t sum (std::vector<value_t>& v) {
   value_t s =0;
   for (auto& it : v)
      s += it;
   return s;
}

value_t triang_count (matrix& A) {
   auto v = triang_v(A);
   return sum(v);
}

}