/usr/include/polymake/node_edge_incidences.h is in libpolymake-dev-common 3.2r2-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 | /* Copyright (c) 1997-2018
Ewgenij Gawrilow, Michael Joswig (Technische Universitaet Berlin, Germany)
http://www.polymake.org
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2, or (at your option) any
later version: http://www.gnu.org/licenses/gpl.txt.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
--------------------------------------------------------------------------------
*/
#ifndef POLYMAKE_NODE_EDGE_INCIDENCES_H
#define POLYMAKE_NODE_EDGE_INCIDENCES_H
#include "polymake/SparseMatrix.h"
#include "polymake/Graph.h"
namespace pm {
// the node-edge incidence matrix of a directed graph is totally unimodular
template <typename Coord, typename Graph> inline
SparseMatrix<Coord> node_edge_incidences(const GenericGraph<Graph, graph::Directed>& G)
{
SparseMatrix<Coord> ne(G.top().nodes(), G.top().edges());
int k=0;
for (typename Entire< Edges<Graph> >::const_iterator e=entire(edges(G)); !e.at_end(); ++e, ++k) {
ne(e.to_node(), k)=1;
ne(e.from_node(),k)=-1;
}
return ne;
}
// this is the undirected case
// the node-edge incidence matrix of a /bipartite/ graph is also totally unimodular
template <typename Coord, typename Graph> inline
SparseMatrix<Coord> node_edge_incidences(const GenericGraph<Graph, graph::Undirected>& G)
{
SparseMatrix<Coord> ne(G.top().nodes(), G.top().edges());
int k=0;
for (typename Entire< Edges<Graph> >::const_iterator e=entire(edges(G)); !e.at_end(); ++e, ++k) {
ne(e.to_node(), k)=1;
ne(e.from_node(),k)=1;
}
return ne;
}
}
namespace polymake {
using pm::node_edge_incidences;
}
#endif // POLYMAKE_NODE_EDGE_INCIDENCES_H
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