lemon-1.1: comparison lemon/circulation.h

equal deleted inserted replaced

-:6b2b32df34e3
+:35e38c53a9ec
 #ifndef LEMON_CIRCULATION_H
 #define LEMON_CIRCULATION_H
 #include <lemon/tolerance.h>
 #include <lemon/elevator.h>
+#include <limits>
 ///\ingroup max_flow
 ///\file
 ///\brief Push-relabel algorithm for finding a feasible circulation.
 ///
 are given for the flow values on the arcs and lower bounds are
 given for the difference between the outgoing and incoming flow
 at the nodes.
 The exact formulation of this problem is the following.
-Let \f$G=(V,A)\f$ be a digraph,
+Let \f$G=(V,A)\f$ be a digraph, \f$lower: A\rightarrow\mathbf{R}\f$
-\f$lower, upper: A\rightarrow\mathbf{R}^+_0\f$ denote the lower and
+\f$upper: A\rightarrow\mathbf{R}\cup\{\infty\}\f$ denote the lower and
-upper bounds on the arcs, for which \f$0 \leq lower(uv) \leq upper(uv)\f$
+upper bounds on the arcs, for which \f$lower(uv) \leq upper(uv)\f$
 holds for all \f$uv\in A\f$, and \f$sup: V\rightarrow\mathbf{R}\f$
 denotes the signed supply values of the nodes.
 If \f$sup(u)>0\f$, then \f$u\f$ is a supply node with \f$sup(u)\f$
 supply, if \f$sup(u)<0\f$, then \f$u\f$ is a demand node with
 \f$-sup(u)\f$ demand.
-A feasible circulation is an \f$f: A\rightarrow\mathbf{R}^+_0\f$
+A feasible circulation is an \f$f: A\rightarrow\mathbf{R}\f$
 solution of the following problem.
 \f[ \sum_{uv\in A} f(uv) - \sum_{vu\in A} f(vu)
 \geq sup(u) \quad \forall u\in V, \f]
 \f[ lower(uv) \leq f(uv) \leq upper(uv) \quad \forall uv\in A. \f]
 (i.e. the total demand is less than the total supply and all the demands
 have to be satisfied while there could be supplies that are not used),
 then you could easily transform the problem to the above form by reversing
 the direction of the arcs and taking the negative of the supply values
 (e.g. using \ref ReverseDigraph and \ref NegMap adaptors).
+This algorithm either calculates a feasible circulation, or provides
+a \ref barrier() "barrier", which prooves that a feasible soultion
+cannot exist.
 Note that this algorithm also provides a feasible solution for the
 \ref min_cost_flow "minimum cost flow problem".
 \tparam GR The type of the digraph the algorithm runs on.
 }
 private:
+bool checkBoundMaps() {
+for (ArcIt e(_g);e!=INVALID;++e) {
+if (_tol.less((*_up)[e], (*_lo)[e])) return false;
+}
+return true;
+}
 void createStructures() {
 _node_num = _el = countNodes(_g);
 if (!_flow) {
 _flow = Traits::createFlowMap(_g);
 /// Sets the upper bound (capacity) map.
 /// Sets the upper bound (capacity) map.
 /// \return <tt>(*this)</tt>
-Circulation& upperMap(const LowerMap& map) {
+Circulation& upperMap(const UpperMap& map) {
 _up = &map;
 return *this;
 }
 /// Sets the supply map.
 /// Initializes the internal data structures and sets all flow values
 /// to the lower bound.
 void init()
 {
+LEMON_DEBUG(checkBoundMaps(),
+"Upper bounds must be greater or equal to the lower bounds");
 createStructures();
 for(NodeIt n(_g);n!=INVALID;++n) {
 (*_excess)[n] = (*_supply)[n];
 }
 /// Initializes the internal data structures using a greedy approach
 /// to construct the initial solution.
 void greedyInit()
 {
+LEMON_DEBUG(checkBoundMaps(),
+"Upper bounds must be greater or equal to the lower bounds");
 createStructures();
 for(NodeIt n(_g);n!=INVALID;++n) {
 (*_excess)[n] = (*_supply)[n];
 }
 for (ArcIt e(_g);e!=INVALID;++e) {
-if (!_tol.positive((*_excess)[_g.target(e)] + (*_up)[e])) {
+if (!_tol.less(-(*_excess)[_g.target(e)], (*_up)[e])) {
 _flow->set(e, (*_up)[e]);
 (*_excess)[_g.target(e)] += (*_up)[e];
 (*_excess)[_g.source(e)] -= (*_up)[e];
-} else if (_tol.positive((*_excess)[_g.target(e)] + (*_lo)[e])) {
+} else if (_tol.less(-(*_excess)[_g.target(e)], (*_lo)[e])) {
 _flow->set(e, (*_lo)[e]);
 (*_excess)[_g.target(e)] += (*_lo)[e];
 (*_excess)[_g.source(e)] -= (*_lo)[e];
 } else {
 Flow fc = -(*_excess)[_g.target(e)];
 ///\sa barrier()
 ///\sa barrierMap()
 bool checkBarrier() const
 {
 Flow delta=0;
+Flow inf_cap = std::numeric_limits<Flow>::has_infinity ?
+std::numeric_limits<Flow>::infinity() :
+std::numeric_limits<Flow>::max();
 for(NodeIt n(_g);n!=INVALID;++n)
 if(barrier(n))
 delta-=(*_supply)[n];
 for(ArcIt e(_g);e!=INVALID;++e)
 {
 Node s=_g.source(e);
 Node t=_g.target(e);
-if(barrier(s)&&!barrier(t)) delta+=(*_up)[e];
+if(barrier(s)&&!barrier(t)) {
+if (_tol.less(inf_cap - (*_up)[e], delta)) return false;
+delta+=(*_up)[e];
+}
 else if(barrier(t)&&!barrier(s)) delta-=(*_lo)[e];
 }
 return _tol.negative(delta);
 }

changeset 635	72ac25ad276e
parent 603	85cb3aa71cce
child 637	756a5ec551c8