1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/src/lemon/preflow.h Wed Sep 29 15:30:04 2004 +0000
1.3 @@ -0,0 +1,819 @@
1.4 +/* -*- C++ -*-
1.5 + * src/lemon/preflow.h - Part of LEMON, a generic C++ optimization library
1.6 + *
1.7 + * Copyright (C) 2004 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
1.8 + * (Egervary Combinatorial Optimization Research Group, EGRES).
1.9 + *
1.10 + * Permission to use, modify and distribute this software is granted
1.11 + * provided that this copyright notice appears in all copies. For
1.12 + * precise terms see the accompanying LICENSE file.
1.13 + *
1.14 + * This software is provided "AS IS" with no warranty of any kind,
1.15 + * express or implied, and with no claim as to its suitability for any
1.16 + * purpose.
1.17 + *
1.18 + */
1.19 +
1.20 +#ifndef LEMON_PREFLOW_H
1.21 +#define LEMON_PREFLOW_H
1.22 +
1.23 +#include <vector>
1.24 +#include <queue>
1.25 +
1.26 +#include <lemon/invalid.h>
1.27 +#include <lemon/maps.h>
1.28 +
1.29 +/// \file
1.30 +/// \ingroup flowalgs
1.31 +/// Implementation of the preflow algorithm.
1.32 +
1.33 +namespace lemon {
1.34 +
1.35 + /// \addtogroup flowalgs
1.36 + /// @{
1.37 +
1.38 + ///%Preflow algorithms class.
1.39 +
1.40 + ///This class provides an implementation of the \e preflow \e
1.41 + ///algorithm producing a flow of maximum value in a directed
1.42 + ///graph. The preflow algorithms are the fastest max flow algorithms
1.43 + ///up to now. The \e source node, the \e target node, the \e
1.44 + ///capacity of the edges and the \e starting \e flow value of the
1.45 + ///edges should be passed to the algorithm through the
1.46 + ///constructor. It is possible to change these quantities using the
1.47 + ///functions \ref setSource, \ref setTarget, \ref setCap and \ref
1.48 + ///setFlow.
1.49 + ///
1.50 + ///After running \ref lemon::Preflow::phase1() "phase1()"
1.51 + ///or \ref lemon::Preflow::run() "run()", the maximal flow
1.52 + ///value can be obtained by calling \ref flowValue(). The minimum
1.53 + ///value cut can be written into a <tt>bool</tt> node map by
1.54 + ///calling \ref minCut(). (\ref minMinCut() and \ref maxMinCut() writes
1.55 + ///the inclusionwise minimum and maximum of the minimum value cuts,
1.56 + ///resp.)
1.57 + ///
1.58 + ///\param Graph The directed graph type the algorithm runs on.
1.59 + ///\param Num The number type of the capacities and the flow values.
1.60 + ///\param CapMap The capacity map type.
1.61 + ///\param FlowMap The flow map type.
1.62 + ///
1.63 + ///\author Jacint Szabo
1.64 + template <typename Graph, typename Num,
1.65 + typename CapMap=typename Graph::template EdgeMap<Num>,
1.66 + typename FlowMap=typename Graph::template EdgeMap<Num> >
1.67 + class Preflow {
1.68 + protected:
1.69 + typedef typename Graph::Node Node;
1.70 + typedef typename Graph::NodeIt NodeIt;
1.71 + typedef typename Graph::EdgeIt EdgeIt;
1.72 + typedef typename Graph::OutEdgeIt OutEdgeIt;
1.73 + typedef typename Graph::InEdgeIt InEdgeIt;
1.74 +
1.75 + typedef typename Graph::template NodeMap<Node> NNMap;
1.76 + typedef typename std::vector<Node> VecNode;
1.77 +
1.78 + const Graph* g;
1.79 + Node s;
1.80 + Node t;
1.81 + const CapMap* capacity;
1.82 + FlowMap* flow;
1.83 + int n; //the number of nodes of G
1.84 +
1.85 + typename Graph::template NodeMap<int> level;
1.86 + typename Graph::template NodeMap<Num> excess;
1.87 +
1.88 + // constants used for heuristics
1.89 + static const int H0=20;
1.90 + static const int H1=1;
1.91 +
1.92 + public:
1.93 +
1.94 + ///Indicates the property of the starting flow map.
1.95 +
1.96 + ///Indicates the property of the starting flow map. The meanings are as follows:
1.97 + ///- \c ZERO_FLOW: constant zero flow
1.98 + ///- \c GEN_FLOW: any flow, i.e. the sum of the in-flows equals to
1.99 + ///the sum of the out-flows in every node except the \e source and
1.100 + ///the \e target.
1.101 + ///- \c PRE_FLOW: any preflow, i.e. the sum of the in-flows is at
1.102 + ///least the sum of the out-flows in every node except the \e source.
1.103 + ///- \c NO_FLOW: indicates an unspecified edge map. \c flow will be
1.104 + ///set to the constant zero flow in the beginning of
1.105 + ///the algorithm in this case.
1.106 + ///
1.107 + enum FlowEnum{
1.108 + NO_FLOW,
1.109 + ZERO_FLOW,
1.110 + GEN_FLOW,
1.111 + PRE_FLOW
1.112 + };
1.113 +
1.114 + ///Indicates the state of the preflow algorithm.
1.115 +
1.116 + ///Indicates the state of the preflow algorithm. The meanings are as follows:
1.117 + ///- \c AFTER_NOTHING: before running the algorithm or at an unspecified state.
1.118 + ///- \c AFTER_PREFLOW_PHASE_1: right after running \c phase1
1.119 + ///- \c AFTER_PREFLOW_PHASE_2: after running \ref phase2()
1.120 + ///
1.121 + enum StatusEnum {
1.122 + AFTER_NOTHING,
1.123 + AFTER_PREFLOW_PHASE_1,
1.124 + AFTER_PREFLOW_PHASE_2
1.125 + };
1.126 +
1.127 + protected:
1.128 + FlowEnum flow_prop;
1.129 + StatusEnum status; // Do not needle this flag only if necessary.
1.130 +
1.131 + public:
1.132 + ///The constructor of the class.
1.133 +
1.134 + ///The constructor of the class.
1.135 + ///\param _G The directed graph the algorithm runs on.
1.136 + ///\param _s The source node.
1.137 + ///\param _t The target node.
1.138 + ///\param _capacity The capacity of the edges.
1.139 + ///\param _flow The flow of the edges.
1.140 + ///Except the graph, all of these parameters can be reset by
1.141 + ///calling \ref setSource, \ref setTarget, \ref setCap and \ref
1.142 + ///setFlow, resp.
1.143 + Preflow(const Graph& _G, Node _s, Node _t,
1.144 + const CapMap& _capacity, FlowMap& _flow) :
1.145 + g(&_G), s(_s), t(_t), capacity(&_capacity),
1.146 + flow(&_flow), n(_G.nodeNum()), level(_G), excess(_G,0),
1.147 + flow_prop(NO_FLOW), status(AFTER_NOTHING) { }
1.148 +
1.149 +
1.150 +
1.151 + ///Runs the preflow algorithm.
1.152 +
1.153 + ///Runs the preflow algorithm.
1.154 + ///
1.155 + void run() {
1.156 + phase1(flow_prop);
1.157 + phase2();
1.158 + }
1.159 +
1.160 + ///Runs the preflow algorithm.
1.161 +
1.162 + ///Runs the preflow algorithm.
1.163 + ///\pre The starting flow map must be
1.164 + /// - a constant zero flow if \c fp is \c ZERO_FLOW,
1.165 + /// - an arbitrary flow if \c fp is \c GEN_FLOW,
1.166 + /// - an arbitrary preflow if \c fp is \c PRE_FLOW,
1.167 + /// - any map if \c fp is NO_FLOW.
1.168 + ///If the starting flow map is a flow or a preflow then
1.169 + ///the algorithm terminates faster.
1.170 + void run(FlowEnum fp) {
1.171 + flow_prop=fp;
1.172 + run();
1.173 + }
1.174 +
1.175 + ///Runs the first phase of the preflow algorithm.
1.176 +
1.177 + ///The preflow algorithm consists of two phases, this method runs
1.178 + ///the first phase. After the first phase the maximum flow value
1.179 + ///and a minimum value cut can already be computed, though a
1.180 + ///maximum flow is not yet obtained. So after calling this method
1.181 + ///\ref flowValue returns the value of a maximum flow and \ref
1.182 + ///minCut returns a minimum cut.
1.183 + ///\warning \ref minMinCut and \ref maxMinCut do not give minimum
1.184 + ///value cuts unless calling \ref phase2.
1.185 + ///\pre The starting flow must be
1.186 + ///- a constant zero flow if \c fp is \c ZERO_FLOW,
1.187 + ///- an arbitary flow if \c fp is \c GEN_FLOW,
1.188 + ///- an arbitary preflow if \c fp is \c PRE_FLOW,
1.189 + ///- any map if \c fp is NO_FLOW.
1.190 + void phase1(FlowEnum fp)
1.191 + {
1.192 + flow_prop=fp;
1.193 + phase1();
1.194 + }
1.195 +
1.196 +
1.197 + ///Runs the first phase of the preflow algorithm.
1.198 +
1.199 + ///The preflow algorithm consists of two phases, this method runs
1.200 + ///the first phase. After the first phase the maximum flow value
1.201 + ///and a minimum value cut can already be computed, though a
1.202 + ///maximum flow is not yet obtained. So after calling this method
1.203 + ///\ref flowValue returns the value of a maximum flow and \ref
1.204 + ///minCut returns a minimum cut.
1.205 + ///\warning \ref minCut(), \ref minMinCut() and \ref maxMinCut() do not
1.206 + ///give minimum value cuts unless calling \ref phase2().
1.207 + void phase1()
1.208 + {
1.209 + int heur0=(int)(H0*n); //time while running 'bound decrease'
1.210 + int heur1=(int)(H1*n); //time while running 'highest label'
1.211 + int heur=heur1; //starting time interval (#of relabels)
1.212 + int numrelabel=0;
1.213 +
1.214 + bool what_heur=1;
1.215 + //It is 0 in case 'bound decrease' and 1 in case 'highest label'
1.216 +
1.217 + bool end=false;
1.218 + //Needed for 'bound decrease', true means no active
1.219 + //nodes are above bound b.
1.220 +
1.221 + int k=n-2; //bound on the highest level under n containing a node
1.222 + int b=k; //bound on the highest level under n of an active node
1.223 +
1.224 + VecNode first(n, INVALID);
1.225 + NNMap next(*g, INVALID);
1.226 +
1.227 + NNMap left(*g, INVALID);
1.228 + NNMap right(*g, INVALID);
1.229 + VecNode level_list(n,INVALID);
1.230 + //List of the nodes in level i<n, set to n.
1.231 +
1.232 + preflowPreproc(first, next, level_list, left, right);
1.233 +
1.234 + //Push/relabel on the highest level active nodes.
1.235 + while ( true ) {
1.236 + if ( b == 0 ) {
1.237 + if ( !what_heur && !end && k > 0 ) {
1.238 + b=k;
1.239 + end=true;
1.240 + } else break;
1.241 + }
1.242 +
1.243 + if ( first[b]==INVALID ) --b;
1.244 + else {
1.245 + end=false;
1.246 + Node w=first[b];
1.247 + first[b]=next[w];
1.248 + int newlevel=push(w, next, first);
1.249 + if ( excess[w] > 0 ) relabel(w, newlevel, first, next, level_list,
1.250 + left, right, b, k, what_heur);
1.251 +
1.252 + ++numrelabel;
1.253 + if ( numrelabel >= heur ) {
1.254 + numrelabel=0;
1.255 + if ( what_heur ) {
1.256 + what_heur=0;
1.257 + heur=heur0;
1.258 + end=false;
1.259 + } else {
1.260 + what_heur=1;
1.261 + heur=heur1;
1.262 + b=k;
1.263 + }
1.264 + }
1.265 + }
1.266 + }
1.267 + flow_prop=PRE_FLOW;
1.268 + status=AFTER_PREFLOW_PHASE_1;
1.269 + }
1.270 + // Heuristics:
1.271 + // 2 phase
1.272 + // gap
1.273 + // list 'level_list' on the nodes on level i implemented by hand
1.274 + // stack 'active' on the active nodes on level i
1.275 + // runs heuristic 'highest label' for H1*n relabels
1.276 + // runs heuristic 'bound decrease' for H0*n relabels, starts with 'highest label'
1.277 + // Parameters H0 and H1 are initialized to 20 and 1.
1.278 +
1.279 +
1.280 + ///Runs the second phase of the preflow algorithm.
1.281 +
1.282 + ///The preflow algorithm consists of two phases, this method runs
1.283 + ///the second phase. After calling \ref phase1 and then \ref
1.284 + ///phase2, \ref flow contains a maximum flow, \ref flowValue
1.285 + ///returns the value of a maximum flow, \ref minCut returns a
1.286 + ///minimum cut, while the methods \ref minMinCut and \ref
1.287 + ///maxMinCut return the inclusionwise minimum and maximum cuts of
1.288 + ///minimum value, resp. \pre \ref phase1 must be called before.
1.289 + void phase2()
1.290 + {
1.291 +
1.292 + int k=n-2; //bound on the highest level under n containing a node
1.293 + int b=k; //bound on the highest level under n of an active node
1.294 +
1.295 +
1.296 + VecNode first(n, INVALID);
1.297 + NNMap next(*g, INVALID);
1.298 + level.set(s,0);
1.299 + std::queue<Node> bfs_queue;
1.300 + bfs_queue.push(s);
1.301 +
1.302 + while ( !bfs_queue.empty() ) {
1.303 +
1.304 + Node v=bfs_queue.front();
1.305 + bfs_queue.pop();
1.306 + int l=level[v]+1;
1.307 +
1.308 + for(InEdgeIt e(*g,v); e!=INVALID; ++e) {
1.309 + if ( (*capacity)[e] <= (*flow)[e] ) continue;
1.310 + Node u=g->tail(e);
1.311 + if ( level[u] >= n ) {
1.312 + bfs_queue.push(u);
1.313 + level.set(u, l);
1.314 + if ( excess[u] > 0 ) {
1.315 + next.set(u,first[l]);
1.316 + first[l]=u;
1.317 + }
1.318 + }
1.319 + }
1.320 +
1.321 + for(OutEdgeIt e(*g,v); e!=INVALID; ++e) {
1.322 + if ( 0 >= (*flow)[e] ) continue;
1.323 + Node u=g->head(e);
1.324 + if ( level[u] >= n ) {
1.325 + bfs_queue.push(u);
1.326 + level.set(u, l);
1.327 + if ( excess[u] > 0 ) {
1.328 + next.set(u,first[l]);
1.329 + first[l]=u;
1.330 + }
1.331 + }
1.332 + }
1.333 + }
1.334 + b=n-2;
1.335 +
1.336 + while ( true ) {
1.337 +
1.338 + if ( b == 0 ) break;
1.339 + if ( first[b]==INVALID ) --b;
1.340 + else {
1.341 + Node w=first[b];
1.342 + first[b]=next[w];
1.343 + int newlevel=push(w,next, first);
1.344 +
1.345 + //relabel
1.346 + if ( excess[w] > 0 ) {
1.347 + level.set(w,++newlevel);
1.348 + next.set(w,first[newlevel]);
1.349 + first[newlevel]=w;
1.350 + b=newlevel;
1.351 + }
1.352 + }
1.353 + } // while(true)
1.354 + flow_prop=GEN_FLOW;
1.355 + status=AFTER_PREFLOW_PHASE_2;
1.356 + }
1.357 +
1.358 + /// Returns the value of the maximum flow.
1.359 +
1.360 + /// Returns the value of the maximum flow by returning the excess
1.361 + /// of the target node \c t. This value equals to the value of
1.362 + /// the maximum flow already after running \ref phase1.
1.363 + Num flowValue() const {
1.364 + return excess[t];
1.365 + }
1.366 +
1.367 +
1.368 + ///Returns a minimum value cut.
1.369 +
1.370 + ///Sets \c M to the characteristic vector of a minimum value
1.371 + ///cut. This method can be called both after running \ref
1.372 + ///phase1 and \ref phase2. It is much faster after
1.373 + ///\ref phase1. \pre M should be a bool-valued node-map. \pre
1.374 + ///If \ref minCut() is called after \ref phase2() then M should
1.375 + ///be initialized to false.
1.376 + template<typename _CutMap>
1.377 + void minCut(_CutMap& M) const {
1.378 + switch ( status ) {
1.379 + case AFTER_PREFLOW_PHASE_1:
1.380 + for(NodeIt v(*g); v!=INVALID; ++v) {
1.381 + if (level[v] < n) {
1.382 + M.set(v, false);
1.383 + } else {
1.384 + M.set(v, true);
1.385 + }
1.386 + }
1.387 + break;
1.388 + case AFTER_PREFLOW_PHASE_2:
1.389 + minMinCut(M);
1.390 + break;
1.391 + case AFTER_NOTHING:
1.392 + break;
1.393 + }
1.394 + }
1.395 +
1.396 + ///Returns the inclusionwise minimum of the minimum value cuts.
1.397 +
1.398 + ///Sets \c M to the characteristic vector of the minimum value cut
1.399 + ///which is inclusionwise minimum. It is computed by processing a
1.400 + ///bfs from the source node \c s in the residual graph. \pre M
1.401 + ///should be a node map of bools initialized to false. \pre \ref
1.402 + ///phase2 should already be run.
1.403 + template<typename _CutMap>
1.404 + void minMinCut(_CutMap& M) const {
1.405 +
1.406 + std::queue<Node> queue;
1.407 + M.set(s,true);
1.408 + queue.push(s);
1.409 +
1.410 + while (!queue.empty()) {
1.411 + Node w=queue.front();
1.412 + queue.pop();
1.413 +
1.414 + for(OutEdgeIt e(*g,w) ; e!=INVALID; ++e) {
1.415 + Node v=g->head(e);
1.416 + if (!M[v] && (*flow)[e] < (*capacity)[e] ) {
1.417 + queue.push(v);
1.418 + M.set(v, true);
1.419 + }
1.420 + }
1.421 +
1.422 + for(InEdgeIt e(*g,w) ; e!=INVALID; ++e) {
1.423 + Node v=g->tail(e);
1.424 + if (!M[v] && (*flow)[e] > 0 ) {
1.425 + queue.push(v);
1.426 + M.set(v, true);
1.427 + }
1.428 + }
1.429 + }
1.430 + }
1.431 +
1.432 + ///Returns the inclusionwise maximum of the minimum value cuts.
1.433 +
1.434 + ///Sets \c M to the characteristic vector of the minimum value cut
1.435 + ///which is inclusionwise maximum. It is computed by processing a
1.436 + ///backward bfs from the target node \c t in the residual graph.
1.437 + ///\pre \ref phase2() or run() should already be run.
1.438 + template<typename _CutMap>
1.439 + void maxMinCut(_CutMap& M) const {
1.440 +
1.441 + for(NodeIt v(*g) ; v!=INVALID; ++v) M.set(v, true);
1.442 +
1.443 + std::queue<Node> queue;
1.444 +
1.445 + M.set(t,false);
1.446 + queue.push(t);
1.447 +
1.448 + while (!queue.empty()) {
1.449 + Node w=queue.front();
1.450 + queue.pop();
1.451 +
1.452 + for(InEdgeIt e(*g,w) ; e!=INVALID; ++e) {
1.453 + Node v=g->tail(e);
1.454 + if (M[v] && (*flow)[e] < (*capacity)[e] ) {
1.455 + queue.push(v);
1.456 + M.set(v, false);
1.457 + }
1.458 + }
1.459 +
1.460 + for(OutEdgeIt e(*g,w) ; e!=INVALID; ++e) {
1.461 + Node v=g->head(e);
1.462 + if (M[v] && (*flow)[e] > 0 ) {
1.463 + queue.push(v);
1.464 + M.set(v, false);
1.465 + }
1.466 + }
1.467 + }
1.468 + }
1.469 +
1.470 + ///Sets the source node to \c _s.
1.471 +
1.472 + ///Sets the source node to \c _s.
1.473 + ///
1.474 + void setSource(Node _s) {
1.475 + s=_s;
1.476 + if ( flow_prop != ZERO_FLOW ) flow_prop=NO_FLOW;
1.477 + status=AFTER_NOTHING;
1.478 + }
1.479 +
1.480 + ///Sets the target node to \c _t.
1.481 +
1.482 + ///Sets the target node to \c _t.
1.483 + ///
1.484 + void setTarget(Node _t) {
1.485 + t=_t;
1.486 + if ( flow_prop == GEN_FLOW ) flow_prop=PRE_FLOW;
1.487 + status=AFTER_NOTHING;
1.488 + }
1.489 +
1.490 + /// Sets the edge map of the capacities to _cap.
1.491 +
1.492 + /// Sets the edge map of the capacities to _cap.
1.493 + ///
1.494 + void setCap(const CapMap& _cap) {
1.495 + capacity=&_cap;
1.496 + status=AFTER_NOTHING;
1.497 + }
1.498 +
1.499 + /// Sets the edge map of the flows to _flow.
1.500 +
1.501 + /// Sets the edge map of the flows to _flow.
1.502 + ///
1.503 + void setFlow(FlowMap& _flow) {
1.504 + flow=&_flow;
1.505 + flow_prop=NO_FLOW;
1.506 + status=AFTER_NOTHING;
1.507 + }
1.508 +
1.509 +
1.510 + private:
1.511 +
1.512 + int push(Node w, NNMap& next, VecNode& first) {
1.513 +
1.514 + int lev=level[w];
1.515 + Num exc=excess[w];
1.516 + int newlevel=n; //bound on the next level of w
1.517 +
1.518 + for(OutEdgeIt e(*g,w) ; e!=INVALID; ++e) {
1.519 + if ( (*flow)[e] >= (*capacity)[e] ) continue;
1.520 + Node v=g->head(e);
1.521 +
1.522 + if( lev > level[v] ) { //Push is allowed now
1.523 +
1.524 + if ( excess[v]<=0 && v!=t && v!=s ) {
1.525 + next.set(v,first[level[v]]);
1.526 + first[level[v]]=v;
1.527 + }
1.528 +
1.529 + Num cap=(*capacity)[e];
1.530 + Num flo=(*flow)[e];
1.531 + Num remcap=cap-flo;
1.532 +
1.533 + if ( remcap >= exc ) { //A nonsaturating push.
1.534 +
1.535 + flow->set(e, flo+exc);
1.536 + excess.set(v, excess[v]+exc);
1.537 + exc=0;
1.538 + break;
1.539 +
1.540 + } else { //A saturating push.
1.541 + flow->set(e, cap);
1.542 + excess.set(v, excess[v]+remcap);
1.543 + exc-=remcap;
1.544 + }
1.545 + } else if ( newlevel > level[v] ) newlevel = level[v];
1.546 + } //for out edges wv
1.547 +
1.548 + if ( exc > 0 ) {
1.549 + for(InEdgeIt e(*g,w) ; e!=INVALID; ++e) {
1.550 +
1.551 + if( (*flow)[e] <= 0 ) continue;
1.552 + Node v=g->tail(e);
1.553 +
1.554 + if( lev > level[v] ) { //Push is allowed now
1.555 +
1.556 + if ( excess[v]<=0 && v!=t && v!=s ) {
1.557 + next.set(v,first[level[v]]);
1.558 + first[level[v]]=v;
1.559 + }
1.560 +
1.561 + Num flo=(*flow)[e];
1.562 +
1.563 + if ( flo >= exc ) { //A nonsaturating push.
1.564 +
1.565 + flow->set(e, flo-exc);
1.566 + excess.set(v, excess[v]+exc);
1.567 + exc=0;
1.568 + break;
1.569 + } else { //A saturating push.
1.570 +
1.571 + excess.set(v, excess[v]+flo);
1.572 + exc-=flo;
1.573 + flow->set(e,0);
1.574 + }
1.575 + } else if ( newlevel > level[v] ) newlevel = level[v];
1.576 + } //for in edges vw
1.577 +
1.578 + } // if w still has excess after the out edge for cycle
1.579 +
1.580 + excess.set(w, exc);
1.581 +
1.582 + return newlevel;
1.583 + }
1.584 +
1.585 +
1.586 +
1.587 + void preflowPreproc(VecNode& first, NNMap& next,
1.588 + VecNode& level_list, NNMap& left, NNMap& right)
1.589 + {
1.590 + for(NodeIt v(*g); v!=INVALID; ++v) level.set(v,n);
1.591 + std::queue<Node> bfs_queue;
1.592 +
1.593 + if ( flow_prop == GEN_FLOW || flow_prop == PRE_FLOW ) {
1.594 + //Reverse_bfs from t in the residual graph,
1.595 + //to find the starting level.
1.596 + level.set(t,0);
1.597 + bfs_queue.push(t);
1.598 +
1.599 + while ( !bfs_queue.empty() ) {
1.600 +
1.601 + Node v=bfs_queue.front();
1.602 + bfs_queue.pop();
1.603 + int l=level[v]+1;
1.604 +
1.605 + for(InEdgeIt e(*g,v) ; e!=INVALID; ++e) {
1.606 + if ( (*capacity)[e] <= (*flow)[e] ) continue;
1.607 + Node w=g->tail(e);
1.608 + if ( level[w] == n && w != s ) {
1.609 + bfs_queue.push(w);
1.610 + Node z=level_list[l];
1.611 + if ( z!=INVALID ) left.set(z,w);
1.612 + right.set(w,z);
1.613 + level_list[l]=w;
1.614 + level.set(w, l);
1.615 + }
1.616 + }
1.617 +
1.618 + for(OutEdgeIt e(*g,v) ; e!=INVALID; ++e) {
1.619 + if ( 0 >= (*flow)[e] ) continue;
1.620 + Node w=g->head(e);
1.621 + if ( level[w] == n && w != s ) {
1.622 + bfs_queue.push(w);
1.623 + Node z=level_list[l];
1.624 + if ( z!=INVALID ) left.set(z,w);
1.625 + right.set(w,z);
1.626 + level_list[l]=w;
1.627 + level.set(w, l);
1.628 + }
1.629 + }
1.630 + } //while
1.631 + } //if
1.632 +
1.633 +
1.634 + switch (flow_prop) {
1.635 + case NO_FLOW:
1.636 + for(EdgeIt e(*g); e!=INVALID; ++e) flow->set(e,0);
1.637 + case ZERO_FLOW:
1.638 + for(NodeIt v(*g); v!=INVALID; ++v) excess.set(v,0);
1.639 +
1.640 + //Reverse_bfs from t, to find the starting level.
1.641 + level.set(t,0);
1.642 + bfs_queue.push(t);
1.643 +
1.644 + while ( !bfs_queue.empty() ) {
1.645 +
1.646 + Node v=bfs_queue.front();
1.647 + bfs_queue.pop();
1.648 + int l=level[v]+1;
1.649 +
1.650 + for(InEdgeIt e(*g,v) ; e!=INVALID; ++e) {
1.651 + Node w=g->tail(e);
1.652 + if ( level[w] == n && w != s ) {
1.653 + bfs_queue.push(w);
1.654 + Node z=level_list[l];
1.655 + if ( z!=INVALID ) left.set(z,w);
1.656 + right.set(w,z);
1.657 + level_list[l]=w;
1.658 + level.set(w, l);
1.659 + }
1.660 + }
1.661 + }
1.662 +
1.663 + //the starting flow
1.664 + for(OutEdgeIt e(*g,s) ; e!=INVALID; ++e) {
1.665 + Num c=(*capacity)[e];
1.666 + if ( c <= 0 ) continue;
1.667 + Node w=g->head(e);
1.668 + if ( level[w] < n ) {
1.669 + if ( excess[w] <= 0 && w!=t ) { //putting into the stack
1.670 + next.set(w,first[level[w]]);
1.671 + first[level[w]]=w;
1.672 + }
1.673 + flow->set(e, c);
1.674 + excess.set(w, excess[w]+c);
1.675 + }
1.676 + }
1.677 + break;
1.678 +
1.679 + case GEN_FLOW:
1.680 + for(NodeIt v(*g); v!=INVALID; ++v) excess.set(v,0);
1.681 + {
1.682 + Num exc=0;
1.683 + for(InEdgeIt e(*g,t) ; e!=INVALID; ++e) exc+=(*flow)[e];
1.684 + for(OutEdgeIt e(*g,t) ; e!=INVALID; ++e) exc-=(*flow)[e];
1.685 + excess.set(t,exc);
1.686 + }
1.687 +
1.688 + //the starting flow
1.689 + for(OutEdgeIt e(*g,s); e!=INVALID; ++e) {
1.690 + Num rem=(*capacity)[e]-(*flow)[e];
1.691 + if ( rem <= 0 ) continue;
1.692 + Node w=g->head(e);
1.693 + if ( level[w] < n ) {
1.694 + if ( excess[w] <= 0 && w!=t ) { //putting into the stack
1.695 + next.set(w,first[level[w]]);
1.696 + first[level[w]]=w;
1.697 + }
1.698 + flow->set(e, (*capacity)[e]);
1.699 + excess.set(w, excess[w]+rem);
1.700 + }
1.701 + }
1.702 +
1.703 + for(InEdgeIt e(*g,s); e!=INVALID; ++e) {
1.704 + if ( (*flow)[e] <= 0 ) continue;
1.705 + Node w=g->tail(e);
1.706 + if ( level[w] < n ) {
1.707 + if ( excess[w] <= 0 && w!=t ) {
1.708 + next.set(w,first[level[w]]);
1.709 + first[level[w]]=w;
1.710 + }
1.711 + excess.set(w, excess[w]+(*flow)[e]);
1.712 + flow->set(e, 0);
1.713 + }
1.714 + }
1.715 + break;
1.716 +
1.717 + case PRE_FLOW:
1.718 + //the starting flow
1.719 + for(OutEdgeIt e(*g,s) ; e!=INVALID; ++e) {
1.720 + Num rem=(*capacity)[e]-(*flow)[e];
1.721 + if ( rem <= 0 ) continue;
1.722 + Node w=g->head(e);
1.723 + if ( level[w] < n ) flow->set(e, (*capacity)[e]);
1.724 + }
1.725 +
1.726 + for(InEdgeIt e(*g,s) ; e!=INVALID; ++e) {
1.727 + if ( (*flow)[e] <= 0 ) continue;
1.728 + Node w=g->tail(e);
1.729 + if ( level[w] < n ) flow->set(e, 0);
1.730 + }
1.731 +
1.732 + //computing the excess
1.733 + for(NodeIt w(*g); w!=INVALID; ++w) {
1.734 + Num exc=0;
1.735 + for(InEdgeIt e(*g,w); e!=INVALID; ++e) exc+=(*flow)[e];
1.736 + for(OutEdgeIt e(*g,w); e!=INVALID; ++e) exc-=(*flow)[e];
1.737 + excess.set(w,exc);
1.738 +
1.739 + //putting the active nodes into the stack
1.740 + int lev=level[w];
1.741 + if ( exc > 0 && lev < n && Node(w) != t ) {
1.742 + next.set(w,first[lev]);
1.743 + first[lev]=w;
1.744 + }
1.745 + }
1.746 + break;
1.747 + } //switch
1.748 + } //preflowPreproc
1.749 +
1.750 +
1.751 + void relabel(Node w, int newlevel, VecNode& first, NNMap& next,
1.752 + VecNode& level_list, NNMap& left,
1.753 + NNMap& right, int& b, int& k, bool what_heur )
1.754 + {
1.755 +
1.756 + int lev=level[w];
1.757 +
1.758 + Node right_n=right[w];
1.759 + Node left_n=left[w];
1.760 +
1.761 + //unlacing starts
1.762 + if ( right_n!=INVALID ) {
1.763 + if ( left_n!=INVALID ) {
1.764 + right.set(left_n, right_n);
1.765 + left.set(right_n, left_n);
1.766 + } else {
1.767 + level_list[lev]=right_n;
1.768 + left.set(right_n, INVALID);
1.769 + }
1.770 + } else {
1.771 + if ( left_n!=INVALID ) {
1.772 + right.set(left_n, INVALID);
1.773 + } else {
1.774 + level_list[lev]=INVALID;
1.775 + }
1.776 + }
1.777 + //unlacing ends
1.778 +
1.779 + if ( level_list[lev]==INVALID ) {
1.780 +
1.781 + //gapping starts
1.782 + for (int i=lev; i!=k ; ) {
1.783 + Node v=level_list[++i];
1.784 + while ( v!=INVALID ) {
1.785 + level.set(v,n);
1.786 + v=right[v];
1.787 + }
1.788 + level_list[i]=INVALID;
1.789 + if ( !what_heur ) first[i]=INVALID;
1.790 + }
1.791 +
1.792 + level.set(w,n);
1.793 + b=lev-1;
1.794 + k=b;
1.795 + //gapping ends
1.796 +
1.797 + } else {
1.798 +
1.799 + if ( newlevel == n ) level.set(w,n);
1.800 + else {
1.801 + level.set(w,++newlevel);
1.802 + next.set(w,first[newlevel]);
1.803 + first[newlevel]=w;
1.804 + if ( what_heur ) b=newlevel;
1.805 + if ( k < newlevel ) ++k; //now k=newlevel
1.806 + Node z=level_list[newlevel];
1.807 + if ( z!=INVALID ) left.set(z,w);
1.808 + right.set(w,z);
1.809 + left.set(w,INVALID);
1.810 + level_list[newlevel]=w;
1.811 + }
1.812 + }
1.813 + } //relabel
1.814 +
1.815 + };
1.816 +} //namespace lemon
1.817 +
1.818 +#endif //LEMON_PREFLOW_H
1.819 +
1.820 +
1.821 +
1.822 +