1.1 --- a/src/hugo/preflow.h Wed Sep 29 14:12:26 2004 +0000
1.2 +++ /dev/null Thu Jan 01 00:00:00 1970 +0000
1.3 @@ -1,819 +0,0 @@
1.4 -/* -*- C++ -*-
1.5 - * src/hugo/preflow.h - Part of HUGOlib, 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 HUGO_PREFLOW_H
1.21 -#define HUGO_PREFLOW_H
1.22 -
1.23 -#include <vector>
1.24 -#include <queue>
1.25 -
1.26 -#include <hugo/invalid.h>
1.27 -#include <hugo/maps.h>
1.28 -
1.29 -/// \file
1.30 -/// \ingroup flowalgs
1.31 -/// Implementation of the preflow algorithm.
1.32 -
1.33 -namespace hugo {
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 hugo::Preflow::phase1() "phase1()"
1.51 - ///or \ref hugo::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 hugo
1.817 -
1.818 -#endif //HUGO_PREFLOW_H
1.819 -
1.820 -
1.821 -
1.822 -