1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/src/work/jacint/preflow.h Sat Feb 21 21:01:22 2004 +0000
1.3 @@ -0,0 +1,532 @@
1.4 +// -*- C++ -*-
1.5 +/*
1.6 +preflow.h
1.7 +by jacint.
1.8 +Heuristics:
1.9 + 2 phase
1.10 + gap
1.11 + list 'level_list' on the nodes on level i implemented by hand
1.12 + stack 'active' on the active nodes on level i implemented by hand
1.13 + runs heuristic 'highest label' for H1*n relabels
1.14 + runs heuristic 'dound decrease' for H0*n relabels, starts with 'highest label'
1.15 +
1.16 +Parameters H0 and H1 are initialized to 20 and 10.
1.17 +
1.18 +The best preflow I could ever write.
1.19 +
1.20 +The constructor runs the algorithm.
1.21 +
1.22 +Members:
1.23 +
1.24 +T maxFlow() : returns the value of a maximum flow
1.25 +
1.26 +T flowOnEdge(EdgeIt e) : for a fixed maximum flow x it returns x(e)
1.27 +
1.28 +FlowMap Flow() : returns the fixed maximum flow x
1.29 +
1.30 +void minMinCut(CutMap& M) : sets M to the characteristic vector of the
1.31 + minimum min cut. M should be a map of bools initialized to false.
1.32 +
1.33 +void maxMinCut(CutMap& M) : sets M to the characteristic vector of the
1.34 + maximum min cut. M should be a map of bools initialized to false.
1.35 +
1.36 +void minCut(CutMap& M) : sets M to the characteristic vector of
1.37 + a min cut. M should be a map of bools initialized to false.
1.38 +
1.39 +*/
1.40 +
1.41 +#ifndef PREFLOW_H
1.42 +#define PREFLOW_H
1.43 +
1.44 +#define H0 20
1.45 +#define H1 1
1.46 +
1.47 +#include <vector>
1.48 +#include <queue>
1.49 +
1.50 +namespace hugo {
1.51 +
1.52 + template <typename Graph, typename T,
1.53 + typename FlowMap=typename Graph::EdgeMap<T>,
1.54 + typename CapMap=typename Graph::EdgeMap<T> >
1.55 + class preflow {
1.56 +
1.57 + typedef typename Graph::NodeIt NodeIt;
1.58 + typedef typename Graph::EdgeIt EdgeIt;
1.59 + typedef typename Graph::EachNodeIt EachNodeIt;
1.60 + typedef typename Graph::OutEdgeIt OutEdgeIt;
1.61 + typedef typename Graph::InEdgeIt InEdgeIt;
1.62 +
1.63 + Graph& G;
1.64 + NodeIt s;
1.65 + NodeIt t;
1.66 + FlowMap flow;
1.67 + CapMap& capacity;
1.68 + T value;
1.69 +
1.70 + public:
1.71 +
1.72 + preflow(Graph& _G, NodeIt _s, NodeIt _t, CapMap& _capacity ) :
1.73 + G(_G), s(_s), t(_t), flow(_G, 0), capacity(_capacity)
1.74 + {
1.75 +
1.76 + bool phase=0; //phase 0 is the 1st phase, phase 1 is the 2nd
1.77 + int n=G.nodeNum();
1.78 + int heur0=(int)(H0*n); //time while running 'bound decrease'
1.79 + int heur1=(int)(H1*n); //time while running 'highest label'
1.80 + int heur=heur1; //starting time interval (#of relabels)
1.81 + bool what_heur=1;
1.82 + /*
1.83 + what_heur is 0 in case 'bound decrease'
1.84 + and 1 in case 'highest label'
1.85 + */
1.86 + bool end=false;
1.87 + /*
1.88 + Needed for 'bound decrease', 'true'
1.89 + means no active nodes are above bound b.
1.90 + */
1.91 + int relabel=0;
1.92 + int k=n-2; //bound on the highest level under n containing a node
1.93 + int b=k; //bound on the highest level under n of an active node
1.94 +
1.95 + typename Graph::NodeMap<int> level(G,n);
1.96 + typename Graph::NodeMap<T> excess(G);
1.97 +
1.98 + std::vector<NodeIt> active(n);
1.99 + typename Graph::NodeMap<NodeIt> next(G);
1.100 + //Stack of the active nodes in level i < n.
1.101 + //We use it in both phases.
1.102 +
1.103 + typename Graph::NodeMap<NodeIt> left(G);
1.104 + typename Graph::NodeMap<NodeIt> right(G);
1.105 + std::vector<NodeIt> level_list(n);
1.106 + /*
1.107 + List of the nodes in level i<n.
1.108 + */
1.109 +
1.110 + /*Reverse_bfs from t, to find the starting level.*/
1.111 + level.set(t,0);
1.112 + std::queue<NodeIt> bfs_queue;
1.113 + bfs_queue.push(t);
1.114 +
1.115 + while (!bfs_queue.empty()) {
1.116 +
1.117 + NodeIt v=bfs_queue.front();
1.118 + bfs_queue.pop();
1.119 + int l=level.get(v)+1;
1.120 +
1.121 + for(InEdgeIt e=G.template first<InEdgeIt>(v); e.valid(); ++e) {
1.122 + NodeIt w=G.tail(e);
1.123 + if ( level.get(w) == n && w != s ) {
1.124 + bfs_queue.push(w);
1.125 + NodeIt first=level_list[l];
1.126 + if ( first != 0 ) left.set(first,w);
1.127 + right.set(w,first);
1.128 + level_list[l]=w;
1.129 + level.set(w, l);
1.130 + }
1.131 + }
1.132 + }
1.133 +
1.134 + level.set(s,n);
1.135 +
1.136 +
1.137 + /* Starting flow. It is everywhere 0 at the moment. */
1.138 + for(OutEdgeIt e=G.template first<OutEdgeIt>(s); e.valid(); ++e)
1.139 + {
1.140 + T c=capacity.get(e);
1.141 + if ( c == 0 ) continue;
1.142 + NodeIt w=G.head(e);
1.143 + if ( level.get(w) < n ) {
1.144 + if ( excess.get(w) == 0 && w!=t ) {
1.145 + next.set(w,active[level.get(w)]);
1.146 + active[level.get(w)]=w;
1.147 + }
1.148 + flow.set(e, c);
1.149 + excess.set(w, excess.get(w)+c);
1.150 + }
1.151 + }
1.152 +
1.153 + /*
1.154 + End of preprocessing
1.155 + */
1.156 +
1.157 +
1.158 +
1.159 + /*
1.160 + Push/relabel on the highest level active nodes.
1.161 + */
1.162 + while ( true ) {
1.163 +
1.164 + if ( b == 0 ) {
1.165 + if ( phase ) break;
1.166 +
1.167 + if ( !what_heur && !end && k > 0 ) {
1.168 + b=k;
1.169 + end=true;
1.170 + } else {
1.171 + phase=1;
1.172 +
1.173 + level.set(s,0);
1.174 + std::queue<NodeIt> bfs_queue;
1.175 + bfs_queue.push(s);
1.176 +
1.177 + while (!bfs_queue.empty()) {
1.178 +
1.179 + NodeIt v=bfs_queue.front();
1.180 + bfs_queue.pop();
1.181 + int l=level.get(v)+1;
1.182 +
1.183 + for(InEdgeIt e=G.template first<InEdgeIt>(v); e.valid(); ++e) {
1.184 + if ( capacity.get(e) == flow.get(e) ) continue;
1.185 + NodeIt u=G.tail(e);
1.186 + if ( level.get(u) >= n ) {
1.187 + bfs_queue.push(u);
1.188 + level.set(u, l);
1.189 + if ( excess.get(u) > 0 ) {
1.190 + next.set(u,active[l]);
1.191 + active[l]=u;
1.192 + }
1.193 + }
1.194 + }
1.195 +
1.196 + for(OutEdgeIt e=G.template first<OutEdgeIt>(v); e.valid(); ++e) {
1.197 + if ( 0 == flow.get(e) ) continue;
1.198 + NodeIt u=G.head(e);
1.199 + if ( level.get(u) >= n ) {
1.200 + bfs_queue.push(u);
1.201 + level.set(u, l);
1.202 + if ( excess.get(u) > 0 ) {
1.203 + next.set(u,active[l]);
1.204 + active[l]=u;
1.205 + }
1.206 + }
1.207 + }
1.208 + }
1.209 + b=n-2;
1.210 + }
1.211 +
1.212 + }
1.213 +
1.214 +
1.215 + if ( active[b] == 0 ) --b;
1.216 + else {
1.217 + end=false;
1.218 +
1.219 + NodeIt w=active[b];
1.220 + active[b]=next.get(w);
1.221 + int lev=level.get(w);
1.222 + T exc=excess.get(w);
1.223 + int newlevel=n; //bound on the next level of w
1.224 +
1.225 + for(OutEdgeIt e=G.template first<OutEdgeIt>(w); e.valid(); ++e) {
1.226 +
1.227 + if ( flow.get(e) == capacity.get(e) ) continue;
1.228 + NodeIt v=G.head(e);
1.229 + //e=wv
1.230 +
1.231 + if( lev > level.get(v) ) {
1.232 + /*Push is allowed now*/
1.233 +
1.234 + if ( excess.get(v)==0 && v!=t && v!=s ) {
1.235 + int lev_v=level.get(v);
1.236 + next.set(v,active[lev_v]);
1.237 + active[lev_v]=v;
1.238 + }
1.239 +
1.240 + T cap=capacity.get(e);
1.241 + T flo=flow.get(e);
1.242 + T remcap=cap-flo;
1.243 +
1.244 + if ( remcap >= exc ) {
1.245 + /*A nonsaturating push.*/
1.246 +
1.247 + flow.set(e, flo+exc);
1.248 + excess.set(v, excess.get(v)+exc);
1.249 + exc=0;
1.250 + break;
1.251 +
1.252 + } else {
1.253 + /*A saturating push.*/
1.254 +
1.255 + flow.set(e, cap);
1.256 + excess.set(v, excess.get(v)+remcap);
1.257 + exc-=remcap;
1.258 + }
1.259 + } else if ( newlevel > level.get(v) ){
1.260 + newlevel = level.get(v);
1.261 + }
1.262 +
1.263 + } //for out edges wv
1.264 +
1.265 +
1.266 + if ( exc > 0 ) {
1.267 + for( InEdgeIt e=G.template first<InEdgeIt>(w); e.valid(); ++e) {
1.268 +
1.269 + if( flow.get(e) == 0 ) continue;
1.270 + NodeIt v=G.tail(e);
1.271 + //e=vw
1.272 +
1.273 + if( lev > level.get(v) ) {
1.274 + /*Push is allowed now*/
1.275 +
1.276 + if ( excess.get(v)==0 && v!=t && v!=s ) {
1.277 + int lev_v=level.get(v);
1.278 + next.set(v,active[lev_v]);
1.279 + active[lev_v]=v;
1.280 + }
1.281 +
1.282 + T flo=flow.get(e);
1.283 +
1.284 + if ( flo >= exc ) {
1.285 + /*A nonsaturating push.*/
1.286 +
1.287 + flow.set(e, flo-exc);
1.288 + excess.set(v, excess.get(v)+exc);
1.289 + exc=0;
1.290 + break;
1.291 + } else {
1.292 + /*A saturating push.*/
1.293 +
1.294 + excess.set(v, excess.get(v)+flo);
1.295 + exc-=flo;
1.296 + flow.set(e,0);
1.297 + }
1.298 + } else if ( newlevel > level.get(v) ) {
1.299 + newlevel = level.get(v);
1.300 + }
1.301 + } //for in edges vw
1.302 +
1.303 + } // if w still has excess after the out edge for cycle
1.304 +
1.305 + excess.set(w, exc);
1.306 +
1.307 + /*
1.308 + Relabel
1.309 + */
1.310 +
1.311 +
1.312 + if ( exc > 0 ) {
1.313 + //now 'lev' is the old level of w
1.314 +
1.315 + if ( phase ) {
1.316 + level.set(w,++newlevel);
1.317 + next.set(w,active[newlevel]);
1.318 + active[newlevel]=w;
1.319 + b=newlevel;
1.320 + } else {
1.321 + //unlacing starts
1.322 + NodeIt right_n=right.get(w);
1.323 + NodeIt left_n=left.get(w);
1.324 +
1.325 + if ( right_n != 0 ) {
1.326 + if ( left_n != 0 ) {
1.327 + right.set(left_n, right_n);
1.328 + left.set(right_n, left_n);
1.329 + } else {
1.330 + level_list[lev]=right_n;
1.331 + left.set(right_n, 0);
1.332 + }
1.333 + } else {
1.334 + if ( left_n != 0 ) {
1.335 + right.set(left_n, 0);
1.336 + } else {
1.337 + level_list[lev]=0;
1.338 +
1.339 + }
1.340 + }
1.341 + //unlacing ends
1.342 +
1.343 + //gapping starts
1.344 + if ( level_list[lev]==0 ) {
1.345 +
1.346 + for (int i=lev; i!=k ; ) {
1.347 + NodeIt v=level_list[++i];
1.348 + while ( v != 0 ) {
1.349 + level.set(v,n);
1.350 + v=right.get(v);
1.351 + }
1.352 + level_list[i]=0;
1.353 + if ( !what_heur ) active[i]=0;
1.354 + }
1.355 +
1.356 + level.set(w,n);
1.357 + b=lev-1;
1.358 + k=b;
1.359 + //gapping ends
1.360 + } else {
1.361 +
1.362 + if ( newlevel == n ) level.set(w,n);
1.363 + else {
1.364 + level.set(w,++newlevel);
1.365 + next.set(w,active[newlevel]);
1.366 + active[newlevel]=w;
1.367 + if ( what_heur ) b=newlevel;
1.368 + if ( k < newlevel ) ++k;
1.369 + NodeIt first=level_list[newlevel];
1.370 + if ( first != 0 ) left.set(first,w);
1.371 + right.set(w,first);
1.372 + left.set(w,0);
1.373 + level_list[newlevel]=w;
1.374 + }
1.375 + }
1.376 +
1.377 +
1.378 + ++relabel;
1.379 + if ( relabel >= heur ) {
1.380 + relabel=0;
1.381 + if ( what_heur ) {
1.382 + what_heur=0;
1.383 + heur=heur0;
1.384 + end=false;
1.385 + } else {
1.386 + what_heur=1;
1.387 + heur=heur1;
1.388 + b=k;
1.389 + }
1.390 + }
1.391 + } //phase 0
1.392 +
1.393 +
1.394 + } // if ( exc > 0 )
1.395 +
1.396 +
1.397 + } // if stack[b] is nonempty
1.398 +
1.399 + } // while(true)
1.400 +
1.401 +
1.402 + value = excess.get(t);
1.403 + /*Max flow value.*/
1.404 +
1.405 + } //void run()
1.406 +
1.407 +
1.408 +
1.409 +
1.410 +
1.411 + /*
1.412 + Returns the maximum value of a flow.
1.413 + */
1.414 +
1.415 + T maxFlow() {
1.416 + return value;
1.417 + }
1.418 +
1.419 +
1.420 +
1.421 + /*
1.422 + For the maximum flow x found by the algorithm,
1.423 + it returns the flow value on edge e, i.e. x(e).
1.424 + */
1.425 +
1.426 + T flowOnEdge(EdgeIt e) {
1.427 + return flow.get(e);
1.428 + }
1.429 +
1.430 +
1.431 +
1.432 + FlowMap Flow() {
1.433 + return flow;
1.434 + }
1.435 +
1.436 +
1.437 +
1.438 + void Flow(FlowMap& _flow ) {
1.439 + for(EachNodeIt v=G.template first<EachNodeIt>() ; v.valid(); ++v)
1.440 + _flow.set(v,flow.get(v));
1.441 + }
1.442 +
1.443 +
1.444 +
1.445 + /*
1.446 + Returns the minimum min cut, by a bfs from s in the residual graph.
1.447 + */
1.448 +
1.449 + template<typename _CutMap>
1.450 + void minMinCut(_CutMap& M) {
1.451 +
1.452 + std::queue<NodeIt> queue;
1.453 +
1.454 + M.set(s,true);
1.455 + queue.push(s);
1.456 +
1.457 + while (!queue.empty()) {
1.458 + NodeIt w=queue.front();
1.459 + queue.pop();
1.460 +
1.461 + for(OutEdgeIt e=G.template first<OutEdgeIt>(w) ; e.valid(); ++e) {
1.462 + NodeIt v=G.head(e);
1.463 + if (!M.get(v) && flow.get(e) < capacity.get(e) ) {
1.464 + queue.push(v);
1.465 + M.set(v, true);
1.466 + }
1.467 + }
1.468 +
1.469 + for(InEdgeIt e=G.template first<InEdgeIt>(w) ; e.valid(); ++e) {
1.470 + NodeIt v=G.tail(e);
1.471 + if (!M.get(v) && flow.get(e) > 0 ) {
1.472 + queue.push(v);
1.473 + M.set(v, true);
1.474 + }
1.475 + }
1.476 + }
1.477 + }
1.478 +
1.479 +
1.480 +
1.481 + /*
1.482 + Returns the maximum min cut, by a reverse bfs
1.483 + from t in the residual graph.
1.484 + */
1.485 +
1.486 + template<typename _CutMap>
1.487 + void maxMinCut(_CutMap& M) {
1.488 +
1.489 + std::queue<NodeIt> queue;
1.490 +
1.491 + M.set(t,true);
1.492 + queue.push(t);
1.493 +
1.494 + while (!queue.empty()) {
1.495 + NodeIt w=queue.front();
1.496 + queue.pop();
1.497 +
1.498 + for(InEdgeIt e=G.template first<InEdgeIt>(w) ; e.valid(); ++e) {
1.499 + NodeIt v=G.tail(e);
1.500 + if (!M.get(v) && flow.get(e) < capacity.get(e) ) {
1.501 + queue.push(v);
1.502 + M.set(v, true);
1.503 + }
1.504 + }
1.505 +
1.506 + for(OutEdgeIt e=G.template first<OutEdgeIt>(w) ; e.valid(); ++e) {
1.507 + NodeIt v=G.head(e);
1.508 + if (!M.get(v) && flow.get(e) > 0 ) {
1.509 + queue.push(v);
1.510 + M.set(v, true);
1.511 + }
1.512 + }
1.513 + }
1.514 +
1.515 + for(EachNodeIt v=G.template first<EachNodeIt>() ; v.valid(); ++v) {
1.516 + M.set(v, !M.get(v));
1.517 + }
1.518 +
1.519 + }
1.520 +
1.521 +
1.522 +
1.523 + template<typename CutMap>
1.524 + void minCut(CutMap& M) {
1.525 + minMinCut(M);
1.526 + }
1.527 +
1.528 +
1.529 + };
1.530 +}//namespace marci
1.531 +#endif
1.532 +
1.533 +
1.534 +
1.535 +