lemon-0.x: src/work/jacint/preflow.h@3a5ebcd91d37 (annotated)

jacint@109	1	// -- C++ --
jacint@109	2	/*
jacint@109	3	preflow.h
jacint@109	4	by jacint.
jacint@109	5	Heuristics:
jacint@109	6	2 phase
jacint@109	7	gap
jacint@109	8	list 'level_list' on the nodes on level i implemented by hand
jacint@109	9	stack 'active' on the active nodes on level i implemented by hand
jacint@109	10	runs heuristic 'highest label' for H1*n relabels
jacint@109	11	runs heuristic 'dound decrease' for H0*n relabels, starts with 'highest label'
jacint@109	12
jacint@109	13	Parameters H0 and H1 are initialized to 20 and 10.
jacint@109	14
jacint@109	15	The best preflow I could ever write.
jacint@109	16
jacint@109	17	The constructor runs the algorithm.
jacint@109	18
jacint@109	19	Members:
jacint@109	20
jacint@109	21	T maxFlow() : returns the value of a maximum flow
jacint@109	22
jacint@109	23	T flowOnEdge(EdgeIt e) : for a fixed maximum flow x it returns x(e)
jacint@109	24
jacint@109	25	FlowMap Flow() : returns the fixed maximum flow x
jacint@109	26
jacint@109	27	void minMinCut(CutMap& M) : sets M to the characteristic vector of the
jacint@109	28	minimum min cut. M should be a map of bools initialized to false.
jacint@109	29
jacint@109	30	void maxMinCut(CutMap& M) : sets M to the characteristic vector of the
jacint@109	31	maximum min cut. M should be a map of bools initialized to false.
jacint@109	32
jacint@109	33	void minCut(CutMap& M) : sets M to the characteristic vector of
jacint@109	34	a min cut. M should be a map of bools initialized to false.
jacint@109	35
jacint@109	36	*/
jacint@109	37
jacint@109	38	#ifndef PREFLOW_H
jacint@109	39	#define PREFLOW_H
jacint@109	40
jacint@109	41	#define H0 20
jacint@109	42	#define H1 1
jacint@109	43
jacint@109	44	#include <vector>
jacint@109	45	#include <queue>
jacint@109	46
jacint@109	47	namespace hugo {
jacint@109	48
jacint@109	49	template <typename Graph, typename T,
jacint@109	50	typename FlowMap=typename Graph::EdgeMap<T>,
jacint@109	51	typename CapMap=typename Graph::EdgeMap<T> >
jacint@109	52	class preflow {
jacint@109	53
jacint@109	54	typedef typename Graph::NodeIt NodeIt;
jacint@109	55	typedef typename Graph::EdgeIt EdgeIt;
jacint@109	56	typedef typename Graph::EachNodeIt EachNodeIt;
jacint@109	57	typedef typename Graph::OutEdgeIt OutEdgeIt;
jacint@109	58	typedef typename Graph::InEdgeIt InEdgeIt;
jacint@109	59
jacint@109	60	Graph& G;
jacint@109	61	NodeIt s;
jacint@109	62	NodeIt t;
jacint@109	63	FlowMap flow;
jacint@109	64	CapMap& capacity;
jacint@109	65	T value;
jacint@109	66
jacint@109	67	public:
jacint@109	68
jacint@109	69	preflow(Graph& _G, NodeIt _s, NodeIt _t, CapMap& _capacity ) :
jacint@109	70	G(_G), s(_s), t(_t), flow(_G, 0), capacity(_capacity)
jacint@109	71	{
jacint@109	72
jacint@109	73	bool phase=0; //phase 0 is the 1st phase, phase 1 is the 2nd
jacint@109	74	int n=G.nodeNum();
jacint@109	75	int heur0=(int)(H0*n); //time while running 'bound decrease'
jacint@109	76	int heur1=(int)(H1*n); //time while running 'highest label'
jacint@109	77	int heur=heur1; //starting time interval (#of relabels)
jacint@109	78	bool what_heur=1;
jacint@109	79	/*
jacint@109	80	what_heur is 0 in case 'bound decrease'
jacint@109	81	and 1 in case 'highest label'
jacint@109	82	*/
jacint@109	83	bool end=false;
jacint@109	84	/*
jacint@109	85	Needed for 'bound decrease', 'true'
jacint@109	86	means no active nodes are above bound b.
jacint@109	87	*/
jacint@109	88	int relabel=0;
jacint@109	89	int k=n-2; //bound on the highest level under n containing a node
jacint@109	90	int b=k; //bound on the highest level under n of an active node
jacint@109	91
jacint@109	92	typename Graph::NodeMap<int> level(G,n);
jacint@109	93	typename Graph::NodeMap<T> excess(G);
jacint@109	94
jacint@109	95	std::vector<NodeIt> active(n);
jacint@109	96	typename Graph::NodeMap<NodeIt> next(G);
jacint@109	97	//Stack of the active nodes in level i < n.
jacint@109	98	//We use it in both phases.
jacint@109	99
jacint@109	100	typename Graph::NodeMap<NodeIt> left(G);
jacint@109	101	typename Graph::NodeMap<NodeIt> right(G);
jacint@109	102	std::vector<NodeIt> level_list(n);
jacint@109	103	/*
jacint@109	104	List of the nodes in level i<n.
jacint@109	105	*/
jacint@109	106
jacint@109	107	/Reverse_bfs from t, to find the starting level./
jacint@109	108	level.set(t,0);
jacint@109	109	std::queue<NodeIt> bfs_queue;
jacint@109	110	bfs_queue.push(t);
jacint@109	111
jacint@109	112	while (!bfs_queue.empty()) {
jacint@109	113
jacint@109	114	NodeIt v=bfs_queue.front();
jacint@109	115	bfs_queue.pop();
jacint@109	116	int l=level.get(v)+1;
jacint@109	117
jacint@109	118	for(InEdgeIt e=G.template first<InEdgeIt>(v); e.valid(); ++e) {
jacint@109	119	NodeIt w=G.tail(e);
jacint@109	120	if ( level.get(w) == n && w != s ) {
jacint@109	121	bfs_queue.push(w);
jacint@109	122	NodeIt first=level_list[l];
jacint@109	123	if ( first != 0 ) left.set(first,w);
jacint@109	124	right.set(w,first);
jacint@109	125	level_list[l]=w;
jacint@109	126	level.set(w, l);
jacint@109	127	}
jacint@109	128	}
jacint@109	129	}
jacint@109	130
jacint@109	131	level.set(s,n);
jacint@109	132
jacint@109	133
jacint@109	134	/* Starting flow. It is everywhere 0 at the moment. */
jacint@109	135	for(OutEdgeIt e=G.template first<OutEdgeIt>(s); e.valid(); ++e)
jacint@109	136	{
jacint@109	137	T c=capacity.get(e);
jacint@109	138	if ( c == 0 ) continue;
jacint@109	139	NodeIt w=G.head(e);
jacint@109	140	if ( level.get(w) < n ) {
jacint@109	141	if ( excess.get(w) == 0 && w!=t ) {
jacint@109	142	next.set(w,active[level.get(w)]);
jacint@109	143	active[level.get(w)]=w;
jacint@109	144	}
jacint@109	145	flow.set(e, c);
jacint@109	146	excess.set(w, excess.get(w)+c);
jacint@109	147	}
jacint@109	148	}
jacint@109	149
jacint@109	150	/*
jacint@109	151	End of preprocessing
jacint@109	152	*/
jacint@109	153
jacint@109	154
jacint@109	155
jacint@109	156	/*
jacint@109	157	Push/relabel on the highest level active nodes.
jacint@109	158	*/
jacint@109	159	while ( true ) {
jacint@109	160
jacint@109	161	if ( b == 0 ) {
jacint@109	162	if ( phase ) break;
jacint@109	163
jacint@109	164	if ( !what_heur && !end && k > 0 ) {
jacint@109	165	b=k;
jacint@109	166	end=true;
jacint@109	167	} else {
jacint@109	168	phase=1;
jacint@109	169
jacint@109	170	level.set(s,0);
jacint@109	171	std::queue<NodeIt> bfs_queue;
jacint@109	172	bfs_queue.push(s);
jacint@109	173
jacint@109	174	while (!bfs_queue.empty()) {
jacint@109	175
jacint@109	176	NodeIt v=bfs_queue.front();
jacint@109	177	bfs_queue.pop();
jacint@109	178	int l=level.get(v)+1;
jacint@109	179
jacint@109	180	for(InEdgeIt e=G.template first<InEdgeIt>(v); e.valid(); ++e) {
jacint@109	181	if ( capacity.get(e) == flow.get(e) ) continue;
jacint@109	182	NodeIt u=G.tail(e);
jacint@109	183	if ( level.get(u) >= n ) {
jacint@109	184	bfs_queue.push(u);
jacint@109	185	level.set(u, l);
jacint@109	186	if ( excess.get(u) > 0 ) {
jacint@109	187	next.set(u,active[l]);
jacint@109	188	active[l]=u;
jacint@109	189	}
jacint@109	190	}
jacint@109	191	}
jacint@109	192
jacint@109	193	for(OutEdgeIt e=G.template first<OutEdgeIt>(v); e.valid(); ++e) {
jacint@109	194	if ( 0 == flow.get(e) ) continue;
jacint@109	195	NodeIt u=G.head(e);
jacint@109	196	if ( level.get(u) >= n ) {
jacint@109	197	bfs_queue.push(u);
jacint@109	198	level.set(u, l);
jacint@109	199	if ( excess.get(u) > 0 ) {
jacint@109	200	next.set(u,active[l]);
jacint@109	201	active[l]=u;
jacint@109	202	}
jacint@109	203	}
jacint@109	204	}
jacint@109	205	}
jacint@109	206	b=n-2;
jacint@109	207	}
jacint@109	208
jacint@109	209	}
jacint@109	210
jacint@109	211
jacint@109	212	if ( active[b] == 0 ) --b;
jacint@109	213	else {
jacint@109	214	end=false;
jacint@109	215
jacint@109	216	NodeIt w=active[b];
jacint@109	217	active[b]=next.get(w);
jacint@109	218	int lev=level.get(w);
jacint@109	219	T exc=excess.get(w);
jacint@109	220	int newlevel=n; //bound on the next level of w
jacint@109	221
jacint@109	222	for(OutEdgeIt e=G.template first<OutEdgeIt>(w); e.valid(); ++e) {
jacint@109	223
jacint@109	224	if ( flow.get(e) == capacity.get(e) ) continue;
jacint@109	225	NodeIt v=G.head(e);
jacint@109	226	//e=wv
jacint@109	227
jacint@109	228	if( lev > level.get(v) ) {
jacint@109	229	/Push is allowed now/
jacint@109	230
jacint@109	231	if ( excess.get(v)==0 && v!=t && v!=s ) {
jacint@109	232	int lev_v=level.get(v);
jacint@109	233	next.set(v,active[lev_v]);
jacint@109	234	active[lev_v]=v;
jacint@109	235	}
jacint@109	236
jacint@109	237	T cap=capacity.get(e);
jacint@109	238	T flo=flow.get(e);
jacint@109	239	T remcap=cap-flo;
jacint@109	240
jacint@109	241	if ( remcap >= exc ) {
jacint@109	242	/A nonsaturating push./
jacint@109	243
jacint@109	244	flow.set(e, flo+exc);
jacint@109	245	excess.set(v, excess.get(v)+exc);
jacint@109	246	exc=0;
jacint@109	247	break;
jacint@109	248
jacint@109	249	} else {
jacint@109	250	/A saturating push./
jacint@109	251
jacint@109	252	flow.set(e, cap);
jacint@109	253	excess.set(v, excess.get(v)+remcap);
jacint@109	254	exc-=remcap;
jacint@109	255	}
jacint@109	256	} else if ( newlevel > level.get(v) ){
jacint@109	257	newlevel = level.get(v);
jacint@109	258	}
jacint@109	259
jacint@109	260	} //for out edges wv
jacint@109	261
jacint@109	262
jacint@109	263	if ( exc > 0 ) {
jacint@109	264	for( InEdgeIt e=G.template first<InEdgeIt>(w); e.valid(); ++e) {
jacint@109	265
jacint@109	266	if( flow.get(e) == 0 ) continue;
jacint@109	267	NodeIt v=G.tail(e);
jacint@109	268	//e=vw
jacint@109	269
jacint@109	270	if( lev > level.get(v) ) {
jacint@109	271	/Push is allowed now/
jacint@109	272
jacint@109	273	if ( excess.get(v)==0 && v!=t && v!=s ) {
jacint@109	274	int lev_v=level.get(v);
jacint@109	275	next.set(v,active[lev_v]);
jacint@109	276	active[lev_v]=v;
jacint@109	277	}
jacint@109	278
jacint@109	279	T flo=flow.get(e);
jacint@109	280
jacint@109	281	if ( flo >= exc ) {
jacint@109	282	/A nonsaturating push./
jacint@109	283
jacint@109	284	flow.set(e, flo-exc);
jacint@109	285	excess.set(v, excess.get(v)+exc);
jacint@109	286	exc=0;
jacint@109	287	break;
jacint@109	288	} else {
jacint@109	289	/A saturating push./
jacint@109	290
jacint@109	291	excess.set(v, excess.get(v)+flo);
jacint@109	292	exc-=flo;
jacint@109	293	flow.set(e,0);
jacint@109	294	}
jacint@109	295	} else if ( newlevel > level.get(v) ) {
jacint@109	296	newlevel = level.get(v);
jacint@109	297	}
jacint@109	298	} //for in edges vw
jacint@109	299
jacint@109	300	} // if w still has excess after the out edge for cycle
jacint@109	301
jacint@109	302	excess.set(w, exc);
jacint@109	303
jacint@109	304	/*
jacint@109	305	Relabel
jacint@109	306	*/
jacint@109	307
jacint@109	308
jacint@109	309	if ( exc > 0 ) {
jacint@109	310	//now 'lev' is the old level of w
jacint@109	311
jacint@109	312	if ( phase ) {
jacint@109	313	level.set(w,++newlevel);
jacint@109	314	next.set(w,active[newlevel]);
jacint@109	315	active[newlevel]=w;
jacint@109	316	b=newlevel;
jacint@109	317	} else {
jacint@109	318	//unlacing starts
jacint@109	319	NodeIt right_n=right.get(w);
jacint@109	320	NodeIt left_n=left.get(w);
jacint@109	321
jacint@109	322	if ( right_n != 0 ) {
jacint@109	323	if ( left_n != 0 ) {
jacint@109	324	right.set(left_n, right_n);
jacint@109	325	left.set(right_n, left_n);
jacint@109	326	} else {
jacint@109	327	level_list[lev]=right_n;
jacint@109	328	left.set(right_n, 0);
jacint@109	329	}
jacint@109	330	} else {
jacint@109	331	if ( left_n != 0 ) {
jacint@109	332	right.set(left_n, 0);
jacint@109	333	} else {
jacint@109	334	level_list[lev]=0;
jacint@109	335
jacint@109	336	}
jacint@109	337	}
jacint@109	338	//unlacing ends
jacint@109	339
jacint@109	340	//gapping starts
jacint@109	341	if ( level_list[lev]==0 ) {
jacint@109	342
jacint@109	343	for (int i=lev; i!=k ; ) {
jacint@109	344	NodeIt v=level_list[++i];
jacint@109	345	while ( v != 0 ) {
jacint@109	346	level.set(v,n);
jacint@109	347	v=right.get(v);
jacint@109	348	}
jacint@109	349	level_list[i]=0;
jacint@109	350	if ( !what_heur ) active[i]=0;
jacint@109	351	}
jacint@109	352
jacint@109	353	level.set(w,n);
jacint@109	354	b=lev-1;
jacint@109	355	k=b;
jacint@109	356	//gapping ends
jacint@109	357	} else {
jacint@109	358
jacint@109	359	if ( newlevel == n ) level.set(w,n);
jacint@109	360	else {
jacint@109	361	level.set(w,++newlevel);
jacint@109	362	next.set(w,active[newlevel]);
jacint@109	363	active[newlevel]=w;
jacint@109	364	if ( what_heur ) b=newlevel;
jacint@109	365	if ( k < newlevel ) ++k;
jacint@109	366	NodeIt first=level_list[newlevel];
jacint@109	367	if ( first != 0 ) left.set(first,w);
jacint@109	368	right.set(w,first);
jacint@109	369	left.set(w,0);
jacint@109	370	level_list[newlevel]=w;
jacint@109	371	}
jacint@109	372	}
jacint@109	373
jacint@109	374
jacint@109	375	++relabel;
jacint@109	376	if ( relabel >= heur ) {
jacint@109	377	relabel=0;
jacint@109	378	if ( what_heur ) {
jacint@109	379	what_heur=0;
jacint@109	380	heur=heur0;
jacint@109	381	end=false;
jacint@109	382	} else {
jacint@109	383	what_heur=1;
jacint@109	384	heur=heur1;
jacint@109	385	b=k;
jacint@109	386	}
jacint@109	387	}
jacint@109	388	} //phase 0
jacint@109	389
jacint@109	390
jacint@109	391	} // if ( exc > 0 )
jacint@109	392
jacint@109	393
jacint@109	394	} // if stack[b] is nonempty
jacint@109	395
jacint@109	396	} // while(true)
jacint@109	397
jacint@109	398
jacint@109	399	value = excess.get(t);
jacint@109	400	/Max flow value./
jacint@109	401
jacint@109	402	} //void run()
jacint@109	403
jacint@109	404
jacint@109	405
jacint@109	406
jacint@109	407
jacint@109	408	/*
jacint@109	409	Returns the maximum value of a flow.
jacint@109	410	*/
jacint@109	411
jacint@109	412	T maxFlow() {
jacint@109	413	return value;
jacint@109	414	}
jacint@109	415
jacint@109	416
jacint@109	417
jacint@109	418	/*
jacint@109	419	For the maximum flow x found by the algorithm,
jacint@109	420	it returns the flow value on edge e, i.e. x(e).
jacint@109	421	*/
jacint@109	422
jacint@109	423	T flowOnEdge(EdgeIt e) {
jacint@109	424	return flow.get(e);
jacint@109	425	}
jacint@109	426
jacint@109	427
jacint@109	428
jacint@109	429	FlowMap Flow() {
jacint@109	430	return flow;
jacint@109	431	}
jacint@109	432
jacint@109	433
jacint@109	434
jacint@109	435	void Flow(FlowMap& _flow ) {
jacint@109	436	for(EachNodeIt v=G.template first<EachNodeIt>() ; v.valid(); ++v)
jacint@109	437	_flow.set(v,flow.get(v));
jacint@109	438	}
jacint@109	439
jacint@109	440
jacint@109	441
jacint@109	442	/*
jacint@109	443	Returns the minimum min cut, by a bfs from s in the residual graph.
jacint@109	444	*/
jacint@109	445
jacint@109	446	template<typename _CutMap>
jacint@109	447	void minMinCut(_CutMap& M) {
jacint@109	448
jacint@109	449	std::queue<NodeIt> queue;
jacint@109	450
jacint@109	451	M.set(s,true);
jacint@109	452	queue.push(s);
jacint@109	453
jacint@109	454	while (!queue.empty()) {
jacint@109	455	NodeIt w=queue.front();
jacint@109	456	queue.pop();
jacint@109	457
jacint@109	458	for(OutEdgeIt e=G.template first<OutEdgeIt>(w) ; e.valid(); ++e) {
jacint@109	459	NodeIt v=G.head(e);
jacint@109	460	if (!M.get(v) && flow.get(e) < capacity.get(e) ) {
jacint@109	461	queue.push(v);
jacint@109	462	M.set(v, true);
jacint@109	463	}
jacint@109	464	}
jacint@109	465
jacint@109	466	for(InEdgeIt e=G.template first<InEdgeIt>(w) ; e.valid(); ++e) {
jacint@109	467	NodeIt v=G.tail(e);
jacint@109	468	if (!M.get(v) && flow.get(e) > 0 ) {
jacint@109	469	queue.push(v);
jacint@109	470	M.set(v, true);
jacint@109	471	}
jacint@109	472	}
jacint@109	473	}
jacint@109	474	}
jacint@109	475
jacint@109	476
jacint@109	477
jacint@109	478	/*
jacint@109	479	Returns the maximum min cut, by a reverse bfs
jacint@109	480	from t in the residual graph.
jacint@109	481	*/
jacint@109	482
jacint@109	483	template<typename _CutMap>
jacint@109	484	void maxMinCut(_CutMap& M) {
jacint@109	485
jacint@109	486	std::queue<NodeIt> queue;
jacint@109	487
jacint@109	488	M.set(t,true);
jacint@109	489	queue.push(t);
jacint@109	490
jacint@109	491	while (!queue.empty()) {
jacint@109	492	NodeIt w=queue.front();
jacint@109	493	queue.pop();
jacint@109	494
jacint@109	495	for(InEdgeIt e=G.template first<InEdgeIt>(w) ; e.valid(); ++e) {
jacint@109	496	NodeIt v=G.tail(e);
jacint@109	497	if (!M.get(v) && flow.get(e) < capacity.get(e) ) {
jacint@109	498	queue.push(v);
jacint@109	499	M.set(v, true);
jacint@109	500	}
jacint@109	501	}
jacint@109	502
jacint@109	503	for(OutEdgeIt e=G.template first<OutEdgeIt>(w) ; e.valid(); ++e) {
jacint@109	504	NodeIt v=G.head(e);
jacint@109	505	if (!M.get(v) && flow.get(e) > 0 ) {
jacint@109	506	queue.push(v);
jacint@109	507	M.set(v, true);
jacint@109	508	}
jacint@109	509	}
jacint@109	510	}
jacint@109	511
jacint@109	512	for(EachNodeIt v=G.template first<EachNodeIt>() ; v.valid(); ++v) {
jacint@109	513	M.set(v, !M.get(v));
jacint@109	514	}
jacint@109	515
jacint@109	516	}
jacint@109	517
jacint@109	518
jacint@109	519
jacint@109	520	template<typename CutMap>
jacint@109	521	void minCut(CutMap& M) {
jacint@109	522	minMinCut(M);
jacint@109	523	}
jacint@109	524
jacint@109	525
jacint@109	526	};
jacint@109	527	}//namespace marci
jacint@109	528	#endif
jacint@109	529
jacint@109	530
jacint@109	531
jacint@109	532

author	jacint
	Sat, 21 Feb 2004 22:15:11 +0000
changeset 111	3a5ebcd91d37
child 113	cf7b01232d86
permissions	-rw-r--r--