lemon-0.x: src/work/jacint/preflow_hl0.h@3a5ebcd91d37 (annotated)

jacint@109	1	// -- C++ --
jacint@109	2	/*
jacint@109	3	preflow_hl0.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	bound decrease
jacint@109	11
jacint@109	12	The bound decrease heuristic behaves unexpectedly well.
jacint@109	13
jacint@109	14	The constructor runs the algorithm.
jacint@109	15
jacint@109	16	Members:
jacint@109	17
jacint@109	18	T maxFlow() : returns the value of a maximum flow
jacint@109	19
jacint@109	20	T flowOnEdge(EdgeIt e) : for a fixed maximum flow x it returns x(e)
jacint@109	21
jacint@109	22	FlowMap Flow() : returns the fixed maximum flow x
jacint@109	23
jacint@109	24	void minMinCut(CutMap& M) : sets M to the characteristic vector of the
jacint@109	25	minimum min cut. M should be a map of bools initialized to false.
jacint@109	26
jacint@109	27	void maxMinCut(CutMap& M) : sets M to the characteristic vector of the
jacint@109	28	maximum min cut. M should be a map of bools initialized to false.
jacint@109	29
jacint@109	30
jacint@109	31	void minCut(CutMap& M) : sets M to the characteristic vector of
jacint@109	32	a min cut. M should be a map of bools initialized to false.
jacint@109	33
jacint@109	34	*/
jacint@109	35
jacint@109	36	#ifndef PREFLOW_HL0_H
jacint@109	37	#define PREFLOW_HL0_H
jacint@109	38
jacint@109	39	#include <vector>
jacint@109	40	#include <queue>
jacint@109	41
jacint@109	42	#include <time_measure.h> //for test
jacint@109	43
jacint@109	44	namespace hugo {
jacint@109	45
jacint@109	46	template <typename Graph, typename T,
jacint@109	47	typename FlowMap=typename Graph::EdgeMap<T>,
jacint@109	48	typename CapMap=typename Graph::EdgeMap<T> >
jacint@109	49	class preflow_hl0 {
jacint@109	50
jacint@109	51	typedef typename Graph::NodeIt NodeIt;
jacint@109	52	typedef typename Graph::EdgeIt EdgeIt;
jacint@109	53	typedef typename Graph::EachNodeIt EachNodeIt;
jacint@109	54	typedef typename Graph::OutEdgeIt OutEdgeIt;
jacint@109	55	typedef typename Graph::InEdgeIt InEdgeIt;
jacint@109	56
jacint@109	57	Graph& G;
jacint@109	58	NodeIt s;
jacint@109	59	NodeIt t;
jacint@109	60	FlowMap flow;
jacint@109	61	CapMap& capacity;
jacint@109	62	T value;
jacint@109	63
jacint@109	64	public:
jacint@109	65	double time;
jacint@109	66
jacint@109	67	preflow_hl0(Graph& _G, NodeIt _s, NodeIt _t, CapMap& _capacity ) :
jacint@109	68	G(_G), s(_s), t(_t), flow(_G, 0), capacity(_capacity) {
jacint@109	69
jacint@109	70	bool phase=0; //phase 0 is the 1st phase, phase 1 is the 2nd
jacint@109	71	int n=G.nodeNum();
jacint@109	72	bool end=false;
jacint@109	73	/*
jacint@109	74	'true' means no active nodes are above bound b.
jacint@109	75	*/
jacint@109	76	int k=n-2; //bound on the highest level under n containing a node
jacint@109	77	int b=k; //bound on the highest level under n of an active node
jacint@109	78	/*
jacint@109	79	b is a bound on the highest level of the stack.
jacint@109	80	k is a bound on the highest nonempty level i < n.
jacint@109	81	*/
jacint@109	82
jacint@109	83	typename Graph::NodeMap<int> level(G,n);
jacint@109	84	typename Graph::NodeMap<T> excess(G);
jacint@109	85
jacint@109	86	std::vector<NodeIt> active(n);
jacint@109	87	typename Graph::NodeMap<NodeIt> next(G);
jacint@109	88	//Stack of the active nodes in level i < n.
jacint@109	89	//We use it in both phases.
jacint@109	90
jacint@109	91	typename Graph::NodeMap<NodeIt> left(G);
jacint@109	92	typename Graph::NodeMap<NodeIt> right(G);
jacint@109	93	std::vector<NodeIt> level_list(n);
jacint@109	94	/*
jacint@109	95	List of the nodes in level i<n.
jacint@109	96	*/
jacint@109	97
jacint@109	98	/Reverse_bfs from t, to find the starting level./
jacint@109	99	level.set(t,0);
jacint@109	100	std::queue<NodeIt> bfs_queue;
jacint@109	101	bfs_queue.push(t);
jacint@109	102
jacint@109	103	while (!bfs_queue.empty()) {
jacint@109	104
jacint@109	105	NodeIt v=bfs_queue.front();
jacint@109	106	bfs_queue.pop();
jacint@109	107	int l=level.get(v)+1;
jacint@109	108
jacint@109	109	for(InEdgeIt e=G.template first<InEdgeIt>(v); e.valid(); ++e) {
jacint@109	110	NodeIt w=G.tail(e);
jacint@109	111	if ( level.get(w) == n && w != s ) {
jacint@109	112	bfs_queue.push(w);
jacint@109	113	NodeIt first=level_list[l];
jacint@109	114	if ( first != 0 ) left.set(first,w);
jacint@109	115	right.set(w,first);
jacint@109	116	level_list[l]=w;
jacint@109	117	level.set(w, l);
jacint@109	118	}
jacint@109	119	}
jacint@109	120	}
jacint@109	121
jacint@109	122	level.set(s,n);
jacint@109	123
jacint@109	124
jacint@109	125	/* Starting flow. It is everywhere 0 at the moment. */
jacint@109	126	for(OutEdgeIt e=G.template first<OutEdgeIt>(s); e.valid(); ++e)
jacint@109	127	{
jacint@109	128	T c=capacity.get(e);
jacint@109	129	if ( c == 0 ) continue;
jacint@109	130	NodeIt w=G.head(e);
jacint@109	131	if ( level.get(w) < n ) {
jacint@109	132	if ( excess.get(w) == 0 && w!=t ) {
jacint@109	133	next.set(w,active[level.get(w)]);
jacint@109	134	active[level.get(w)]=w;
jacint@109	135	}
jacint@109	136	flow.set(e, c);
jacint@109	137	excess.set(w, excess.get(w)+c);
jacint@109	138	}
jacint@109	139	}
jacint@109	140
jacint@109	141	/*
jacint@109	142	End of preprocessing
jacint@109	143	*/
jacint@109	144
jacint@109	145
jacint@109	146
jacint@109	147	/*
jacint@109	148	Push/relabel on the highest level active nodes.
jacint@109	149	*/
jacint@109	150	while ( true ) {
jacint@109	151
jacint@109	152	if ( b == 0 ) {
jacint@109	153	if ( phase ) break;
jacint@109	154
jacint@109	155	if ( !end && k > 0 ) {
jacint@109	156	b=k;
jacint@109	157	end=true;
jacint@109	158	} else {
jacint@109	159	phase=1;
jacint@109	160	time=currTime();
jacint@109	161	level.set(s,0);
jacint@109	162	std::queue<NodeIt> bfs_queue;
jacint@109	163	bfs_queue.push(s);
jacint@109	164
jacint@109	165	while (!bfs_queue.empty()) {
jacint@109	166
jacint@109	167	NodeIt v=bfs_queue.front();
jacint@109	168	bfs_queue.pop();
jacint@109	169	int l=level.get(v)+1;
jacint@109	170
jacint@109	171	for(InEdgeIt e=G.template first<InEdgeIt>(v); e.valid(); ++e) {
jacint@109	172	if ( capacity.get(e) == flow.get(e) ) continue;
jacint@109	173	NodeIt u=G.tail(e);
jacint@109	174	if ( level.get(u) >= n ) {
jacint@109	175	bfs_queue.push(u);
jacint@109	176	level.set(u, l);
jacint@109	177	if ( excess.get(u) > 0 ) {
jacint@109	178	next.set(u,active[l]);
jacint@109	179	active[l]=u;
jacint@109	180	}
jacint@109	181	}
jacint@109	182	}
jacint@109	183
jacint@109	184	for(OutEdgeIt e=G.template first<OutEdgeIt>(v); e.valid(); ++e) {
jacint@109	185	if ( 0 == flow.get(e) ) continue;
jacint@109	186	NodeIt u=G.head(e);
jacint@109	187	if ( level.get(u) >= n ) {
jacint@109	188	bfs_queue.push(u);
jacint@109	189	level.set(u, l);
jacint@109	190	if ( excess.get(u) > 0 ) {
jacint@109	191	next.set(u,active[l]);
jacint@109	192	active[l]=u;
jacint@109	193	}
jacint@109	194	}
jacint@109	195	}
jacint@109	196	}
jacint@109	197	b=n-2;
jacint@109	198	}
jacint@109	199
jacint@109	200	}
jacint@109	201
jacint@109	202
jacint@109	203	if ( active[b] == 0 ) --b;
jacint@109	204	else {
jacint@109	205	end=false;
jacint@109	206
jacint@109	207	NodeIt w=active[b];
jacint@109	208	active[b]=next.get(w);
jacint@109	209	int lev=level.get(w);
jacint@109	210	T exc=excess.get(w);
jacint@109	211	int newlevel=n; //bound on the next level of w
jacint@109	212
jacint@109	213	for(OutEdgeIt e=G.template first<OutEdgeIt>(w); e.valid(); ++e) {
jacint@109	214
jacint@109	215	if ( flow.get(e) == capacity.get(e) ) continue;
jacint@109	216	NodeIt v=G.head(e);
jacint@109	217	//e=wv
jacint@109	218
jacint@109	219	if( lev > level.get(v) ) {
jacint@109	220	/Push is allowed now/
jacint@109	221
jacint@109	222	if ( excess.get(v)==0 && v!=t && v!=s ) {
jacint@109	223	int lev_v=level.get(v);
jacint@109	224	next.set(v,active[lev_v]);
jacint@109	225	active[lev_v]=v;
jacint@109	226	}
jacint@109	227
jacint@109	228	T cap=capacity.get(e);
jacint@109	229	T flo=flow.get(e);
jacint@109	230	T remcap=cap-flo;
jacint@109	231
jacint@109	232	if ( remcap >= exc ) {
jacint@109	233	/A nonsaturating push./
jacint@109	234
jacint@109	235	flow.set(e, flo+exc);
jacint@109	236	excess.set(v, excess.get(v)+exc);
jacint@109	237	exc=0;
jacint@109	238	break;
jacint@109	239
jacint@109	240	} else {
jacint@109	241	/A saturating push./
jacint@109	242
jacint@109	243	flow.set(e, cap);
jacint@109	244	excess.set(v, excess.get(v)+remcap);
jacint@109	245	exc-=remcap;
jacint@109	246	}
jacint@109	247	} else if ( newlevel > level.get(v) ){
jacint@109	248	newlevel = level.get(v);
jacint@109	249	}
jacint@109	250
jacint@109	251	} //for out edges wv
jacint@109	252
jacint@109	253
jacint@109	254	if ( exc > 0 ) {
jacint@109	255	for( InEdgeIt e=G.template first<InEdgeIt>(w); e.valid(); ++e) {
jacint@109	256
jacint@109	257	if( flow.get(e) == 0 ) continue;
jacint@109	258	NodeIt v=G.tail(e);
jacint@109	259	//e=vw
jacint@109	260
jacint@109	261	if( lev > level.get(v) ) {
jacint@109	262	/Push is allowed now/
jacint@109	263
jacint@109	264	if ( excess.get(v)==0 && v!=t && v!=s ) {
jacint@109	265	int lev_v=level.get(v);
jacint@109	266	next.set(v,active[lev_v]);
jacint@109	267	active[lev_v]=v;
jacint@109	268	}
jacint@109	269
jacint@109	270	T flo=flow.get(e);
jacint@109	271
jacint@109	272	if ( flo >= exc ) {
jacint@109	273	/A nonsaturating push./
jacint@109	274
jacint@109	275	flow.set(e, flo-exc);
jacint@109	276	excess.set(v, excess.get(v)+exc);
jacint@109	277	exc=0;
jacint@109	278	break;
jacint@109	279	} else {
jacint@109	280	/A saturating push./
jacint@109	281
jacint@109	282	excess.set(v, excess.get(v)+flo);
jacint@109	283	exc-=flo;
jacint@109	284	flow.set(e,0);
jacint@109	285	}
jacint@109	286	} else if ( newlevel > level.get(v) ) {
jacint@109	287	newlevel = level.get(v);
jacint@109	288	}
jacint@109	289	} //for in edges vw
jacint@109	290
jacint@109	291	} // if w still has excess after the out edge for cycle
jacint@109	292
jacint@109	293	excess.set(w, exc);
jacint@109	294
jacint@109	295	/*
jacint@109	296	Relabel
jacint@109	297	*/
jacint@109	298
jacint@109	299
jacint@109	300	if ( exc > 0 ) {
jacint@109	301	//now 'lev' is the old level of w
jacint@109	302
jacint@109	303	if ( phase ) {
jacint@109	304	level.set(w,++newlevel);
jacint@109	305	next.set(w,active[newlevel]);
jacint@109	306	active[newlevel]=w;
jacint@109	307	b=newlevel;
jacint@109	308	} else {
jacint@109	309	//unlacing starts
jacint@109	310	NodeIt right_n=right.get(w);
jacint@109	311	NodeIt left_n=left.get(w);
jacint@109	312
jacint@109	313	if ( right_n != 0 ) {
jacint@109	314	if ( left_n != 0 ) {
jacint@109	315	right.set(left_n, right_n);
jacint@109	316	left.set(right_n, left_n);
jacint@109	317	} else {
jacint@109	318	level_list[lev]=right_n;
jacint@109	319	left.set(right_n, 0);
jacint@109	320	}
jacint@109	321	} else {
jacint@109	322	if ( left_n != 0 ) {
jacint@109	323	right.set(left_n, 0);
jacint@109	324	} else {
jacint@109	325	level_list[lev]=0;
jacint@109	326
jacint@109	327	}
jacint@109	328	}
jacint@109	329	//unlacing ends
jacint@109	330
jacint@109	331	//gapping starts
jacint@109	332	if ( level_list[lev]==0 ) {
jacint@109	333
jacint@109	334	for (int i=lev; i!=k ; ) {
jacint@109	335	NodeIt v=level_list[++i];
jacint@109	336	while ( v != 0 ) {
jacint@109	337	level.set(v,n);
jacint@109	338	v=right.get(v);
jacint@109	339	}
jacint@109	340	level_list[i]=0;
jacint@109	341	active[i]=0;
jacint@109	342	}
jacint@109	343
jacint@109	344	level.set(w,n);
jacint@109	345	b=lev-1;
jacint@109	346	k=b;
jacint@109	347	//gapping ends
jacint@109	348	} else {
jacint@109	349
jacint@109	350	if ( newlevel == n ) level.set(w,n);
jacint@109	351	else {
jacint@109	352	level.set(w,++newlevel);
jacint@109	353	next.set(w,active[newlevel]);
jacint@109	354	active[newlevel]=w;
jacint@109	355	if ( k < newlevel ) ++k;
jacint@109	356	NodeIt first=level_list[newlevel];
jacint@109	357	if ( first != 0 ) left.set(first,w);
jacint@109	358	right.set(w,first);
jacint@109	359	left.set(w,0);
jacint@109	360	level_list[newlevel]=w;
jacint@109	361	}
jacint@109	362	}
jacint@109	363
jacint@109	364
jacint@109	365	} //phase 0
jacint@109	366
jacint@109	367
jacint@109	368	} // if ( exc > 0 )
jacint@109	369
jacint@109	370
jacint@109	371	} // if stack[b] is nonempty
jacint@109	372
jacint@109	373	} // while(true)
jacint@109	374
jacint@109	375
jacint@109	376	value = excess.get(t);
jacint@109	377	/Max flow value./
jacint@109	378
jacint@109	379	} //void run()
jacint@109	380
jacint@109	381
jacint@109	382
jacint@109	383
jacint@109	384
jacint@109	385	/*
jacint@109	386	Returns the maximum value of a flow.
jacint@109	387	*/
jacint@109	388
jacint@109	389	T maxFlow() {
jacint@109	390	return value;
jacint@109	391	}
jacint@109	392
jacint@109	393
jacint@109	394
jacint@109	395	/*
jacint@109	396	For the maximum flow x found by the algorithm,
jacint@109	397	it returns the flow value on edge e, i.e. x(e).
jacint@109	398	*/
jacint@109	399
jacint@109	400	T flowOnEdge(EdgeIt e) {
jacint@109	401	return flow.get(e);
jacint@109	402	}
jacint@109	403
jacint@109	404
jacint@109	405
jacint@109	406	FlowMap Flow() {
jacint@109	407	return flow;
jacint@109	408	}
jacint@109	409
jacint@109	410
jacint@109	411
jacint@109	412	void Flow(FlowMap& _flow ) {
jacint@109	413	for(EachNodeIt v=G.template first<EachNodeIt>() ; v.valid(); ++v)
jacint@109	414	_flow.set(v,flow.get(v));
jacint@109	415	}
jacint@109	416
jacint@109	417
jacint@109	418
jacint@109	419	/*
jacint@109	420	Returns the minimum min cut, by a bfs from s in the residual graph.
jacint@109	421	*/
jacint@109	422
jacint@109	423	template<typename _CutMap>
jacint@109	424	void minMinCut(_CutMap& M) {
jacint@109	425
jacint@109	426	std::queue<NodeIt> queue;
jacint@109	427
jacint@109	428	M.set(s,true);
jacint@109	429	queue.push(s);
jacint@109	430
jacint@109	431	while (!queue.empty()) {
jacint@109	432	NodeIt w=queue.front();
jacint@109	433	queue.pop();
jacint@109	434
jacint@109	435	for(OutEdgeIt e=G.template first<OutEdgeIt>(w) ; e.valid(); ++e) {
jacint@109	436	NodeIt v=G.head(e);
jacint@109	437	if (!M.get(v) && flow.get(e) < capacity.get(e) ) {
jacint@109	438	queue.push(v);
jacint@109	439	M.set(v, true);
jacint@109	440	}
jacint@109	441	}
jacint@109	442
jacint@109	443	for(InEdgeIt e=G.template first<InEdgeIt>(w) ; e.valid(); ++e) {
jacint@109	444	NodeIt v=G.tail(e);
jacint@109	445	if (!M.get(v) && flow.get(e) > 0 ) {
jacint@109	446	queue.push(v);
jacint@109	447	M.set(v, true);
jacint@109	448	}
jacint@109	449	}
jacint@109	450	}
jacint@109	451	}
jacint@109	452
jacint@109	453
jacint@109	454
jacint@109	455	/*
jacint@109	456	Returns the maximum min cut, by a reverse bfs
jacint@109	457	from t in the residual graph.
jacint@109	458	*/
jacint@109	459
jacint@109	460	template<typename _CutMap>
jacint@109	461	void maxMinCut(_CutMap& M) {
jacint@109	462
jacint@109	463	std::queue<NodeIt> queue;
jacint@109	464
jacint@109	465	M.set(t,true);
jacint@109	466	queue.push(t);
jacint@109	467
jacint@109	468	while (!queue.empty()) {
jacint@109	469	NodeIt w=queue.front();
jacint@109	470	queue.pop();
jacint@109	471
jacint@109	472	for(InEdgeIt e=G.template first<InEdgeIt>(w) ; e.valid(); ++e) {
jacint@109	473	NodeIt v=G.tail(e);
jacint@109	474	if (!M.get(v) && flow.get(e) < capacity.get(e) ) {
jacint@109	475	queue.push(v);
jacint@109	476	M.set(v, true);
jacint@109	477	}
jacint@109	478	}
jacint@109	479
jacint@109	480	for(OutEdgeIt e=G.template first<OutEdgeIt>(w) ; e.valid(); ++e) {
jacint@109	481	NodeIt v=G.head(e);
jacint@109	482	if (!M.get(v) && flow.get(e) > 0 ) {
jacint@109	483	queue.push(v);
jacint@109	484	M.set(v, true);
jacint@109	485	}
jacint@109	486	}
jacint@109	487	}
jacint@109	488
jacint@109	489	for(EachNodeIt v=G.template first<EachNodeIt>() ; v.valid(); ++v) {
jacint@109	490	M.set(v, !M.get(v));
jacint@109	491	}
jacint@109	492
jacint@109	493	}
jacint@109	494
jacint@109	495
jacint@109	496
jacint@109	497	template<typename _CutMap>
jacint@109	498	void minCut(_CutMap& M) {
jacint@109	499	minMinCut(M);
jacint@109	500	}
jacint@109	501
jacint@109	502	};
jacint@109	503	}//namespace marci
jacint@109	504	#endif
jacint@109	505
jacint@109	506
jacint@109	507
jacint@109	508

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