lemon-0.x: src/work/jacint/preflow.h@01d47457aff3 (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@113	11	runs heuristic 'bound 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@113	47	#include <time_measure.h>
jacint@113	48
jacint@109	49	namespace hugo {
jacint@109	50
jacint@109	51	template <typename Graph, typename T,
jacint@109	52	typename FlowMap=typename Graph::EdgeMap<T>,
jacint@109	53	typename CapMap=typename Graph::EdgeMap<T> >
jacint@109	54	class preflow {
jacint@109	55
jacint@109	56	typedef typename Graph::NodeIt NodeIt;
jacint@109	57	typedef typename Graph::EdgeIt EdgeIt;
jacint@109	58	typedef typename Graph::EachNodeIt EachNodeIt;
jacint@109	59	typedef typename Graph::OutEdgeIt OutEdgeIt;
jacint@109	60	typedef typename Graph::InEdgeIt InEdgeIt;
jacint@109	61
jacint@109	62	Graph& G;
jacint@109	63	NodeIt s;
jacint@109	64	NodeIt t;
jacint@109	65	FlowMap flow;
jacint@109	66	CapMap& capacity;
jacint@109	67	T value;
jacint@109	68
jacint@109	69	public:
jacint@113	70	double time;
jacint@109	71	preflow(Graph& _G, NodeIt _s, NodeIt _t, CapMap& _capacity ) :
jacint@109	72	G(_G), s(_s), t(_t), flow(_G, 0), capacity(_capacity)
jacint@109	73	{
jacint@109	74
jacint@109	75	bool phase=0; //phase 0 is the 1st phase, phase 1 is the 2nd
jacint@109	76	int n=G.nodeNum();
jacint@109	77	int heur0=(int)(H0*n); //time while running 'bound decrease'
jacint@109	78	int heur1=(int)(H1*n); //time while running 'highest label'
jacint@109	79	int heur=heur1; //starting time interval (#of relabels)
jacint@109	80	bool what_heur=1;
jacint@109	81	/*
jacint@109	82	what_heur is 0 in case 'bound decrease'
jacint@109	83	and 1 in case 'highest label'
jacint@109	84	*/
jacint@109	85	bool end=false;
jacint@109	86	/*
jacint@109	87	Needed for 'bound decrease', 'true'
jacint@109	88	means no active nodes are above bound b.
jacint@109	89	*/
jacint@109	90	int relabel=0;
jacint@109	91	int k=n-2; //bound on the highest level under n containing a node
jacint@109	92	int b=k; //bound on the highest level under n of an active node
jacint@109	93
jacint@109	94	typename Graph::NodeMap<int> level(G,n);
jacint@109	95	typename Graph::NodeMap<T> excess(G);
jacint@109	96
jacint@109	97	std::vector<NodeIt> active(n);
jacint@109	98	typename Graph::NodeMap<NodeIt> next(G);
jacint@109	99	//Stack of the active nodes in level i < n.
jacint@109	100	//We use it in both phases.
jacint@109	101
jacint@109	102	typename Graph::NodeMap<NodeIt> left(G);
jacint@109	103	typename Graph::NodeMap<NodeIt> right(G);
jacint@109	104	std::vector<NodeIt> level_list(n);
jacint@109	105	/*
jacint@109	106	List of the nodes in level i<n.
jacint@109	107	*/
jacint@109	108
jacint@109	109	/Reverse_bfs from t, to find the starting level./
jacint@109	110	level.set(t,0);
jacint@109	111	std::queue<NodeIt> bfs_queue;
jacint@109	112	bfs_queue.push(t);
jacint@109	113
jacint@109	114	while (!bfs_queue.empty()) {
jacint@109	115
jacint@109	116	NodeIt v=bfs_queue.front();
jacint@109	117	bfs_queue.pop();
jacint@109	118	int l=level.get(v)+1;
jacint@109	119
jacint@109	120	for(InEdgeIt e=G.template first<InEdgeIt>(v); e.valid(); ++e) {
jacint@109	121	NodeIt w=G.tail(e);
jacint@109	122	if ( level.get(w) == n && w != s ) {
jacint@109	123	bfs_queue.push(w);
jacint@109	124	NodeIt first=level_list[l];
jacint@109	125	if ( first != 0 ) left.set(first,w);
jacint@109	126	right.set(w,first);
jacint@109	127	level_list[l]=w;
jacint@109	128	level.set(w, l);
jacint@109	129	}
jacint@109	130	}
jacint@109	131	}
jacint@109	132
jacint@109	133	level.set(s,n);
jacint@109	134
jacint@109	135
jacint@109	136	/* Starting flow. It is everywhere 0 at the moment. */
jacint@109	137	for(OutEdgeIt e=G.template first<OutEdgeIt>(s); e.valid(); ++e)
jacint@109	138	{
jacint@109	139	T c=capacity.get(e);
jacint@109	140	if ( c == 0 ) continue;
jacint@109	141	NodeIt w=G.head(e);
jacint@109	142	if ( level.get(w) < n ) {
jacint@109	143	if ( excess.get(w) == 0 && w!=t ) {
jacint@109	144	next.set(w,active[level.get(w)]);
jacint@109	145	active[level.get(w)]=w;
jacint@109	146	}
jacint@109	147	flow.set(e, c);
jacint@109	148	excess.set(w, excess.get(w)+c);
jacint@109	149	}
jacint@109	150	}
jacint@109	151
jacint@109	152	/*
jacint@109	153	End of preprocessing
jacint@109	154	*/
jacint@109	155
jacint@109	156
jacint@109	157
jacint@109	158	/*
jacint@109	159	Push/relabel on the highest level active nodes.
jacint@109	160	*/
jacint@109	161	while ( true ) {
jacint@109	162
jacint@109	163	if ( b == 0 ) {
jacint@109	164	if ( phase ) break;
jacint@109	165
jacint@109	166	if ( !what_heur && !end && k > 0 ) {
jacint@109	167	b=k;
jacint@109	168	end=true;
jacint@109	169	} else {
jacint@109	170	phase=1;
jacint@113	171	time=currTime();
jacint@109	172	level.set(s,0);
jacint@109	173	std::queue<NodeIt> bfs_queue;
jacint@109	174	bfs_queue.push(s);
jacint@109	175
jacint@109	176	while (!bfs_queue.empty()) {
jacint@109	177
jacint@109	178	NodeIt v=bfs_queue.front();
jacint@109	179	bfs_queue.pop();
jacint@109	180	int l=level.get(v)+1;
jacint@109	181
jacint@109	182	for(InEdgeIt e=G.template first<InEdgeIt>(v); e.valid(); ++e) {
jacint@109	183	if ( capacity.get(e) == flow.get(e) ) continue;
jacint@109	184	NodeIt u=G.tail(e);
jacint@109	185	if ( level.get(u) >= n ) {
jacint@109	186	bfs_queue.push(u);
jacint@109	187	level.set(u, l);
jacint@109	188	if ( excess.get(u) > 0 ) {
jacint@109	189	next.set(u,active[l]);
jacint@109	190	active[l]=u;
jacint@109	191	}
jacint@109	192	}
jacint@109	193	}
jacint@109	194
jacint@109	195	for(OutEdgeIt e=G.template first<OutEdgeIt>(v); e.valid(); ++e) {
jacint@109	196	if ( 0 == flow.get(e) ) continue;
jacint@109	197	NodeIt u=G.head(e);
jacint@109	198	if ( level.get(u) >= n ) {
jacint@109	199	bfs_queue.push(u);
jacint@109	200	level.set(u, l);
jacint@109	201	if ( excess.get(u) > 0 ) {
jacint@109	202	next.set(u,active[l]);
jacint@109	203	active[l]=u;
jacint@109	204	}
jacint@109	205	}
jacint@109	206	}
jacint@109	207	}
jacint@109	208	b=n-2;
jacint@109	209	}
jacint@109	210
jacint@109	211	}
jacint@109	212
jacint@109	213
jacint@109	214	if ( active[b] == 0 ) --b;
jacint@109	215	else {
jacint@109	216	end=false;
jacint@109	217
jacint@109	218	NodeIt w=active[b];
jacint@109	219	active[b]=next.get(w);
jacint@109	220	int lev=level.get(w);
jacint@109	221	T exc=excess.get(w);
jacint@109	222	int newlevel=n; //bound on the next level of w
jacint@109	223
jacint@109	224	for(OutEdgeIt e=G.template first<OutEdgeIt>(w); e.valid(); ++e) {
jacint@109	225
jacint@109	226	if ( flow.get(e) == capacity.get(e) ) continue;
jacint@109	227	NodeIt v=G.head(e);
jacint@109	228	//e=wv
jacint@109	229
jacint@109	230	if( lev > level.get(v) ) {
jacint@109	231	/Push is allowed now/
jacint@109	232
jacint@109	233	if ( excess.get(v)==0 && v!=t && v!=s ) {
jacint@109	234	int lev_v=level.get(v);
jacint@109	235	next.set(v,active[lev_v]);
jacint@109	236	active[lev_v]=v;
jacint@109	237	}
jacint@109	238
jacint@109	239	T cap=capacity.get(e);
jacint@109	240	T flo=flow.get(e);
jacint@109	241	T remcap=cap-flo;
jacint@109	242
jacint@109	243	if ( remcap >= exc ) {
jacint@109	244	/A nonsaturating push./
jacint@109	245
jacint@109	246	flow.set(e, flo+exc);
jacint@109	247	excess.set(v, excess.get(v)+exc);
jacint@109	248	exc=0;
jacint@109	249	break;
jacint@109	250
jacint@109	251	} else {
jacint@109	252	/A saturating push./
jacint@109	253
jacint@109	254	flow.set(e, cap);
jacint@109	255	excess.set(v, excess.get(v)+remcap);
jacint@109	256	exc-=remcap;
jacint@109	257	}
jacint@109	258	} else if ( newlevel > level.get(v) ){
jacint@109	259	newlevel = level.get(v);
jacint@109	260	}
jacint@109	261
jacint@109	262	} //for out edges wv
jacint@109	263
jacint@109	264
jacint@109	265	if ( exc > 0 ) {
jacint@109	266	for( InEdgeIt e=G.template first<InEdgeIt>(w); e.valid(); ++e) {
jacint@109	267
jacint@109	268	if( flow.get(e) == 0 ) continue;
jacint@109	269	NodeIt v=G.tail(e);
jacint@109	270	//e=vw
jacint@109	271
jacint@109	272	if( lev > level.get(v) ) {
jacint@109	273	/Push is allowed now/
jacint@109	274
jacint@109	275	if ( excess.get(v)==0 && v!=t && v!=s ) {
jacint@109	276	int lev_v=level.get(v);
jacint@109	277	next.set(v,active[lev_v]);
jacint@109	278	active[lev_v]=v;
jacint@109	279	}
jacint@109	280
jacint@109	281	T flo=flow.get(e);
jacint@109	282
jacint@109	283	if ( flo >= exc ) {
jacint@109	284	/A nonsaturating push./
jacint@109	285
jacint@109	286	flow.set(e, flo-exc);
jacint@109	287	excess.set(v, excess.get(v)+exc);
jacint@109	288	exc=0;
jacint@109	289	break;
jacint@109	290	} else {
jacint@109	291	/A saturating push./
jacint@109	292
jacint@109	293	excess.set(v, excess.get(v)+flo);
jacint@109	294	exc-=flo;
jacint@109	295	flow.set(e,0);
jacint@109	296	}
jacint@109	297	} else if ( newlevel > level.get(v) ) {
jacint@109	298	newlevel = level.get(v);
jacint@109	299	}
jacint@109	300	} //for in edges vw
jacint@109	301
jacint@109	302	} // if w still has excess after the out edge for cycle
jacint@109	303
jacint@109	304	excess.set(w, exc);
jacint@109	305
jacint@109	306	/*
jacint@109	307	Relabel
jacint@109	308	*/
jacint@109	309
jacint@109	310
jacint@109	311	if ( exc > 0 ) {
jacint@109	312	//now 'lev' is the old level of w
jacint@109	313
jacint@109	314	if ( phase ) {
jacint@109	315	level.set(w,++newlevel);
jacint@109	316	next.set(w,active[newlevel]);
jacint@109	317	active[newlevel]=w;
jacint@109	318	b=newlevel;
jacint@109	319	} else {
jacint@109	320	//unlacing starts
jacint@109	321	NodeIt right_n=right.get(w);
jacint@109	322	NodeIt left_n=left.get(w);
jacint@109	323
jacint@109	324	if ( right_n != 0 ) {
jacint@109	325	if ( left_n != 0 ) {
jacint@109	326	right.set(left_n, right_n);
jacint@109	327	left.set(right_n, left_n);
jacint@109	328	} else {
jacint@109	329	level_list[lev]=right_n;
jacint@109	330	left.set(right_n, 0);
jacint@109	331	}
jacint@109	332	} else {
jacint@109	333	if ( left_n != 0 ) {
jacint@109	334	right.set(left_n, 0);
jacint@109	335	} else {
jacint@109	336	level_list[lev]=0;
jacint@109	337
jacint@109	338	}
jacint@109	339	}
jacint@109	340	//unlacing ends
jacint@109	341
jacint@109	342	//gapping starts
jacint@109	343	if ( level_list[lev]==0 ) {
jacint@109	344
jacint@109	345	for (int i=lev; i!=k ; ) {
jacint@109	346	NodeIt v=level_list[++i];
jacint@109	347	while ( v != 0 ) {
jacint@109	348	level.set(v,n);
jacint@109	349	v=right.get(v);
jacint@109	350	}
jacint@109	351	level_list[i]=0;
jacint@109	352	if ( !what_heur ) active[i]=0;
jacint@109	353	}
jacint@109	354
jacint@109	355	level.set(w,n);
jacint@109	356	b=lev-1;
jacint@109	357	k=b;
jacint@109	358	//gapping ends
jacint@109	359	} else {
jacint@109	360
jacint@109	361	if ( newlevel == n ) level.set(w,n);
jacint@109	362	else {
jacint@109	363	level.set(w,++newlevel);
jacint@109	364	next.set(w,active[newlevel]);
jacint@109	365	active[newlevel]=w;
jacint@109	366	if ( what_heur ) b=newlevel;
jacint@109	367	if ( k < newlevel ) ++k;
jacint@109	368	NodeIt first=level_list[newlevel];
jacint@109	369	if ( first != 0 ) left.set(first,w);
jacint@109	370	right.set(w,first);
jacint@109	371	left.set(w,0);
jacint@109	372	level_list[newlevel]=w;
jacint@109	373	}
jacint@109	374	}
jacint@109	375
jacint@109	376
jacint@109	377	++relabel;
jacint@109	378	if ( relabel >= heur ) {
jacint@109	379	relabel=0;
jacint@109	380	if ( what_heur ) {
jacint@109	381	what_heur=0;
jacint@109	382	heur=heur0;
jacint@109	383	end=false;
jacint@109	384	} else {
jacint@109	385	what_heur=1;
jacint@109	386	heur=heur1;
jacint@109	387	b=k;
jacint@109	388	}
jacint@109	389	}
jacint@109	390	} //phase 0
jacint@109	391
jacint@109	392
jacint@109	393	} // if ( exc > 0 )
jacint@109	394
jacint@109	395
jacint@109	396	} // if stack[b] is nonempty
jacint@109	397
jacint@109	398	} // while(true)
jacint@109	399
jacint@109	400
jacint@109	401	value = excess.get(t);
jacint@109	402	/Max flow value./
jacint@109	403
jacint@109	404	} //void run()
jacint@109	405
jacint@109	406
jacint@109	407
jacint@109	408
jacint@109	409
jacint@109	410	/*
jacint@109	411	Returns the maximum value of a flow.
jacint@109	412	*/
jacint@109	413
jacint@109	414	T maxFlow() {
jacint@109	415	return value;
jacint@109	416	}
jacint@109	417
jacint@109	418
jacint@109	419
jacint@109	420	/*
jacint@109	421	For the maximum flow x found by the algorithm,
jacint@109	422	it returns the flow value on edge e, i.e. x(e).
jacint@109	423	*/
jacint@109	424
jacint@109	425	T flowOnEdge(EdgeIt e) {
jacint@109	426	return flow.get(e);
jacint@109	427	}
jacint@109	428
jacint@109	429
jacint@109	430
jacint@109	431	FlowMap Flow() {
jacint@109	432	return flow;
jacint@109	433	}
jacint@109	434
jacint@109	435
jacint@109	436
jacint@109	437	void Flow(FlowMap& _flow ) {
jacint@109	438	for(EachNodeIt v=G.template first<EachNodeIt>() ; v.valid(); ++v)
jacint@109	439	_flow.set(v,flow.get(v));
jacint@109	440	}
jacint@109	441
jacint@109	442
jacint@109	443
jacint@109	444	/*
jacint@109	445	Returns the minimum min cut, by a bfs from s in the residual graph.
jacint@109	446	*/
jacint@109	447
jacint@109	448	template<typename _CutMap>
jacint@109	449	void minMinCut(_CutMap& M) {
jacint@109	450
jacint@109	451	std::queue<NodeIt> queue;
jacint@109	452
jacint@109	453	M.set(s,true);
jacint@109	454	queue.push(s);
jacint@109	455
jacint@109	456	while (!queue.empty()) {
jacint@109	457	NodeIt w=queue.front();
jacint@109	458	queue.pop();
jacint@109	459
jacint@109	460	for(OutEdgeIt e=G.template first<OutEdgeIt>(w) ; e.valid(); ++e) {
jacint@109	461	NodeIt v=G.head(e);
jacint@109	462	if (!M.get(v) && flow.get(e) < capacity.get(e) ) {
jacint@109	463	queue.push(v);
jacint@109	464	M.set(v, true);
jacint@109	465	}
jacint@109	466	}
jacint@109	467
jacint@109	468	for(InEdgeIt e=G.template first<InEdgeIt>(w) ; e.valid(); ++e) {
jacint@109	469	NodeIt v=G.tail(e);
jacint@109	470	if (!M.get(v) && flow.get(e) > 0 ) {
jacint@109	471	queue.push(v);
jacint@109	472	M.set(v, true);
jacint@109	473	}
jacint@109	474	}
jacint@109	475	}
jacint@109	476	}
jacint@109	477
jacint@109	478
jacint@109	479
jacint@109	480	/*
jacint@109	481	Returns the maximum min cut, by a reverse bfs
jacint@109	482	from t in the residual graph.
jacint@109	483	*/
jacint@109	484
jacint@109	485	template<typename _CutMap>
jacint@109	486	void maxMinCut(_CutMap& M) {
jacint@109	487
jacint@109	488	std::queue<NodeIt> queue;
jacint@109	489
jacint@109	490	M.set(t,true);
jacint@109	491	queue.push(t);
jacint@109	492
jacint@109	493	while (!queue.empty()) {
jacint@109	494	NodeIt w=queue.front();
jacint@109	495	queue.pop();
jacint@109	496
jacint@109	497	for(InEdgeIt e=G.template first<InEdgeIt>(w) ; e.valid(); ++e) {
jacint@109	498	NodeIt v=G.tail(e);
jacint@109	499	if (!M.get(v) && flow.get(e) < capacity.get(e) ) {
jacint@109	500	queue.push(v);
jacint@109	501	M.set(v, true);
jacint@109	502	}
jacint@109	503	}
jacint@109	504
jacint@109	505	for(OutEdgeIt e=G.template first<OutEdgeIt>(w) ; e.valid(); ++e) {
jacint@109	506	NodeIt v=G.head(e);
jacint@109	507	if (!M.get(v) && flow.get(e) > 0 ) {
jacint@109	508	queue.push(v);
jacint@109	509	M.set(v, true);
jacint@109	510	}
jacint@109	511	}
jacint@109	512	}
jacint@109	513
jacint@109	514	for(EachNodeIt v=G.template first<EachNodeIt>() ; v.valid(); ++v) {
jacint@109	515	M.set(v, !M.get(v));
jacint@109	516	}
jacint@109	517
jacint@109	518	}
jacint@109	519
jacint@109	520
jacint@109	521
jacint@109	522	template<typename CutMap>
jacint@109	523	void minCut(CutMap& M) {
jacint@109	524	minMinCut(M);
jacint@109	525	}
jacint@109	526
jacint@109	527
jacint@109	528	};
jacint@109	529	}//namespace marci
jacint@109	530	#endif
jacint@109	531
jacint@109	532
jacint@109	533
jacint@109	534

author	jacint
	Mon, 01 Mar 2004 17:24:34 +0000
changeset 142	01d47457aff3
parent 109	fc5982b39e10
child 174	44700ed9ffaa
permissions	-rw-r--r--