diff -r 0f1aacd7867b -r cbdb54e46d96 src/work/jacint/preflow_push_hl.hh --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/work/jacint/preflow_push_hl.hh Fri Jan 30 14:53:17 2004 +0000 @@ -0,0 +1,320 @@ +/* +preflow_push_hl.hh +by jacint. +Runs the highest label variant of the preflow push algorithm with +running time O(n^2\sqrt(m)). + +Member functions: + +void run() : runs the algorithm + + The following functions should be used after run() was already run. + +T maxflow() : returns the value of a maximum flow + +T flowonedge(edge_iterator e) : for a fixed maximum flow x it returns x(e) + +edge_property_vector allflow() : returns the fixed maximum flow x + +node_property_vector mincut() : returns a + characteristic vector of a minimum cut. (An empty level + in the algorithm gives a minimum cut.) +*/ + +#ifndef PREFLOW_PUSH_HL_HH +#define PREFLOW_PUSH_HL_HH + +#include +#include +#include + +#include +#include +#include + +namespace marci { + + template + class preflow_push_hl { + + typedef typename graph_traits::node_iterator node_iterator; + typedef typename graph_traits::edge_iterator edge_iterator; + typedef typename graph_traits::each_node_iterator each_node_iterator; + typedef typename graph_traits::out_edge_iterator out_edge_iterator; + typedef typename graph_traits::in_edge_iterator in_edge_iterator; + typedef typename graph_traits::each_edge_iterator each_edge_iterator; + + + graph_type& G; + node_iterator s; + node_iterator t; + edge_property_vector flow; + edge_property_vector& capacity; + T value; + node_property_vector mincutvector; + + + public: + + preflow_push_hl(graph_type& _G, node_iterator _s, node_iterator _t, edge_property_vector& _capacity) : G(_G), s(_s), t(_t), flow(_G, 0), capacity(_capacity), mincutvector(_G, true) { } + + + + + /* + The run() function runs the highest label preflow-push, + running time: O(n^2\sqrt(m)) + */ + void run() { + + node_property_vector level(G); //level of node + node_property_vector excess(G); //excess of node + + int n=number_of(G.first_node()); //number of nodes + int b=n; + /*b is a bound on the highest level of an active node. In the beginning it is at most n-2.*/ + + std::vector > stack(2*n-1); //Stack of the active nodes in level i. + + + + + /*Reverse_bfs from t, to find the starting level.*/ + + reverse_bfs bfs(G, t); + bfs.run(); + for(each_node_iterator v=G.first_node(); v.valid(); ++v) { + level.put(v, bfs.dist(v)); + //std::cout << "the level of " << v << " is " << bfs.dist(v); + } + + /*The level of s is fixed to n*/ + level.put(s,n); + + + + + + /* Starting flow. It is everywhere 0 at the moment. */ + + for(out_edge_iterator i=G.first_out_edge(s); i.valid(); ++i) + { + node_iterator w=G.head(i); + flow.put(i, capacity.get(i)); + stack[bfs.dist(w)].push(w); + excess.put(w, capacity.get(i)); + } + + + /* + End of preprocessing + */ + + + + /* + Push/relabel on the highest level active nodes. + */ + + /*While there exists active node.*/ + while (b) { + + /*We decrease the bound if there is no active node of level b.*/ + if (stack[b].empty()) { + --b; + } else { + + node_iterator w=stack[b].top(); //w is the highest label active node. + stack[b].pop(); //We delete w from the stack. + + int newlevel=2*n-2; //In newlevel we maintain the next level of w. + + for(out_edge_iterator e=G.first_out_edge(w); e.valid(); ++e) { + node_iterator v=G.head(e); + /*e is the edge wv.*/ + + if (flow.get(e) excess.get(w)) { + /*A nonsaturating push.*/ + + if (excess.get(v)==0 && v != s) stack[level.get(v)].push(v); + /*v becomes active.*/ + + flow.put(e, flow.get(e)+excess.get(w)); + excess.put(v, excess.get(v)+excess.get(w)); + excess.put(w,0); + //std::cout << w << " " << v <<" elore elen nonsat pump " << std::endl; + break; + } else { + /*A saturating push.*/ + + if (excess.get(v)==0 && v != s) stack[level.get(v)].push(v); + /*v becomes active.*/ + + excess.put(v, excess.get(v)+capacity.get(e)-flow.get(e)); + excess.put(w, excess.get(w)-capacity.get(e)+flow.get(e)); + flow.put(e, capacity.get(e)); + //std::cout << w<<" " < excess.get(w)) + } // if(level.get(w)==level.get(v)+1) + + else {newlevel = newlevel < level.get(v) ? newlevel : level.get(v);} + + } //if (flow.get(e)0) { + /*e is an edge of the residual graph */ + + if(level.get(w)==level.get(v)+1) { + /*Push is allowed now*/ + + if (flow.get(e) > excess.get(w)) { + /*A nonsaturating push.*/ + + if (excess.get(v)==0 && v != s) stack[level.get(v)].push(v); + /*v becomes active.*/ + + flow.put(e, flow.get(e)-excess.get(w)); + excess.put(v, excess.get(v)+excess.get(w)); + excess.put(w,0); + //std::cout << v << " " << w << " vissza elen nonsat pump " << std::endl; + break; + } else { + /*A saturating push.*/ + + if (excess.get(v)==0 && v != s) stack[level.get(v)].push(v); + /*v becomes active.*/ + + excess.put(v, excess.get(v)+flow.get(e)); + excess.put(w, excess.get(w)-flow.get(e)); + flow.put(e,0); + //std::cout << v <<" " << w << " vissza elen sat pump " << std::endl; + if (excess.get(w)==0) { break;} + } //if (flow.get(e) > excess.get(v)) + } //if(level.get(w)==level.get(v)+1) + + else {newlevel = newlevel < level.get(v) ? newlevel : level.get(v);} + + + } //if (flow.get(e)>0) + + } //for + + + if (excess.get(w)>0) { + level.put(w,++newlevel); + stack[newlevel].push(w); + b=newlevel; + //std::cout << "The new level of " << w << " is "<< newlevel < allflow() { + return flow; + } + + + + /* + Returns a minimum cut by using a reverse bfs from t in the residual graph. + */ + + node_property_vector mincut() { + + std::queue queue; + + mincutvector.put(t,false); + queue.push(t); + + while (!queue.empty()) { + node_iterator w=queue.front(); + queue.pop(); + + for(in_edge_iterator e=G.first_in_edge(w) ; e.valid(); ++e) { + node_iterator v=G.tail(e); + if (mincutvector.get(v) && flow.get(e) < capacity.get(e) ) { + queue.push(v); + mincutvector.put(v, false); + } + } // for + + for(out_edge_iterator e=G.first_out_edge(w) ; e.valid(); ++e) { + node_iterator v=G.head(e); + if (mincutvector.get(v) && flow.get(e) > 0 ) { + queue.push(v); + mincutvector.put(v, false); + } + } // for + + } + + return mincutvector; + + } + + + }; +}//namespace marci +#endif + + + +