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mcmf.cpp
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mcmf.cpp
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#include "mcmf.h"
#include <string.h>
using namespace std;
////////////////////////////////////////////////////////////////////////////////
//
// MCMF_CS2
//
////////////////////////////////////////////////////////////////////////////////
#define WHITE 0
#define GREY 1
#define BLACK 2
#define OPEN( a ) ( a->rez_capacity() > 0 )
#define CLOSED( a ) ( a->rez_capacity() <= 0 )
#define REDUCED_COST( i, j, a ) ( i->price() + a->cost() - j->price() )
#define FEASIBLE( i, j, a ) ( i->price() + a->cost() < j->price() )
#define ADMISSIBLE( i, j, a ) ( OPEN( a ) && FEASIBLE( i, j, a ) )
#define SUSPENDED( i, a ) ( a < i->first() )
#define REMOVE_FROM_EXCESS_Q( i ) \
{ \
i = _excq_first; \
_excq_first = i -> q_next(); \
i ->set_q_next( _sentinel_node ); \
}
#define STACKQ_POP( i ) \
{ \
i = _excq_first; \
_excq_first = i -> q_next(); \
i ->set_q_next( _sentinel_node ); \
}
#define GET_FROM_BUCKET( i, b ) \
{ \
i = ( b -> p_first() ); \
b ->set_p_first( i -> b_next() ); \
}
#define REMOVE_FROM_BUCKET( i, b ) \
{ \
if ( i == ( b -> p_first() ) ) \
b ->set_p_first( i -> b_next() ); \
else \
{ \
( i -> b_prev() )->set_b_next( i -> b_next() ); \
( i -> b_next() )->set_b_prev( i -> b_prev() ); \
} \
}
void MCMF_CS2::err_end( int cc)
{
// abnormal finish
printf ("\nError %d\n", cc );
// 2 - problem is unfeasible
// 5 - allocation fault
// 6 - price overflow
exit( cc);
}
void MCMF_CS2::allocate_arrays()
{
// (1) allocate memory for 'nodes', 'arcs' and internal arrays;
_nodes = (NODE*) calloc ( _n+2, sizeof(NODE) );
_arcs = (ARC*) calloc ( 2*_m+1, sizeof(ARC) );
_cap = (long*) calloc ( 2*_m, sizeof(long) );
_arc_tail = (long*) calloc ( 2*_m, sizeof(long) );
_arc_first = (long*) calloc ( _n+2, sizeof(long) );
// arc_first [ 0 .. n+1 ] = 0 - initialized by calloc;
for ( NODE *in = _nodes; in <= _nodes + _n; in ++ ) {
in->set_excess( 0);
}
if ( _nodes == NULL || _arcs == NULL || _arc_first == NULL || _arc_tail == NULL) {
printf("Error: Memory allocation problem inside CS2\n");
exit( 1);
}
// (2) resets;
_pos_current = 0;
_arc_current = _arcs; // set "current" pointer to the first arc
_node_max = 0;
_node_min = _n;
_max_cost = 0;
_total_p = _total_n = 0;
// at this moment we are ready to add arcs and build the network,
// by using set_arc()...
}
void MCMF_CS2::deallocate_arrays()
{
if ( _arcs) free ( _arcs );
if ( _dnode) delete _dnode;
if ( _cap) free ( _cap );
if ( _buckets) free ( _buckets );
if ( _check_solution == true) free ( _node_balance );
if ( _nodes) {
_nodes = _nodes - _node_min;
free ( _nodes );
}
}
void MCMF_CS2::set_arc( long tail_node_id, long head_node_id,
long low_bound, long up_bound, // up_bound is basically capacity;
price_t cost)
{
// DIMACS format:
// c arc has <tail> <head> <capacity l.b.> <capacity u.b> <cost>
if ( tail_node_id < 0 || tail_node_id > _n ||
head_node_id < 0 || head_node_id > _n ) {
printf("Error: Arc with head or tail out of bounds inside CS2\n");
exit( 1);
}
if ( up_bound < 0 ) {
up_bound = MAX_32;
printf("Warning: Infinite capacity replaced by BIGGEST_FLOW\n");
}
if ( low_bound < 0 || low_bound > up_bound ) {
printf("Error: Wrong capacity bounds inside CS2\n");
exit( 1);
}
// no of arcs incident to node i is placed in _arc_first[i+1]
_arc_first[tail_node_id + 1] ++;
_arc_first[head_node_id + 1] ++;
_i_node = _nodes + tail_node_id;
_j_node = _nodes + head_node_id;
// store information about the arc
_arc_tail[_pos_current] = tail_node_id;
_arc_tail[_pos_current+1] = head_node_id;
_arc_current->set_head( _j_node );
_arc_current->set_rez_capacity( up_bound - low_bound );
_cap[_pos_current] = up_bound;
_arc_current->set_cost( cost );
_arc_current->set_sister( _arc_current + 1 );
( _arc_current + 1 )->set_head( _nodes + tail_node_id );
( _arc_current + 1 )->set_rez_capacity( 0 );
_cap[_pos_current+1] = 0;
( _arc_current + 1 )->set_cost( -cost );
( _arc_current + 1 )->set_sister( _arc_current );
_i_node->dec_excess( low_bound );
_j_node->inc_excess( low_bound );
// searching for minimum and maximum node
if ( head_node_id < _node_min ) _node_min = head_node_id;
if ( tail_node_id < _node_min ) _node_min = tail_node_id;
if ( head_node_id > _node_max ) _node_max = head_node_id;
if ( tail_node_id > _node_max ) _node_max = tail_node_id;
if ( cost < 0 ) cost = -cost;
if ( cost > _max_cost && up_bound > 0 ) _max_cost = cost;
// prepare for next arc to be added;
_arc_current += 2;
_pos_current += 2;
}
void MCMF_CS2::set_supply_demand_of_node( long id, long excess)
{
// set supply and demand of nodes; not used for transhipment nodes;
if ( id < 0 || id > _n ) {
printf("Error: Unbalanced problem inside CS2\n");
exit( 1);
}
(_nodes + id)->set_excess( excess);
if ( excess > 0) _total_p += excess;
if ( excess < 0) _total_n -= excess;
}
void MCMF_CS2::pre_processing()
{
// called after the arcs were just added and before run_cs2();
// ordering arcs - linear time algorithm;
long i;
long last, arc_num, arc_new_num;;
long tail_node_id;
NODE *head_p;
ARC *arc_new, *arc_tmp;
long up_bound;
price_t cost; // arc cost;
excess_t cap_out; // sum of outgoing capacities
excess_t cap_in; // sum of incoming capacities
if ( ABS( _total_p - _total_n ) > 0.5 ) {
printf("Error: Unbalanced problem inside CS2\n");
exit( 1);
}
// first arc from the first node
( _nodes + _node_min )->set_first( _arcs );
// before below loop arc_first[i+1] is the number of arcs outgoing from i;
// after this loop arc_first[i] is the position of the first
// outgoing from node i arcs after they would be ordered;
// this value is transformed to pointer and written to node.first[i]
for ( i = _node_min + 1; i <= _node_max + 1; i ++ ) {
_arc_first[i] += _arc_first[i-1];
( _nodes + i )->set_first( _arcs + _arc_first[i] );
}
// scanning all the nodes except the last
for ( i = _node_min; i < _node_max; i ++ ) {
last = ( ( _nodes + i + 1 )->first() ) - _arcs;
// arcs outgoing from i must be cited
// from position arc_first[i] to the position
// equal to initial value of arc_first[i+1]-1
for ( arc_num = _arc_first[i]; arc_num < last; arc_num ++ ) {
tail_node_id = _arc_tail[arc_num];
while ( tail_node_id != i ) {
// the arc no arc_num is not in place because arc cited here
// must go out from i;
// we'll put it to its place and continue this process
// until an arc in this position would go out from i
arc_new_num = _arc_first[tail_node_id];
_arc_current = _arcs + arc_num;
arc_new = _arcs + arc_new_num;
// arc_current must be cited in the position arc_new
// swapping these arcs:
head_p = arc_new->head();
arc_new->set_head( _arc_current->head() );
_arc_current->set_head( head_p );
up_bound = _cap[arc_new_num];
_cap[arc_new_num] = _cap[arc_num];
_cap[arc_num] = up_bound;
up_bound = arc_new->rez_capacity();
arc_new->set_rez_capacity( _arc_current->rez_capacity() );
_arc_current->set_rez_capacity( up_bound) ;
cost = arc_new->cost();
arc_new->set_cost( _arc_current->cost() );
_arc_current->set_cost( cost );
if ( arc_new != _arc_current->sister() ) {
arc_tmp = arc_new->sister();
arc_new->set_sister( _arc_current->sister() );
_arc_current->set_sister( arc_tmp );
_arc_current->sister()->set_sister( _arc_current );
arc_new->sister()->set_sister( arc_new );
}
_arc_tail[arc_num] = _arc_tail[arc_new_num];
_arc_tail[arc_new_num] = tail_node_id;
// we increase arc_first[tail_node_id]
_arc_first[tail_node_id] ++ ;
tail_node_id = _arc_tail[arc_num];
}
}
// all arcs outgoing from i are in place
}
// arcs are ordered by now!
// testing network for possible excess overflow
for ( NODE *ndp = _nodes + _node_min; ndp <= _nodes + _node_max; ndp ++ ) {
cap_in = ( ndp->excess() );
cap_out = - ( ndp->excess() );
for ( _arc_current = ndp->first(); _arc_current != (ndp+1)->first();
_arc_current ++ ) {
arc_num = _arc_current - _arcs;
if ( _cap[arc_num] > 0 ) cap_out += _cap[arc_num];
if ( _cap[arc_num] == 0 )
cap_in += _cap[ _arc_current->sister() - _arcs ];
}
}
if ( _node_min < 0 || _node_min > 1 ) {
printf("Error: Node ids must start from 0 or 1 inside CS2\n");
exit( 1);
}
// adjustments due to nodes' ids being between _node_min - _node_max;
_n = _node_max - _node_min + 1;
_nodes = _nodes + _node_min;
// () free internal memory, not needed anymore inside CS2;
free ( _arc_first );
free ( _arc_tail );
}
void MCMF_CS2::cs2_initialize()
{
// initialization;
// called after allocate_arrays() and all nodes and arcs have been inputed;
NODE *i; // current node
ARC *a; // current arc
ARC *a_stop;
BUCKET *b; // current bucket
long df;
_f_scale = (long) SCALE_DEFAULT;
_sentinel_node = _nodes + _n;
_sentinel_arc = _arcs + _m;
for ( i = _nodes; i != _sentinel_node; i ++ ) {
i->set_price( 0);
i->set_suspended( i->first());
i->set_q_next( _sentinel_node);
}
_sentinel_node->set_first( _sentinel_arc);
_sentinel_node->set_suspended( _sentinel_arc);
// saturate negative arcs, e.g. in the circulation problem case
for ( i = _nodes; i != _sentinel_node; i ++ ) {
for ( a = i->first(), a_stop = (i + 1)->suspended(); a != a_stop; a ++ ) {
if ( a->cost() < 0) {
if ( ( df = a->rez_capacity()) > 0) {
increase_flow( i, a->head(), a, df);
}
}
}
}
_dn = _n + 1;
if ( _no_zero_cycles == true) { // NO_ZERO_CYCLES
_dn = 2 * _dn;
}
for ( a = _arcs; a != _sentinel_arc; a ++ ) {
a->multiply_cost( _dn);
}
if ( _no_zero_cycles == true) { // NO_ZERO_CYCLES
for ( a = _arcs; a != _sentinel_arc; a ++ ) {
if ((a->cost() == 0) && (a->sister()->cost() == 0)) {
a->set_cost( 1);
a->sister()->set_cost( -1);
}
}
}
if ((double) _max_cost * (double) _dn > MAX_64) {
printf("Warning: Arc lengths too large, overflow possible\n");
}
_mmc = _max_cost * _dn;
_linf = (long) (_dn * ceil(_f_scale) + 2);
_buckets = (BUCKET*) calloc ( _linf, sizeof(BUCKET));
if ( _buckets == NULL )
err_end( ALLOCATION_FAULT);
_l_bucket = _buckets + _linf;
_dnode = new NODE; // used as reference;
for ( b = _buckets; b != _l_bucket; b ++ ) {
reset_bucket( b);
}
_epsilon = _mmc;
if ( _epsilon < 1) {
_epsilon = 1;
}
_price_min = -PRICE_MAX;
_cut_off_factor = CUT_OFF_COEF * pow( (double)_n, CUT_OFF_POWER);
_cut_off_factor = MAX( _cut_off_factor, CUT_OFF_MIN);
_n_ref = 0;
_flag_price = 0;
_dummy_node = &_d_node;
_excq_first = NULL;
//print_graph(); // debug;
}
void MCMF_CS2::up_node_scan( NODE *i)
{
NODE *j; // opposite node
ARC *a; // (i, j)
ARC *a_stop; // first arc from the next node
ARC *ra; // (j, i)
BUCKET *b_old; // old bucket contained j
BUCKET *b_new; // new bucket for j
long i_rank;
long j_rank; // ranks of nodes
long j_new_rank;
price_t rc; // reduced cost of (j, i)
price_t dr; // rank difference
_n_scan ++;
i_rank = i->rank();
// scanning arcs;
for ( a = i->first(), a_stop = (i + 1)->suspended(); a != a_stop; a ++ ) {
ra = a->sister();
if ( OPEN ( ra ) ) {
j = a->head();
j_rank = j->rank();
if ( j_rank > i_rank ) {
if ( ( rc = REDUCED_COST( j, i, ra ) ) < 0 ) {
j_new_rank = i_rank;
} else {
dr = rc / _epsilon;
j_new_rank = ( dr < _linf ) ? i_rank + (long)dr + 1 : _linf;
}
if ( j_rank > j_new_rank ) {
j->set_rank( j_new_rank);
j->set_current( ra);
if ( j_rank < _linf ) {
b_old = _buckets + j_rank;
REMOVE_FROM_BUCKET( j, b_old );
}
b_new = _buckets + j_new_rank;
insert_to_bucket( j, b_new );
}
}
}
}
i->dec_price( i_rank * _epsilon);
i->set_rank( -1);
}
void MCMF_CS2::price_update()
{
register NODE *i;
excess_t remain;
// total excess of unscanned nodes with positive excess;
BUCKET *b; // current bucket;
price_t dp; // amount to be subtracted from prices;
_n_update ++;
for ( i = _nodes; i != _sentinel_node; i ++ ) {
if ( i->excess() < 0 ) {
insert_to_bucket( i, _buckets );
i->set_rank( 0);
} else {
i->set_rank( _linf);
}
}
remain = _total_excess;
if ( remain < 0.5 ) return;
// scanning buckets, main loop;
for ( b = _buckets; b != _l_bucket; b ++ ) {
while ( nonempty_bucket( b) ) {
GET_FROM_BUCKET( i, b );
up_node_scan( i );
if ( i ->excess() > 0 ) {
remain -= ( i->excess());
if ( remain <= 0 ) break;
}
}
if ( remain <= 0 ) break;
}
if ( remain > 0.5 ) _flag_updt = 1;
// finishup
// changing prices for nodes which were not scanned during main loop;
dp = ( b - _buckets ) * _epsilon;
for ( i = _nodes; i != _sentinel_node; i ++ ) {
if ( i->rank() >= 0 ) {
if ( i->rank() < _linf ) {
REMOVE_FROM_BUCKET( i, ( _buckets + i->rank()) );
}
if ( i->price() > _price_min ) {
i->dec_price( dp);
}
}
}
}
int MCMF_CS2::relabel( NODE *i)
{
register ARC *a; // current arc from i
register ARC *a_stop; // first arc from the next node
register ARC *a_max; // arc which provides maximum price
register price_t p_max; // current maximal price
register price_t i_price; // price of node i
register price_t dp; // current arc partial residual cost
p_max = _price_min;
i_price = i->price();
a_max = NULL;
// 1/2 arcs are scanned;
for ( a = i->current() + 1, a_stop = (i + 1)->suspended(); a != a_stop; a ++ ) {
if ( OPEN(a) && ( (dp = (a->head()->price() - a->cost())) > p_max ) ) {
if ( i_price < dp ) {
i->set_current( a);
return ( 1);
}
p_max = dp;
a_max = a;
}
}
// 2/2 arcs are scanned;
for ( a = i->first(), a_stop = i->current() + 1; a != a_stop; a ++ ) {
if ( OPEN( a) && ( (dp = (a->head()->price() - a->cost())) > p_max ) ) {
if ( i_price < dp ) {
i->set_current( a);
return ( 1);
}
p_max = dp;
a_max = a;
}
}
// finishup
if ( p_max != _price_min ) {
i->set_price( p_max - _epsilon);
i->set_current( a_max);
}
else { // node can't be relabelled;
if ( i->suspended() == i->first() ) {
if ( i->excess() == 0 ) {
i->set_price( _price_min);
} else {
if ( _n_ref == 1 ) {
err_end( UNFEASIBLE );
} else {
err_end( PRICE_OFL );
}
}
} else { // node can't be relabelled because of suspended arcs;
_flag_price = 1;
}
}
_n_relabel ++;
_n_rel ++;
return ( 0);
}
void MCMF_CS2::discharge( NODE *i)
{
register ARC *a;// an arc from i
register NODE *j; // head of a
register long df; // amoumt of flow to be pushed through a
excess_t j_exc; // former excess of j
_n_discharge ++;
a = i->current();
j = a->head();
if ( !ADMISSIBLE( i, j, a ) ) {
relabel( i );
a = i->current();
j = a->head();
}
while ( 1 ) {
j_exc = j->excess();
if ( j_exc >= 0 ) {
df = MIN( i->excess(), a->rez_capacity() );
if ( j_exc == 0) _n_src++;
increase_flow( i, j, a, df ); // INCREASE_FLOW
_n_push ++;
if ( out_of_excess_q( j ) ) {
insert_to_excess_q( j );
}
}
else { // j_exc < 0;
df = MIN( i->excess(), a->rez_capacity() );
increase_flow( i, j, a, df ); // INCREASE_FLOW
_n_push ++;
if ( j->excess() >= 0 ) {
if ( j->excess() > 0 ) {
_n_src ++;
relabel( j );
insert_to_excess_q( j );
}
_total_excess += j_exc;
}
else {
_total_excess -= df;
}
}
if ( i->excess() <= 0) _n_src --;
if ( i->excess() <= 0 || _flag_price ) break;
relabel( i );
a = i->current();
j = a->head();
}
i->set_current( a);
}
int MCMF_CS2::price_in()
{
NODE *i; // current node
NODE *j;
ARC *a; // current arc from i
ARC *a_stop; // first arc from the next node
ARC *b; // arc to be exchanged with suspended
ARC *ra; // opposite to a
ARC *rb; // opposite to b
price_t rc; // reduced cost
int n_in_bad; // number of priced_in arcs with negative reduced cost
int bad_found; // if 1 we are at the second scan if 0 we are at the first scan
excess_t i_exc; // excess of i
excess_t df; // an amount to increase flow
bad_found = 0;
n_in_bad = 0;
restart:
for ( i = _nodes; i != _sentinel_node; i ++ ) {
for ( a = i->first() - 1, a_stop = i->suspended() - 1; a != a_stop; a -- ) {
rc = REDUCED_COST( i, a->head(), a );
if ( ( rc < 0) && ( a->rez_capacity() > 0) ) { // bad case;
if ( bad_found == 0 ) {
bad_found = 1;
update_cut_off();
goto restart;
}
df = a->rez_capacity();
increase_flow( i, a->head(), a, df );
ra = a->sister();
j = a->head();
i->dec_first();
b = i->first();
exchange( a, b );
if ( SUSPENDED( j, ra ) ) {
j->dec_first();
rb = j->first();
exchange( ra, rb );
}
n_in_bad ++;
}
else {
if ( ( rc < _cut_on ) && ( rc > -_cut_on ) ) {
i->dec_first();
b = i->first();
exchange( a, b );
}
}
}
}
if ( n_in_bad != 0 ) {
_n_bad_pricein ++;
// recalculating excess queue;
_total_excess = 0;
_n_src = 0;
reset_excess_q();
for ( i = _nodes; i != _sentinel_node; i ++ ) {
i->set_current( i->first());
i_exc = i->excess();
if ( i_exc > 0 ) { // i is a source;
_total_excess += i_exc;
_n_src ++;
insert_to_excess_q( i );
}
}
insert_to_excess_q( _dummy_node );
}
if ( _time_for_price_in == TIME_FOR_PRICE_IN2)
_time_for_price_in = TIME_FOR_PRICE_IN3;
if ( _time_for_price_in == TIME_FOR_PRICE_IN1)
_time_for_price_in = TIME_FOR_PRICE_IN2;
return ( n_in_bad);
}
void MCMF_CS2::refine()
{
NODE *i; // current node
excess_t i_exc; // excess of i
long np, nr, ns; // variables for additional print
int pr_in_int; // current number of updates between price_in
np = _n_push;
nr = _n_relabel;
ns = _n_scan;
_n_refine ++;
_n_ref ++;
_n_rel = 0;
pr_in_int = 0;
// initialize;
_total_excess = 0;
_n_src = 0;
reset_excess_q();
_time_for_price_in = TIME_FOR_PRICE_IN1;
for ( i = _nodes; i != _sentinel_node; i ++ ) {
i->set_current( i->first());
i_exc = i->excess();
if ( i_exc > 0 ) { // i is a source
_total_excess += i_exc;
_n_src++;
insert_to_excess_q( i );
}
}
if ( _total_excess <= 0 ) return;
// (2) main loop
while ( 1 ) {
if ( empty_excess_q() ) {
if ( _n_ref > PRICE_OUT_START ) {
pr_in_int = 0;
price_in();
}
if ( empty_excess_q() ) break;
}
REMOVE_FROM_EXCESS_Q( i );
// push all excess out of i
if ( i->excess() > 0 ) {
discharge( i );
if ( time_for_update() || _flag_price ) {
if ( i->excess() > 0 ) {
insert_to_excess_q( i );
}
if ( _flag_price && ( _n_ref > PRICE_OUT_START ) ) {
pr_in_int = 0;
price_in();
_flag_price = 0;
}
price_update();
while ( _flag_updt ) {
if ( _n_ref == 1 ) {
err_end( UNFEASIBLE );
} else {
_flag_updt = 0;
update_cut_off();
_n_bad_relabel ++;
pr_in_int = 0;
price_in();
price_update();
}
}
_n_rel = 0;
if ( _n_ref > PRICE_OUT_START && (pr_in_int ++ > _time_for_price_in) ) {
pr_in_int = 0;
price_in();
}
}
}
}
return;
}
int MCMF_CS2::price_refine()
{
NODE *i; // current node
NODE *j; // opposite node
NODE *ir; // nodes for passing over the negative cycle
NODE *is;
ARC *a; // arc (i,j)
ARC *a_stop; // first arc from the next node
ARC *ar;
long bmax; // number of farest nonempty bucket
long i_rank; // rank of node i
long j_rank; // rank of node j
long j_new_rank; // new rank of node j
BUCKET *b; // current bucket
BUCKET *b_old; // old and new buckets of current node
BUCKET *b_new;
price_t rc = 0; // reduced cost of a
price_t dr; // ranks difference
price_t dp;
int cc;
// return code: 1 - flow is epsilon optimal
// 0 - refine is needed
long df; // cycle capacity
int nnc; // number of negative cycles cancelled during one iteration
int snc; // total number of negative cycle cancelled
_n_prefine ++;
cc = 1;
snc = 0;
_snc_max = ( _n_ref >= START_CYCLE_CANCEL) ? MAX_CYCLES_CANCELLED : 0;
// (1) main loop
// while negative cycle is found or eps-optimal solution is constructed
while ( 1 ) {
nnc = 0;
for ( i = _nodes; i != _sentinel_node; i ++ ) {
i->set_rank( 0);
i->set_inp( WHITE);
i->set_current( i->first());
}
reset_stackq();
for ( i = _nodes; i != _sentinel_node; i ++ ) {
if ( i->inp() == BLACK ) continue;
i->set_b_next( NULL);
// deapth first search
while ( 1 ) {
i->set_inp( GREY);
// scanning arcs from node i starting from current
for ( a = i->current(), a_stop = (i + 1)->suspended(); a != a_stop; a ++) {
if ( OPEN( a ) ) {
j = a->head();
if ( REDUCED_COST ( i, j, a ) < 0 ) {
if ( j->inp() == WHITE ) { // fresh node - step forward
i->set_current( a);
j->set_b_next( i);
i = j;
a = j->current();
a_stop = (j+1)->suspended();
break;
}
if ( j->inp() == GREY ) { // cycle detected
cc = 0;
nnc ++;
i->set_current( a);
is = ir = i;
df = MAX_32;
while ( 1 ) {
ar = ir->current();
if ( ar->rez_capacity() <= df ) {
df = ar->rez_capacity();
is = ir;
}
if ( ir == j ) break;
ir = ir->b_next();
}
ir = i;
while ( 1 ) {
ar = ir->current();
increase_flow( ir, ar->head(), ar, df);
if ( ir == j ) break;
ir = ir->b_next();
}
if ( is != i ) {
for ( ir = i; ir != is; ir = ir->b_next() ) {
ir->set_inp( WHITE);
}
i = is;
a = is->current() + 1;
a_stop = (is+1)->suspended();
break;
}
}
}
// if j-color is BLACK - continue search from i
}
} // all arcs from i are scanned
if ( a == a_stop ) {
// step back
i->set_inp( BLACK);
_n_prscan1 ++;
j = i->b_next();
stackq_push( i );
if ( j == NULL ) break;
i = j;
i->inc_current();
}
} // end of deapth first search
} // all nodes are scanned
// () no negative cycle
// computing longest paths with eps-precision
snc += nnc;
if ( snc < _snc_max ) cc = 1;
if ( cc == 0 ) break;
bmax = 0;
while ( nonempty_stackq() ) {
_n_prscan2 ++;
STACKQ_POP( i );
i_rank = i->rank();
for ( a = i->first(), a_stop = (i + 1)->suspended(); a != a_stop; a ++) {
if ( OPEN( a ) ) {
j = a->head();
rc = REDUCED_COST( i, j, a );
if ( rc < 0 ) { // admissible arc;
dr = (price_t) (( - rc - 0.5 ) / _epsilon);
if (( j_rank = dr + i_rank ) < _linf ) {
if ( j_rank > j->rank() )
j->set_rank( j_rank);
}
}
}
} // all arcs from i are scanned
if ( i_rank > 0 ) {
if ( i_rank > bmax ) bmax = i_rank;
b = _buckets + i_rank;
insert_to_bucket( i, b );
}
} // end of while-cycle: all nodes are scanned - longest distancess are computed;
if ( bmax == 0 ) // preflow is eps-optimal;
{ break; }
for ( b = _buckets + bmax; b != _buckets; b -- ) {
i_rank = b - _buckets;
dp = i_rank * _epsilon;
while ( nonempty_bucket( b) ) {
GET_FROM_BUCKET( i, b );
_n_prscan ++;
for ( a = i->first(), a_stop = (i + 1)->suspended(); a != a_stop; a ++) {
if ( OPEN( a ) ) {
j = a->head();
j_rank = j->rank();
if ( j_rank < i_rank ) {
rc = REDUCED_COST( i, j, a );
if ( rc < 0 ) {
j_new_rank = i_rank;
} else {
dr = rc / _epsilon;
j_new_rank = ( dr < _linf ) ? i_rank - ( (long)dr + 1 ) : 0;
}