private function run_discussion_order_once($cflt, $plist)
{
$m = new MinCostMaxFlow();
$m->add_progressf(array($this, "mcmf_progress"));
$this->set_progress("Preparing assignment optimizer");
// paper nodes
// set p->po edge cost so low that traversing that edge will
// definitely lower total cost; all positive costs are <=
// count($this->pcm), so this edge should have cost:
$pocost = -(count($this->pcm) + 1);
$this->mcmf_max_cost = $pocost * count($plist) * 0.75;
$m->add_node(".s", "source");
$m->add_edge(".source", ".s", 1, 0);
foreach ($plist as $i => $pids) {
$m->add_node("p{$i}", "p");
$m->add_node("po{$i}", "po");
$m->add_edge(".s", "p{$i}", 1, 0);
$m->add_edge("p{$i}", "po{$i}", 1, $pocost);
$m->add_edge("po{$i}", ".sink", 1, 0);
}
// conflict edges
$plist2 = $plist;
// need copy for different iteration ptr
foreach ($plist as $i => $pid1) {
foreach ($plist2 as $j => $pid2) {
if ($i != $j) {
$pid1 = is_array($pid1) ? $pid1[count($pid1) - 1] : $pid1;
$pid2 = is_array($pid2) ? $pid2[0] : $pid2;
// cost of edge is number of different conflicts
$cost = count($cflt[$pid1] + $cflt[$pid2]) - count(array_intersect($cflt[$pid1], $cflt[$pid2]));
$m->add_edge("po{$i}", "p{$j}", 1, $cost);
}
}
}
// run MCMF
$this->mcmf = $m;
$m->shuffle();
$m->run();
// extract next roots
$roots = array_keys($plist);
$result = array();
while (count($roots)) {
$source = ".source";
if (count($roots) !== count($plist)) {
$source = "p" . $roots[mt_rand(0, count($roots) - 1)];
}
$pgroup = $igroup = array();
foreach ($m->topological_sort($source, "p") as $v) {
$pidx = (int) substr($v->name, 1);
$igroup[] = $pidx;
if (is_array($plist[$pidx])) {
$pgroup = array_merge($pgroup, $plist[$pidx]);
} else {
$pgroup[] = $plist[$pidx];
}
}
$result[] = $pgroup;
$roots = array_values(array_diff($roots, $igroup));
}
// done
$m->clear();
// break circular refs
$this->mcmf = null;
$this->profile["maxflow"] += $m->maxflow_end_at - $m->maxflow_start_at;
if ($m->mincost_start_at) {
$this->profile["mincost"] += $m->mincost_end_at - $m->mincost_start_at;
}
return $result;
}
srand($seed);
// the shuffle() uses this seed
$m->shuffle();
$m->run();
$assignments[mcmf_assignment_text($m)] = true;
}
$assignments = array_keys($assignments);
sort($assignments);
xassert_eqq(count($assignments), 2);
xassert_eqq($assignments[0], "u0 p0\nu1 p1\nu2 p2\n");
xassert_eqq($assignments[1], "u0 p1\nu1 p0\nu2 p2\n");
fwrite(STDERR, "- Phase 3 complete.\n");
// (4) all zero preferences => all possible results; this uses push-relabel
$m = new MinCostMaxFlow();
foreach (array("u0", "u1", "u2") as $x) {
$m->add_node($x, "u");
$m->add_edge(".source", $x, 1);
}
foreach (array("p0", "p1", "p2") as $x) {
$m->add_node($x, "p");
$m->add_edge($x, ".sink", 1);
}
foreach (array("u0", "u1", "u2") as $x) {
foreach (array("p0", "p1", "p2") as $y) {
$m->add_edge($x, $y, 1);
}
}
$assignments = array();
foreach (range(100, 921384, 1247) as $seed) {
$m->reset();
srand($seed);