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ICBSSearch.cpp
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ICBSSearch.cpp
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#include "ICBSSearch.h"
#include <filesystem> // For exists, rename
#include <set>
#include <sstream>
#include <cstring> // For memcpy
#include <cstdlib> // For mkstemp, abs
#include <cstdio> // For fopen, fdopen
#include <spdlog/spdlog.h>
//#include <random> // For default_random_engine
//////////////////// HIGH LEVEL HEURISTICS ///////////////////////////
void ICBSSearch::remove_model_constraints(vector<vector<vector<GRBConstr>>>& Constraints, vector<vector<bool>>& CG, vector<bool>& nodeHasNontrivialEdges) {
for (int i = 0; i < num_of_agents; ++i) {
if (!nodeHasNontrivialEdges[i])
continue;
// Remove all edges connected to agent i
for (int other_agent = 0; other_agent < CG[i].size(); ++other_agent) {
if (CG[i][other_agent]) {
for (auto constraint : Constraints[i][other_agent]) { // No need to work with references - GrbConstr objects are just pointers - cheap to copy
// cerr << "Removing constraint for agents " << i << " and " << other_agent << endl;
mvc_model.remove(constraint);
}
CG[other_agent][i] = false;
// No need to clear the symmetric part of the matrix - we're not going to use it again
}
}
}
// mvc_model.reset(0);
}
void ICBSSearch::calc_mvc_mode_node_degrees(ICBSNode& curr, vector<int>& nodeDegrees) {
vector<vector<bool>> countedEdges(num_of_agents);
for (int i = 0; i < num_of_agents; i++)
countedEdges[i].resize(num_of_agents, false);
for (const auto& conf : curr.cardinalGoalConf)
{
const auto& [agent1, agent2, loc1, loc2, timestep] = *conf;
if (countedEdges[agent1][agent2] == false) {
nodeDegrees[agent1]++;
nodeDegrees[agent2]++;
countedEdges[agent1][agent2] = true;
countedEdges[agent2][agent1] = true;
}
}
for (const auto& conf : curr.cardinalConf)
{
const auto& [agent1, agent2, loc1, loc2, timestep] = *conf;
if (countedEdges[agent1][agent2] == false) {
nodeDegrees[agent1]++;
nodeDegrees[agent2]++;
countedEdges[agent1][agent2] = true;
countedEdges[agent2][agent1] = true;
}
}
}
// And increment h for trivial CG edges
void ICBSSearch::add_mvc_model_constraints_from_conflicts(vector<shared_ptr<Conflict>>& conflicts, vector<vector<bool>>& CG,
vector<int>& CgNodeDegrees, vector<vector<vector<GRBConstr>>>& Constraints,
int& num_of_nontrivial_CG_edges, vector<bool>& nodeHasNontrivialEdges,
int& h) {
for (const auto& conf : conflicts)
{
const auto& [agent1, agent2, loc1, loc2, timestep] = *conf;
bool alreadySeenConflictBetweenTheseTwo = CG[agent1][agent2]; // The two agents may have more than one cardinal conflict between them
if (!alreadySeenConflictBetweenTheseTwo) { // No point in adding the same mvc model constraint twice
if ((CgNodeDegrees[agent1] != 1) || (CgNodeDegrees[agent2] != 1)) {
GRBConstr constraint = mvc_model.addConstr(mvc_vars[agent1] + mvc_vars[agent2] >= 1);
Constraints[agent1][agent2].push_back(constraint);
Constraints[agent2][agent1].push_back(constraint);
num_of_nontrivial_CG_edges++;
nodeHasNontrivialEdges[agent1] = true;
nodeHasNontrivialEdges[agent2] = true;
}
else
h++;
CG[agent1][agent2] = true;
CG[agent2][agent1] = true;
}
}
}
void ICBSSearch::re_add_mvc_model_constraints_of_agent(vector<shared_ptr<Conflict>>& conflicts, int i,
vector<vector<vector<GRBConstr>>>& Constraints) {
for (const auto &conf: conflicts) {
const auto& [agent1, agent2, loc1, loc2, timestep] = *conf;
if ((agent1 == i) || (agent2 == i)) { // The edge involves our agent
GRBConstr constraint = mvc_model.addConstr(mvc_vars[agent1] + mvc_vars[agent2] >= 1);
Constraints[agent1][agent2].push_back(constraint);
Constraints[agent2][agent1].push_back(constraint);
}
}
}
// compute a heuristic estimate for the high-level node, and also choose a more promising conflict is one is found
// TODO: Separate the second part into a new function
#ifndef USE_GUROBI
int ICBSSearch::computeHeuristic(ICBSNode& curr)
{
// Build the cardinal conflict graph
vector<vector<bool>> CG(num_of_agents);
int num_of_CGnodes = 0, num_of_CGedges = 0;
for (int i = 0; i < num_of_agents; i++)
CG[i].resize(num_of_agents, false);
for (const auto& conf : curr.cardinalConf)
{
const auto& [agent1, agent2, loc1, loc2, timestep] = *conf;
if (!CG[agent1][agent2])
{
CG[agent1][agent2] = true;
CG[agent2][agent1] = true;
num_of_CGedges++;
}
}
if (num_of_CGedges < 2)
return num_of_CGedges;
// Compute #CG nodes that have edges
for (int i = 0; i < num_of_agents; i++)
{
for (int j = 0; j < num_of_agents; j++)
{
if (CG[i][j])
{
num_of_CGnodes++;
break;
}
}
}
if (num_of_CGedges == 2 && num_of_CGnodes == 4) // Two disjoint edges
return 2;
if (num_of_CGedges == 2 && num_of_CGnodes == 3) // Two edges that share a vertex
return 1;
// Minimum Vertex Cover
if (curr.parent == NULL) // root node of CBS tree
{
int i = 1;
while (!KVertexCover(CG, num_of_CGnodes, num_of_CGedges, i))
i++;
return i;
}
else if (KVertexCover(CG, num_of_CGnodes, num_of_CGedges, curr.parent->h_val - 1))
return curr.parent->h_val - 1;
else if (KVertexCover(CG, num_of_CGnodes, num_of_CGedges, curr.parent->h_val))
return curr.parent->h_val;
else
return curr.parent->h_val + 1;
}
#else
int ICBSSearch::computeHeuristic(ICBSNode& curr)
{
if (curr.cardinalGoalConf.empty() && curr.cardinalConf.empty())
return 0;
if (curr.cardinalGoalConf.size() + curr.cardinalConf.size() == 1)
return 1;
// Build the cardinal conflict graph
vector<vector<bool>> CG(num_of_agents); // Including trivial edges
vector<vector<vector<GRBConstr>>> Constraints(num_of_agents); // There can be both a cardinal goal conflict and
// a regular cardinal conflict between the same two agents,
// creating multiple different constraints on the pair of agents
vector<int> CgNodeDegrees(num_of_agents, 0); // Including trivial edges, multiple edges between edges only counted once
vector<bool> nodeHasNontrivialEdges(num_of_agents, false);
#ifndef GUROBI_WITH_GOAL_CONSTRAINTS
#else
vector<int> latestGoalConflictTimestep(num_of_agents, 0); // For an optimization of an easy case
vector<vector<int>> bestCostIncreaseForFirstAgent(num_of_agents);
#endif
int num_of_nontrivial_CG_edges = 0;
for (int i = 0; i < num_of_agents; i++) {
CG[i].resize(num_of_agents, false);
Constraints[i].resize(num_of_agents);
#ifndef GUROBI_WITH_GOAL_CONSTRAINTS
#else
bestCostIncreaseForFirstAgent[i].resize(num_of_agents, 0);
#endif
}
auto orig_conflict = curr.conflict;
int h = 0;
calc_mvc_mode_node_degrees(curr, CgNodeDegrees);
// Handle cardinal goal conflicts
#ifndef GUROBI_WITH_GOAL_CONSTRAINTS
// Treat cardinal goal conflicts as regular cardinal conflicts
add_mvc_model_constraints_from_conflicts(curr.cardinalGoalConf, CG, CgNodeDegrees, Constraints,
num_of_nontrivial_CG_edges,
nodeHasNontrivialEdges, h);
#else
for (const auto& conf: curr.cardinalGoalConf) {
// Find the latest timestep of a cardinal goal conflict between each two agents
const auto& [agent1, agent2, loc1, loc2, timestep] = *conf;
int cost_increase = timestep + 1 - ((*curr.all_paths)[agent2]->size() - 1); // conflict happens _after_ agent2 reaches its goal
// (because constraints are on the same time as the conflict,
// or earlier due to propagation)
if (cost_increase > bestCostIncreaseForFirstAgent[agent2][agent1])
bestCostIncreaseForFirstAgent[agent2][agent1] = cost_increase;
if (timestep > latestGoalConflictTimestep[agent2])
latestGoalConflictTimestep[agent2] = timestep;
}
for (const auto& conf: curr.cardinalGoalConf) {
const auto& [agent1, agent2, loc1, loc2, timestep] = *conf;
int cost_increase = bestCostIncreaseForFirstAgent[agent2][agent1];
bool alreadySeenConflictBetweenTheseTwo = CG[agent1][agent2]; // The two agents may have more than one cardinal goal conflict between them,
// but we're only adding the constraint for the latest one
if (!alreadySeenConflictBetweenTheseTwo) { // No point in adding the same constraint twice
if ((CgNodeDegrees[agent1] != 1) || (CgNodeDegrees[agent2] != 1)) {
GRBConstr constraint = mvc_model.addConstr(
mvc_vars[agent1] * cost_increase + mvc_vars[agent2] >= cost_increase);
Constraints[agent1][agent2].push_back(constraint);
Constraints[agent2][agent1].push_back(constraint);
num_of_nontrivial_CG_edges++;
nodeHasNontrivialEdges[agent1] = true;
nodeHasNontrivialEdges[agent2] = true;
}
else
h++;
CG[agent1][agent2] = true;
CG[agent2][agent1] = true;
}
}
#endif
// Handle f-cardinal, semi-f-cardinal, and cardinal conflicts
add_mvc_model_constraints_from_conflicts(curr.cardinalConf, CG, CgNodeDegrees, Constraints,
num_of_nontrivial_CG_edges,
nodeHasNontrivialEdges, h);
if (num_of_nontrivial_CG_edges == 0) // Then there are no f-cardinal conflicts to be found
return h;
if ((num_of_nontrivial_CG_edges == 2) && // Exactly three vertices and two edges - two edges that share a single vertex.
// (We already handled trivial edges earlier)
!preferFCardinals) // Otherwise we need to run the model
{
#ifndef GUROBI_WITH_GOAL_CONSTRAINTS
h += 1;
#else
// Find the middle agent
for (int i = 0; i < num_of_agents; i++) {
if (CgNodeDegrees[i] == 2) { // That's the middle agent
if (latestGoalConflictTimestep[i] >= (*curr.all_paths)[i]->size() - 1 + 1) // One of its conflicts is a goal conflict
h += 2; // Assign 1 to the agent that conflicts with the middle agent after the middle agent
// reached its goal, and 1 to one of the other agents the isn't at its goal when it
// conflicts with the other
else
h += 1;
break;
}
}
#endif
remove_model_constraints(Constraints, CG, nodeHasNontrivialEdges);
return h;
}
mvc_model.optimize();
// Get the size of the mvc
int nontrivial_mvc_size = mvc_model.getObjective().getValue();
h += nontrivial_mvc_size;
if (preferFCardinals && num_of_nontrivial_CG_edges != 0 // Look for an f-cardinal conflict among the cardinal conflicts,
// there's a chance of finding one (removing trivial edges always decreases the h by 1).
// && (eagerly_search_for_f_cardinals || curr.cardinalGoalConf.empty()) // Otherwise just stick with the at-least-semi-f-cardinal cardinal-goal conflict that we have
) {
// Find an edge that increases the cost without decreasing the size of the mvc -
// splitting on it will increase the F of one of the children, because that node's cost will increase (by 1, usually)
// and its h will stay the same. That's better than splitting on conflicts where the F of both children stays the same.
#ifndef GUROBI_WITH_GOAL_CONSTRAINTS
int best_h_decrease = 1; // When removing a vertex, the size of the mvc can only decrease by at most 1 (a lower decrease is better)
#else
// We could have a larger than 1 cost decrease from removing a vertex. For example, if 10 agents
// have a conflict with the same agent 3 timesteps after it reaches its goal, removing that agent would decrease
// the h by 4.
int best_h_decrease = numeric_limits<int>::max(); // A lower decrease is better
#endif
bool f_cardinal_found = false;
for (int i = 0; i < num_of_agents && !f_cardinal_found; ++i) {
if (nodeHasNontrivialEdges[i] == false) // Trivial edges always increase the h by exactly 1
continue;
// Remove all nontrivial edges connected to agent i
for (int other_agent = 0; other_agent < num_of_agents; ++other_agent) {
if (other_agent == i)
continue;
if (nodeHasNontrivialEdges[other_agent] == false) // Trivial edges always increase the h by exactly 1
continue;
for (auto constraint : Constraints[i][other_agent]) { // No need to work with references - GrbConstr objects are just pointers - cheap to copy
mvc_model.remove(constraint);
}
Constraints[i][other_agent].clear();
Constraints[other_agent][i].clear();
}
#ifndef GUROBI_WITH_GOAL_CONSTRAINTS
#else
// In theory, we would need to re-add the agent's cardinal-goal edges where it is the one that is at its goal
// with a 1-decrease on the coefficient of the other agent, but since we're not doing this if there are any
// cardinal goal conflicts, this isn't needed
// FIXME: WE ARE NOW DOING THIS, so do it
#endif
// Re-optimize
mvc_model.optimize();
int nontrivial_mvc_size_without_the_edges_of_the_node = mvc_model.getObjective().getValue();
int h_decrease = nontrivial_mvc_size - nontrivial_mvc_size_without_the_edges_of_the_node;
if (h_decrease < best_h_decrease) {
best_h_decrease = h_decrease;
}
if (h_decrease == 0) {
for (const auto& conf: curr.cardinalGoalConf) {
const auto&[agent1, agent2, loc1, loc2, timestep] = *conf;
if (agent1 == i) { // Our agent is the non-goal side - we found a full f-cardinal conflict!
// Can't improve that, skip adding the edges back - we're going to remove them all anyway.
f_cardinal_found = true;
curr.conflict = conf;
++f_cardinal_conflicts_found;
#ifndef GUROBI_WITH_GOAL_CONSTRAINTS
++h;
break;
#endif
}
}
if (curr.cardinalGoalConf.empty()) { // No cardinal-goal conflicts => in particular, the chosen conflict isn't cardinal-goal.
// Cardinal-goal conflicts are better than semi-f-cardinal conflicts
for (const auto& conf: curr.cardinalConf) {
const auto&[agent1, agent2, loc1, loc2, timestep] = *conf;
if ((agent1 == i) ||
(agent2 == i)) { // The edge involves our agent - we found a semi-f-cardinal conflict!
// Can't improve that, skip adding the edges back - we're going to remove them all anyway.
curr.conflict = conf; // Arbitrarily choose the agent's first semi-f-cardinal conflict
f_cardinal_found = true;
curr.branch_on_first_agent = (agent1 == i); // Branch on the this agent - adding a positive constraint on
// it might increase the cost of other agents besides the conflicting agent and
// make the conflict fully f-cardinal
++semi_f_cardinal_conflicts_found;
break;
}
}
}
}
// Add all the edges back (since the agent has a nontrivial edge, all its edges are nontrivial so we should add them all)
if (!f_cardinal_found) {
#ifndef GUROBI_WITH_GOAL_CONSTRAINTS
re_add_mvc_model_constraints_of_agent(curr.cardinalGoalConf, i, Constraints);
#else
re_add_mvc_model_goal_constraints_of_agent(curr.cardinalGoalConf, i, Constraints);
#endif
re_add_mvc_model_constraints_of_agent(curr.cardinalConf, i, Constraints);
}
}
if (f_cardinal_found) {
if (curr.conflict == orig_conflict)
spdlog::info("The already chosen conflict {}"
" will increase the F value of at least one of its children", *curr.conflict);
else
spdlog::info("Switched from conflict {} to conflict {}"
" - it will increase the F value of at least one of its children", *orig_conflict, *curr.conflict);
}
}
remove_model_constraints(Constraints, CG, nodeHasNontrivialEdges);
return h;
}
#endif
// return true if there exists a k-vertex cover
bool ICBSSearch::KVertexCover(const vector<vector<bool>>& CG, int num_of_CGnodes, int num_of_CGedges, int k)
{
if (num_of_CGedges == 0)
return true;
else if (num_of_CGedges > k * num_of_CGnodes - k)
return false;
vector<int> node(2);
bool flag = true;
for (int i = 0; i < num_of_agents - 1 && flag; i++) // to find an edge
{
for (int j = i + 1; j < num_of_agents && flag; j++)
{
if (CG[i][j])
{
node[0] = i;
node[1] = j;
flag = false;
}
}
}
for (int i = 0; i < 2; i++)
{
vector<vector<bool>> CG_copy(num_of_agents);
for (int j = 0; j < num_of_agents; j++)
{
CG_copy[j].resize(num_of_agents);
CG_copy.assign(CG.cbegin(), CG.cend());
}
int num_of_CGedges_copy = num_of_CGedges;
for (int j = 0; j < num_of_agents; j++)
{
if (CG_copy[node[i]][j])
{
CG_copy[node[i]][j] = false;
CG_copy[j][node[i]] = false;
num_of_CGedges_copy--;
}
}
if (KVertexCover(CG_copy, num_of_CGnodes - 1, num_of_CGedges_copy, k - 1))
return true;
}
return false;
}
//////////////////// CONSTRAINTS ///////////////////////////
// collect constraints from ancestors
void ICBSSearch::collectConstraints(ICBSNode* curr, std::list<pair<int, Constraint>> &constraints)
{
while (curr != nullptr)
{
for (const auto& con : curr->positive_constraints[curr->agent_id])
{
constraints.push_back(make_pair(curr->agent_id, con));
}
for (const auto& con : curr->negative_constraints[curr->agent_id])
{
constraints.push_back(make_pair(curr->agent_id, con));
}
curr = curr->parent;
}
// TODO: Use this function.
}
// build the constraint table for replanning agent <agent_id>,
// and find the two closest landmarks for agent <agent_id> that have the new constraint at time step <newConstraintTimestep> between them.
// TODO: Consider splitting into two functions
// update cons_table: cons_table[time_step, location].vertex or .edge = true iff they're a negative constraint for the agent
// update start and goal: the two landmarks for the agent such that its path between them violates the newly posted constraint (at <newConstraintTimestep>)
// return last goal constraint timestep - the time of the last constraint on an agent's goal
int ICBSSearch::buildConstraintTable(ICBSNode* curr, int agent_id, int newConstraintTimestep,
XytHolder<ConstraintState>& cons_table,
pair<int,int>& start, pair<int,int>& goal)
{
int lastGoalConsTimestep = -1;
// extract all constraints on agent_id
list < Constraint > constraints_negative;
while (curr != nullptr)
{
for (const auto& con: curr->negative_constraints[agent_id]) {
const auto& [loc1, loc2, constraint_timestep, positive_constraint] = con;
constraints_negative.push_back(con);
if (loc1 == goal.first && loc2 < 0 && lastGoalConsTimestep < constraint_timestep)
lastGoalConsTimestep = constraint_timestep;
}
for (int j = 0; j < num_of_agents ; ++j) {
if (j == agent_id) // For our agent, those are landmarks
{
for (const auto& con: curr->positive_constraints[j]) {
const auto& [loc1, loc2, constraint_timestep, positive_constraint] = con;
if (loc2 < 0) // vertex constraint
{
if (start.second < constraint_timestep && constraint_timestep < newConstraintTimestep) // This landmark is between (start.second, newConstraintTimestep)
{ // update start
start.first = loc1;
start.second = constraint_timestep;
} else if (newConstraintTimestep <= constraint_timestep && constraint_timestep < goal.second) // the landmark is between [newConstraintTimestep, goal.second)
{ // update goal
goal.first = loc1;
goal.second = constraint_timestep;
// If the landmark is at the same timestep as the new constraint, planning the new path will surely fail
}
} else // edge constraint, viewed as two landmarks on the from-vertex and the to-vertex
{
if (start.second < constraint_timestep && constraint_timestep < newConstraintTimestep) // the second landmark is between (start.second, newConstraintTimestep)
{ // update start
start.first = loc2;
start.second = constraint_timestep;
} else if (newConstraintTimestep <= constraint_timestep - 1 && constraint_timestep - 1 < goal.second) // the first landmark is between [newConstraintTimestep, goal.second)
{ // update goal
goal.first = loc1;
goal.second = constraint_timestep - 1;
}
}
// constraints_positive.push_back(con);
}
}
else { // for other agents, and specifically our agent, it is equivalent to a negative constraint
for (const auto& con: curr->positive_constraints[j]) {
const auto& [loc1, loc2, constraint_timestep, positive_constraint] = con;
if (loc1 == goal.first && loc2 < 0 && lastGoalConsTimestep < constraint_timestep) {
lastGoalConsTimestep = constraint_timestep;
}
constraints_negative.push_back(con);
}
}
}
curr = curr->parent;
}
if (lastGoalConsTimestep > goal.second) // because we only need to replan paths before goal.second
lastGoalConsTimestep = -1;
// Build the agent's negative constraints table
for (const auto& conflict : constraints_negative)
{
const auto& [loc1, loc2, constraint_timestep, positive_constraint] = conflict;
if (!positive_constraint) // So it's a negative constraint on this agent specifically
{
if (loc2 < 0) // vertex constraint
{
auto [found, state] = cons_table.get(loc1, constraint_timestep);
if (!found) {
state = new ConstraintState;
cons_table.set(loc1, constraint_timestep, state);
}
state->vertex = true;
}
else // edge constraint
{
for(int i = 0; i < MapLoader::valid_moves_t::WAIT_MOVE; i++)
{
if (loc2 - loc1 == moves_offset[i])
{
auto [found, state] = cons_table.get(loc2, constraint_timestep);
if (!found) {
state = new ConstraintState();
cons_table.set(loc2, constraint_timestep, state);
}
state->edge[i] = true;
break;
}
}
}
}
else if (loc2 < 0) // positive vertex constraint for another agent
{
auto [found, state] = cons_table.get(loc1, constraint_timestep);
if (!found) {
state = new ConstraintState;
cons_table.set(loc1, constraint_timestep, state);
}
state->vertex = true;
}
else // positive edge constraint for another agent
{
auto [found, state] = cons_table.get(loc1, constraint_timestep - 1);
if (!found) {
state = new ConstraintState;
cons_table.set(loc1, constraint_timestep - 1, state);
}
state->vertex = true;
auto [found2, state2] = cons_table.get(loc2, constraint_timestep);
if (!found) {
state2 = new ConstraintState;
cons_table.set(loc2, constraint_timestep, state2);
}
state2->vertex = true;
for (int i = 0; i < MapLoader::valid_moves_t::WAIT_MOVE; i++)
{
if (loc1 - loc2 == moves_offset[i]) {
auto [found_edge, state_edge] = cons_table.get(loc1, constraint_timestep);
if (!found) {
state_edge = new ConstraintState;
cons_table.set(loc1, constraint_timestep, state_edge);
}
state->edge[i] = true;
break;
}
}
}
}
return lastGoalConsTimestep;
}
// build conflict avoidance table
// update cat: Set cat[time_step][location].vertex or .edge[direction] to the number of other agents that plan to use it
void ICBSSearch::buildConflictAvoidanceTable(const ICBSNode &node, int exclude_agent, ConflictAvoidanceTable &cat)
{
if (node.makespan == 0)
return;
for (int ag = 0; ag < num_of_agents; ag++)
{
if (ag != exclude_agent &&
(*node.all_paths)[ag]->size() != 0 // Happens when computing the initial paths for the root node
)
{
addPathToConflictAvoidanceTable(*(*node.all_paths)[ag], cat, ag);
}
}
}
void ICBSSearch::addPathToConflictAvoidanceTable(Path &path, ConflictAvoidanceTable &cat, int agent_id) {
if (spdlog::default_logger()->level() <= spdlog::level::debug) {
ostringstream msg;
msg << "Adding the path (size " << path.size() - 1 << ") of agent " << agent_id << " to the CAT: ";
if (path.size() < 100)
{
int t = 0;
for ( ; t < path.size() - 1; t++)
msg << t << ": (" << path[t].location / num_map_cols << ","
<< path[t].location % num_map_cols << "), ";
msg << t << ": (" << path[t].location / num_map_cols << ","
<< path[t].location % num_map_cols << ")";
} else
msg << "(path too long to print)";
spdlog::debug(msg.str());
}
auto cat_start = std::clock();
auto wall_cat_start = std::chrono::system_clock::now();
int first_wait_at_goal_timestep = path.size();
for (int j = path.size() - 2; j >= 0 ; --j) {
if (path[j].location == path[j + 1].location)
--first_wait_at_goal_timestep;
else
break;
}
cat.add_wait_at_goal(first_wait_at_goal_timestep, path.back().location);
for (size_t timestep = 1; timestep < first_wait_at_goal_timestep; timestep++)
{
int to = path[timestep].location;
int from = path[timestep - 1].location;
cat.add_action(timestep, from, to);
}
cat_runtime += std::clock() - cat_start;
wall_cat_runtime += std::chrono::system_clock::now() - wall_cat_start;
}
void ICBSSearch::removePathFromConflictAvoidanceTable(Path &path, ConflictAvoidanceTable &cat, int agent_id) {
if (spdlog::default_logger()->level() <= spdlog::level::debug) {
ostringstream msg;
msg << "Removing the path (size " << path.size() - 1 << ") of agent " << agent_id << " from the CAT: ";
if (path.size() < 100) {
int t = 0;
for ( ; t < path.size() - 1; t++)
msg << t << ": (" << path[t].location / num_map_cols << ","
<< path[t].location % num_map_cols << "), ";
msg << t << ": (" << path[t].location / num_map_cols << ","
<< path[t].location % num_map_cols << ")";
} else
msg << "(path too long to print)";
spdlog::debug(msg.str());
}
auto cat_start = std::clock();
auto wall_cat_start = std::chrono::system_clock::now();
int first_wait_at_goal_timestep = path.size();
cat.remove_wait_at_goal(first_wait_at_goal_timestep, path.back().location);
for (size_t timestep = 1; timestep < path.size(); timestep++)
{
int to = path[timestep].location;
int from = path[timestep - 1].location;
cat.remove_action(timestep, from, to);
}
cat_runtime += std::clock() - cat_start;
wall_cat_runtime += std::chrono::system_clock::now() - wall_cat_start;
}
//////////////////// CONFLICTS ///////////////////////////
// copy conflicts from the parent node if the paths of both agents in the conflict remain unchanged from the parent
void ICBSSearch::copyConflictsFromParent(ICBSNode& curr)
{
auto hl_node_verification_start = std::clock();
auto wall_hl_node_verification_start = std::chrono::system_clock::now();
// Mark which paths remain unchanged from the parent node
vector<bool> unchanged(num_of_agents, true);
for (const auto & id_and_new_path : curr.new_paths) {
const auto& [agent_id, path] = id_and_new_path;
unchanged[agent_id] = false;
if (path.size() == 1 && path.back().location < 0) // Pathfinding was delayed for the agent -
// temporarily keep its conflicts so as not to
// give the node priority in FOCAL for work we haven't
// done yet (resolving them).
unchanged[agent_id] = true;
}
// Copy conflicts of agents both whose paths remain unchanged
copyConflicts(unchanged, curr.parent->cardinalGoalConf, curr.cardinalGoalConf);
copyConflicts(unchanged, curr.parent->cardinalConf, curr.cardinalConf);
copyConflicts(unchanged, curr.parent->semiCardinalGoalConf, curr.semiCardinalGoalConf);
copyConflicts(unchanged, curr.parent->semiCardinalConf, curr.semiCardinalConf);
copyConflicts(unchanged, curr.parent->nonCardinalConf, curr.nonCardinalConf);
copyConflicts(unchanged, curr.parent->unknownConf, curr.unknownConf);
hl_node_verification_runtime += std::clock() - hl_node_verification_start;
wall_hl_node_verification_runtime += std::chrono::system_clock::now() - wall_hl_node_verification_start;
}
void ICBSSearch::clearConflictsOfAgent(ICBSNode &curr, int ag)
{
auto hl_node_verification_start = std::clock();
auto wall_hl_node_verification_start = std::chrono::system_clock::now();
// Mark which paths remain unchanged from the parent node
bool unchanged[num_of_agents];
for (int j = 0; j < num_of_agents; ++j) {
unchanged[j] = true;
}
unchanged[ag] = false;
// Keep conflicts of agents both whose paths remain unchanged
clearConflictsOfAffectedAgents(unchanged, curr.cardinalGoalConf);
clearConflictsOfAffectedAgents(unchanged, curr.cardinalConf);
clearConflictsOfAffectedAgents(unchanged, curr.semiCardinalGoalConf);
clearConflictsOfAffectedAgents(unchanged, curr.semiCardinalConf);
clearConflictsOfAffectedAgents(unchanged, curr.nonCardinalConf);
clearConflictsOfAffectedAgents(unchanged, curr.unknownConf);
hl_node_verification_runtime += std::clock() - hl_node_verification_start;
wall_hl_node_verification_runtime += std::chrono::system_clock::now() - wall_hl_node_verification_start;
}
// copy conflicts from "from" to "to" if the paths of both agents remain unchanged
// according to the given array
void ICBSSearch::copyConflicts(const vector<bool>& unchanged,
const vector<std::shared_ptr<Conflict>>& from, vector<std::shared_ptr<Conflict>>& to)
{
for (const auto& conflict : from)
{
const auto& [agent1, agent2, loc1, loc2, timestep] = *conflict;
if (unchanged[agent1] && unchanged[agent2])
to.push_back(conflict);
}
}
// Of changed agents
void ICBSSearch::clearConflictsOfAffectedAgents(bool *unchanged,
vector<std::shared_ptr<Conflict>> &lst)
{
auto it = lst.begin();
while (it != lst.end()) {
const auto& [agent1, agent2, loc1, loc2, timestep] = **it;
if (!unchanged[agent1] || !unchanged[agent2])
it = lst.erase(it);
else
++it;
}
}
// find all conflict in the solution of the node
// assumes all_paths is populated correctly
void ICBSSearch::findConflicts(ICBSNode& curr)
{
auto hl_node_verification_start = std::clock();
auto wall_hl_node_verification_start = std::chrono::system_clock::now();
if (curr.parent != nullptr) // not root node
{
// detect conflicts that occur on the new planned paths
vector<bool> detectedTheConflictsOfThisAgent(num_of_agents, false);
for (const auto& pair : curr.new_paths)
{
const auto& [a1, path] = pair;
detectedTheConflictsOfThisAgent[a1] = true;
for (int a2 = 0; a2 < num_of_agents; a2++)
{
if (detectedTheConflictsOfThisAgent[a2])
continue;
findConflicts(curr, a1, a2);
}
}
}
else // root node
{ // detect conflicts among all paths
for(int a1 = 0; a1 < num_of_agents ; a1++)
{
for (int a2 = a1 + 1; a2 < num_of_agents; a2++)
{
findConflicts(curr, a1, a2);
}
}
}
hl_node_verification_runtime += std::clock() - hl_node_verification_start;
wall_hl_node_verification_runtime += std::chrono::system_clock::now() - wall_hl_node_verification_start;
}
void ICBSSearch::findConflicts(ICBSNode& curr, vector<int>& agents_with_new_paths) {
// detect conflicts that occur on the new planned paths
auto hl_node_verification_start = std::clock();
auto wall_hl_node_verification_start = std::chrono::system_clock::now();
vector<bool> detectedTheConflictsOfThisAgent(num_of_agents, false);
for (auto a1 : agents_with_new_paths) {
detectedTheConflictsOfThisAgent[a1] = true;
for (int a2 = 0; a2 < num_of_agents; a2++) {
if (detectedTheConflictsOfThisAgent[a2])
continue;
findConflicts(curr, a1, a2);
}
}
hl_node_verification_runtime += std::clock() - hl_node_verification_start;
wall_hl_node_verification_runtime += std::chrono::system_clock::now() - wall_hl_node_verification_start;
}
// find conflicts between paths of agents a1 and a2
void ICBSSearch::findConflicts(ICBSNode &curr, int a1, int a2)
{
Path& a1_path = *(*curr.all_paths)[a1];
Path& a2_path = *(*curr.all_paths)[a2];
size_t min_path_length = a1_path.size() < a2_path.size() ? a1_path.size() : a2_path.size();
for (int timestep = 0; timestep < min_path_length; timestep++)
{
int loc1 = a1_path[timestep].location;
int loc2 = a2_path[timestep].location;
if (loc1 == loc2)
{
curr.unknownConf.push_back(std::make_shared<Conflict>(a1, a2, loc1, -1, timestep));
}
else if (timestep < min_path_length - 1
&& loc1 == a2_path[timestep + 1].location
&& loc2 == a1_path[timestep + 1].location)
{
curr.unknownConf.push_back(std::make_shared<Conflict>(a1, a2, loc1, loc2, timestep + 1)); // edge conflict
}
}
if (a1_path.size() != a2_path.size()) // check whether there are conflicts that occur after one agent reaches its goal
{
int agent_with_shorter_path = a1_path.size() < a2_path.size() ? a1 : a2;
int agent_with_longer_path = a1_path.size() < a2_path.size() ? a2 : a1;
Path& shorter_path = *(*curr.all_paths)[agent_with_shorter_path];
Path& longer_path = *(*curr.all_paths)[agent_with_longer_path];
int loc1 = shorter_path.back().location;
for (int timestep = (int)min_path_length; timestep < longer_path.size(); timestep++)
{
int loc2 = longer_path[timestep].location;
if (loc1 == loc2)
{ // It's at least a semi cardinal conflict
curr.unknownConf.push_back(std::make_shared<Conflict>(
agent_with_longer_path, agent_with_shorter_path, loc1, -1, timestep));
}
}
}
}
// Classify conflicts into the different cardinality classes and populate the node's conflict lists with them.
// If a CBS heuristic isn't used, return the first (f-)cardinal conflict that was found immediately, without finishing
// the classification of conflicts.
// The CAT is only used if LPA* is used to build the MDDs for checking if conflicts are cardinal
void ICBSSearch::classifyConflicts(ICBSNode &node, ConflictAvoidanceTable* cat /* = nullptr*/)
{
if (node.cardinalGoalConf.empty() &&
node.cardinalConf.empty() && node.semiCardinalGoalConf.empty() &&
node.semiCardinalConf.empty() && node.nonCardinalConf.empty() && node.unknownConf.empty())
return; // No conflict
// Classify all conflicts in unknownConf
while (!node.unknownConf.empty())
{
if (std::clock() > start + time_limit * CLOCKS_PER_SEC) // timeout
{
spdlog::warn("Timed out classifying conflicts!");
break;
}
std::shared_ptr<Conflict> con = node.unknownConf.back();
const auto& [agent1, agent2, loc1, loc2, timestep] = *con;
Path & a1_path = *(*node.all_paths)[agent1];
Path & a2_path = *(*node.all_paths)[agent2];
bool cardinal1, cardinal2;
bool goal_conflict1 = false;
bool goal_conflict2 = false;
if (loc2 >= 0) // Edge conflict (no need to check if it happens after one agent has already reached its goal)
{
bool success = buildMDD(node, agent1, timestep, 0, cat); // Build an MDD for the agent's current cost, unless we already know if it's narrow at <timestep>
if (!success)
break;
success = buildMDD(node, agent2, timestep, 0, cat);
if (!success)
break;
// TODO: If we can already tell the conflict is at most semi-g-cardinal and won't factor into the heuristic,
// Skip building the other MDD and push the conflict into a semi-g-cardinal-or-non-cardinal vector.
// We might never need the other agent's MDD.
success = buildMDD(node, agent1, timestep - 1, 0, cat); // Build an MDD for the agent's current cost, unless we already know if it's narrow at <timestep - 1>
if (!success)
break;
success = buildMDD(node, agent2, timestep - 1, 0, cat);
if (!success)
break;
cardinal1 = a1_path[timestep].single && a1_path[timestep - 1].single;
cardinal2 = a2_path[timestep].single && a2_path[timestep - 1].single;
}
else // vertex conflict
{
if (timestep >= a1_path.size()) {
goal_conflict1 = true;
cardinal1 = true;
}
else
{
bool success = buildMDD(node, agent1, timestep, 0, cat);
if (!success)
break;
cardinal1 = a1_path[timestep].single;
// TODO: If we can already tell the conflict is at most semi-g-cardinal and won't factor into the heuristic,
// Skip building the other MDD and push the conflict into a semi-g-cardinal-or-non-cardinal vector.
}
if (timestep >= a2_path.size()) {
goal_conflict2 = true;
cardinal2 = true;
}
else
{
bool success = buildMDD(node, agent2, timestep, 0, cat);
if (!success)
break;
cardinal2 = a2_path[timestep].single;
}
}
if (cardinal1 && cardinal2)
{
if (goal_conflict1 || goal_conflict2) {
if (goal_conflict2) {
node.cardinalGoalConf.push_back(con);
++cardinal_goal_conflicts_found;
} else { // then goal_conflict1 - make sure the agent with the lower f-increase is first
if (loc2 < 0) {
node.cardinalGoalConf.push_back(
std::make_shared<Conflict>(agent2, agent1, loc1, -1, timestep));
++cardinal_goal_conflicts_found;
}
else {
node.cardinalGoalConf.push_back(
std::make_shared<Conflict>(agent2, agent1, loc2, loc1, timestep));
++cardinal_goal_conflicts_found;
}
}
if (HL_heuristic == highlevel_heuristic::NONE && preferGoalConflicts) // Found a cardinal goal conflict and they're not used to
// compute heuristics. Return it immediately.
// FIXME: Don't we need to find all of them so we can choose the one with the highest cost increase for the second agent?
{
conflictType = conflict_type::CARDINAL_GOAL;
node.unknownConf.pop_back(); // Only pop it from unknown after we put it in the correct bin
++cardinal_goal_conflicts_found;
return;
}
}
else {
node.cardinalConf.push_back(con);
++cardinal_conflicts_found;
if (HL_heuristic == highlevel_heuristic::NONE && !preferGoalConflicts) // Found a goal conflict and they're not used to complete heuristics. Return it immediately.
{
conflictType = conflict_type::CARDINAL_GOAL;
node.unknownConf.pop_back(); // Only pop it from unknown after we put it in the correct bin
++cardinal_goal_conflicts_found;
return;
}
}
if (HL_heuristic == highlevel_heuristic::NONE) // Found a cardinal conflict and they're not used to complete heuristics. Return it immediately.
{
if (goal_conflict1 || goal_conflict2) {
conflictType = conflict_type::CARDINAL_GOAL;
}
else
conflictType = conflict_type::CARDINAL;
node.unknownConf.pop_back(); // Only pop it from unknown after we put it in the correct bin
++cardinal_conflicts_found;
return;
}
}
else if (cardinal2)
{
if (goal_conflict2) {
node.semiCardinalGoalConf.push_back(con);
++semi_cardinal_goal_conflicts_found;
}
else {
node.semiCardinalConf.push_back(con);
++semi_cardinal_conflicts_found;
}
}
else if (cardinal1) // Make sure the non-cardinal agent is first
{
if (goal_conflict1) {
if (loc2 >= 0) {
node.semiCardinalGoalConf.push_back(
std::make_shared<Conflict>(agent2, agent1, loc2, loc1, timestep));
++semi_cardinal_goal_conflicts_found;
}
else {