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Added a shortest-path algorithm between two nodes and removed the hardwired KEMT-specific path. Also tidied up some bugs in the gate handling code

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This commit is contained in:
daveluff 2003-02-24 19:03:15 +00:00
parent c07f22ea16
commit e805a4188c
2 changed files with 226 additions and 87 deletions

263
src/ATC/ground.cxx
View file

@ -29,10 +29,25 @@
#include STL_FSTREAM
#include "ground.hxx"
#include "ATCutils.hxx"
SG_USING_STD(ifstream);
SG_USING_STD(cout);
node::node() {
}
node::~node() {
for(unsigned int i=0; i < arcs.size(); ++i) {
delete arcs[i];
}
}
// Make sure that a_path.cost += distance is safe from the moment it's created.
a_path::a_path() {
cost = 0;
}
FGGround::FGGround() {
display = false;
networkLoadOK = false;
@ -63,11 +78,17 @@ void FGGround::ParseRwyExits(node* np, char* es) {
// Return true if successfull.
// TODO - currently the file is assumed to reside in the base/ATC directory.
// This might change to something more thought out in the future.
// NOTE - currently it is assumed that all nodes are loaded before any arcs.
// It won't work ATM if this doesn't hold true.
bool FGGround::LoadNetwork() {
node* np;
arc* ap;
Gate* gp;
int gateCount = 0; // This is used to allocate gateID's from zero upwards
// This may well change in the future - probably to reading in the real-world
// gate numbers from file.
ifstream fin;
SGPath path = globals->get_fg_root();
//string taxiPath = "ATC/" + ident + ".taxi";
@ -175,6 +196,8 @@ bool FGGround::LoadNetwork() {
} // we shouldn't need the 0x0A but it makes a nice safely in case someone leaves off the "
}
fin.setf(ios::skipws);
ap->distance = (int)dclGetHorizontalSeparation(network[ap->n1]->pos, network[ap->n2]->pos);
cout << "Distance = " << ap->distance << '\n';
network[ap->n1]->arcs.push_back(ap);
network[ap->n2]->arcs.push_back(ap);
} else if(!strcmp(buf, "G")) {
@ -203,7 +226,11 @@ bool FGGround::LoadNetwork() {
} // we shouldn't need the 0x0A but it makes a nice safely in case someone leaves off the "
}
fin.setf(ios::skipws);
gp->id = gateCount; // Warning - this will likely change in the future.
gp->used = false;
network.push_back(gp);
gates[gateCount] = gp;
gateCount++;
} else {
// Something has gone seriously pear-shaped
cout << "********* ERROR - unknown ground network element type... aborting read of " << path.c_str() << '\n';
@ -241,116 +268,199 @@ void FGGround::Update() {
// Next we need to decide where its going.
}
// FIXME - at the moment this assumes there is at least one gate and crashes if none
// FIXME - In fact, at the moment this routine doesn't work at all and hence is munged to always return Gate 1 !!!!
// Return a random gate ID of an unused gate.
// Two error values may be returned and must be checked for by the calling function:
// -2 signifies that no gates exist at this airport.
// -1 signifies that all gates are currently full.
int FGGround::GetRandomGateID() {
//cout << "GetRandomGateID called" << endl;
return(1);
// Check that this airport actually has some gates!!
if(!gates.size()) {
return(-2);
}
gate_vec_type gateVec;
//gate_vec_iterator gateVecItr;
int num = 0;
int thenum;
int ID;
gatesItr = gates.begin();
while(gatesItr != gates.end()) {
if(gatesItr->second.used == false) {
if((gatesItr->second)->used == false) {
gateVec.push_back(gatesItr->second);
num++;
}
++gatesItr;
}
// Check that there are some unused gates!
if(!gateVec.size()) {
return(-1);
}
// Randomly select one from the list
sg_srandom_time();
thenum = (int)(sg_random() * gateVec.size());
ID = gateVec[thenum].id;
//cout << "Returning gate ID " << ID << " from GetRandomGateID" << endl;
ID = gateVec[thenum]->id;
return(ID);
}
// Return a pointer to a gate node based on the gate ID
Gate* FGGround::GetGateNode(int gateID) {
//TODO - ought to add some sanity checking here - ie does a gate of this ID exist?!
return(&(gates[gateID]));
// Return a pointer to an unused gate node
Gate* FGGround::GetGateNode() {
int id = GetRandomGateID();
if(id < 0) {
return(NULL);
} else {
return(gates[id]);
}
}
// Get a path from a point on a runway to a gate
// TODO !!
// Get a path from a node to another node
// Eventually we will need complex algorithms for this taking other traffic,
// shortest path and suitable paths into accout. For now we're going to hardwire for KEMT!!!!
// shortest path and suitable paths into accout.
// For now we'll just call the shortest path algorithm.
ground_network_path_type FGGround::GetPath(node* A, node* B) {
ground_network_path_type path;
//arc_array_iterator arcItr;
//bool found;
return(GetShortestPath(A, B));
};
// VERY HARDWIRED - this hardwires a path from the far end of R01 to Gate 1.
// In fact in real life the area between R01/19 and Taxiway Alpha at KEMT is tarmaced and planes
// are supposed to exit the rwy asap.
// OK - for now very hardwire this for testing
path.push_back(network[1]);
path.push_back(network[1]->arcs[1]); // ONLY BECAUSE WE KNOW THIS IS THE ONE !!!!!
path.push_back(network[3]);
path.push_back(network[3]->arcs[1]);
path.push_back(network[5]);
path.push_back(network[5]->arcs[0]);
path.push_back(network[4]);
path.push_back(network[4]->arcs[2]);
path.push_back(network[6]);
path.push_back(network[6]->arcs[2]);
path.push_back(network[7]); // THE GATE!! Note that for now we're not even looking at the requested exit and gate passed in !!!!!
#if 0
// In this hardwired scheme there are two possibilities - taxiing from rwy to gate or gate to rwy.
if(B->type == GATE) {
//return an inward path
path.push_back(A);
// In this hardwired scheme we know A is a rwy exit and should have one taxiway arc only
// THIS WILL NOT HOLD TRUE IN THE GENERAL CASE
arcItr = A->arcs.begin();
found = false;
while(arcItr != A->arcs.end()) {
if(arcItr->type == TAXIWAY) {
path.push_back(&(*arcItr));
found = true;
break;
// A shortest path algorithm from memory (ie. I can't find the bl&*dy book again!)
// I'm sure there must be enchancements that we can make to this, such as biasing the
// order in which the nodes are searched out from in favour of those geographically
// closer to the destination.
// Note that we are working with the master set of nodes and arcs so we mustn't change
// or delete them - we only delete the paths that we create during the algorithm.
ground_network_path_type FGGround::GetShortestPath(node* A, node* B) {
a_path* pathPtr;
shortest_path_map_type pathMap;
node_array_type nodesLeft;
// Debugging check
int pathsCreated = 0;
// Initialise the algorithm
nodesLeft.push_back(A);
pathPtr = new a_path;
pathsCreated++;
pathPtr->path.push_back(A);
pathPtr->cost = 0;
pathMap[A->nodeID] = pathPtr;
bool solution_found = false; // Flag to indicate that at least one candidate path has been found
int solution_cost = -1; // Cost of current best cost solution. -1 indicates no solution found yet.
a_path solution_path;
node* nPtr; // nPtr is used to point to the node we are currently working with
while(nodesLeft.size()) {
//cout << "\n*****nodesLeft*****\n";
//for(unsigned int i=0; i<nodesLeft.size(); ++i) {
//cout << nodesLeft[i]->nodeID << '\n';
//}
//cout << "*******************\n\n";
nPtr = *nodesLeft.begin(); // Thought - definate optimization possibilities here in the choice of which nodes we process first.
nodesLeft.erase(nodesLeft.begin());
//cout << "Walking out from node " << nPtr->nodeID << '\n';
for(unsigned int i=0; i<nPtr->arcs.size(); ++i) {
//cout << "ARC TO " << ((nPtr->arcs[i]->n1 == nPtr->nodeID) ? nPtr->arcs[i]->n2 : nPtr->arcs[i]->n1) << '\n';
}
if((solution_found) && (solution_cost <= pathMap[nPtr->nodeID]->cost)) {
// Do nothing - we've already found a solution and this partial path is already more expensive
} else {
// This path could still be better than the current solution - check it out
for(unsigned int i=0; i<(nPtr->arcs.size()); i++) {
// Map the new path against the end node, ie. *not* the one we just started with.
unsigned int end_nodeID = ((nPtr->arcs[i]->n1 == nPtr->nodeID) ? nPtr->arcs[i]->n2 : nPtr->arcs[i]->n1);
//cout << "end_nodeID = " << end_nodeID << '\n';
//cout << "pathMap size is " << pathMap.size() << '\n';
if(end_nodeID == nPtr->nodeID) {
//cout << "Circular arc!\n";
// Then its a circular arc - don't bother!!
//nPtr->arcs.erase(nPtr->arcs.begin() + i);
} else {
// see if the end node is already in the map or not
if(pathMap.find(end_nodeID) == pathMap.end()) {
//cout << "Not in the map" << endl;;
// Not in the map - easy!
pathPtr = new a_path;
pathsCreated++;
*pathPtr = *pathMap[nPtr->nodeID]; // *copy* the path
pathPtr->path.push_back(nPtr->arcs[i]);
pathPtr->path.push_back(network[end_nodeID]);
pathPtr->cost += nPtr->arcs[i]->distance;
pathMap[end_nodeID] = pathPtr;
nodesLeft.push_back(network[end_nodeID]); // By definition this can't be in the list already, or
// it would also have been in the map and hence OR'd with this one.
if(end_nodeID == B->nodeID) {
//cout << "Solution found!!!" << endl;
// Since this node wasn't in the map this is by definition the first solution
solution_cost = pathPtr->cost;
solution_path = *pathPtr;
solution_found = true;
}
} else {
//cout << "Already in the map" << endl;
// In the map - not so easy - need to get rid of an arc from the higher cost one.
//cout << "Current cost of node " << end_nodeID << " is " << pathMap[end_nodeID]->cost << endl;
int newCost = pathMap[nPtr->nodeID]->cost + nPtr->arcs[i]->distance;
//cout << "New cost is of node " << nPtr->nodeID << " is " << newCost << endl;
if(newCost >= pathMap[end_nodeID]->cost) {
// No need to do anything.
//cout << "Not doing anything!" << endl;
} else {
delete pathMap[end_nodeID];
pathsCreated--;
pathPtr = new a_path;
pathsCreated++;
*pathPtr = *pathMap[nPtr->nodeID]; // *copy* the path
pathPtr->path.push_back(nPtr->arcs[i]);
pathPtr->path.push_back(network[end_nodeID]);
pathPtr->cost += nPtr->arcs[i]->distance;
pathMap[end_nodeID] = pathPtr;
// We need to add this node to the list-to-do again to force a recalculation
// onwards from this node with the new lower cost to node cost.
nodesLeft.push_back(network[end_nodeID]);
if(end_nodeID == B->nodeID) {
//cout << "Solution found!!!" << endl;
// Need to check if there is a previous better solution
if((solution_cost < 0) || (pathPtr->cost < solution_cost)) {
solution_cost = pathPtr->cost;
solution_path = *pathPtr;
solution_found = true;
}
}
}
}
}
}
}
if(found == false) {
//cout << "AI/ATC SUBSYSTEM ERROR - no taxiway from runway exit in airport.cxx" << endl;
}
// Then push back the start of taxiway node
// Then push back the taxiway arc
arcItr = A->arcs.begin();
found = false;
while(arcItr != A->arcs.end()) {
if(arcItr->type == TAXIWAY) { // FIXME - OOPS - two taxiways go off this node
// How are we going to differentiate, apart from one called Alpha.
// I suppose eventually the traversal algorithms will select.
path.push_back(&(*arcItr));
found = true;
break;
}
}
if(found == false) {
//cout << "AI/ATC SUBSYSTEM ERROR - no taxiway from runway exit in airport.cxx" << endl;
}
// Then push back the junction node
// Planes always face one way in the parking, so depending on which parking exit we have either take it or push back another taxiway node
// Repeat if necessary
// Then push back the gate B
path.push_back(B);
} else {
//return an outward path
}
// WARNING TODO FIXME - this is VERY FRAGILE - eg taxi to apron!!! but should be enough to
// see an AI plane physically taxi.
#endif // 0
// delete all the paths before returning
shortest_path_map_iterator spItr = pathMap.begin();
while(spItr != pathMap.end()) {
if(spItr->second != NULL) {
delete spItr->second;
--pathsCreated;
}
++spItr;
}
//cout << "pathsCreated = " << pathsCreated << '\n';
if(pathsCreated > 0) {
SG_LOG(SG_GENERAL, SG_ALERT, "WARNING - Possible memory leak in FGGround::GetShortestPath\n\
Please report to flightgear-devel@flightgear.org\n");
}
//cout << (solution_found ? "Result: solution found\n" : "Result: no solution found\n");
return(solution_path.path); // TODO - we really ought to have a fallback position incase a solution isn't found.
}
return(path);
};
// Randomly or otherwise populate some of the gates with parked planes
@ -403,3 +513,4 @@ void FGGround::AssignGate(ground_rec &g) {
// In the long run the logic of which gate or area to send the plane to could be somewhat non-trivial.
}
#endif //0

44
src/ATC/ground.hxx
View file

@ -95,6 +95,9 @@ typedef arc_array_type::iterator arc_array_iterator;
typedef arc_array_type::const_iterator arc_array_const_iterator;
struct node : public ground_network_element {
node();
~node();
unsigned int nodeID; //each node in an airport needs a unique ID number - this is ZERO-BASED to match array position
Point3D pos;
Point3D orthoPos;
@ -119,12 +122,12 @@ struct Gate : public node {
double heading; // The direction the parked-up plane should point in degrees
};
typedef vector < Gate > gate_vec_type;
typedef vector < Gate* > gate_vec_type;
typedef gate_vec_type::iterator gate_vec_iterator;
typedef gate_vec_type::const_iterator gate_vec_const_iterator;
// A map of gate vs. the logical (internal FGFS) gate ID
typedef map < int, Gate > gate_map_type;
typedef map < int, Gate* > gate_map_type;
typedef gate_map_type::iterator gate_map_iterator;
typedef gate_map_type::const_iterator gate_map_const_iterator;
@ -154,6 +157,25 @@ typedef ground_network_path_type::const_iterator ground_network_path_const_itera
//////////////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////
//
// Stuff for the shortest-path algorithms
struct a_path {
a_path();
ground_network_path_type path;
int cost;
};
// Paths mapped by nodeID reached so-far
typedef map < unsigned int, a_path* > shortest_path_map_type;
typedef shortest_path_map_type::iterator shortest_path_map_iterator;
// Nodes mapped by their ID
//typedef map < unsigned int, node* > node_map_type;
//typedef node_map_type::iterator node_map_iterator;
////////////////////////////////////////////////
// Planes active within the ground network.
// somewhere in the ATC/AI system we are going to have defined something like
// typedef struct plane_rec
@ -217,12 +239,8 @@ public:
// Return a suitable gate (maybe this should be a list of suitable gates so the plane or controller can choose the closest one)
void ReturnGate(Gate &gate, GateType type);
//The following two functions have been made public for now but may go private with a higher level accessor at some point
// Return the internal ID of a random, suitable, unused gate
// For now we are simply implementing as any random unused gate
int GetRandomGateID();
// Return a pointer to a node based on the gate ID
Gate* GetGateNode(int gateID);
// Return a pointer to an unused gate
Gate* GetGateNode();
// Runway stuff - this might change in the future.
// Get a list of exits from a given runway
@ -284,6 +302,16 @@ private:
// Parse a runway exit string and push the supplied node pointer onto the runway exit list
void ParseRwyExits(node* np, char* es);
// Return a random gate ID of an unused gate.
// Two error values may be returned and must be checked for by the calling function:
// -2 signifies that no gates exist at this airport.
// -1 signifies that all gates are currently full.
// TODO - modify to return a suitable gate based on aircraft size/weight.
int GetRandomGateID();
// A shortest path algorithm sort of from memory (I can't find the bl&*dy book again!)
ground_network_path_type GetShortestPath(node* A, node* B);
};
#endif // _FG_GROUND_HXX