Cost Factor in Shortest Path
Hi,
I need a little help.
I am performing routing on geodatic data (i.e., locations with Lat/Long).
I think the AStar shortest path algorithms are finding the shortest path on the basis of distance betwwen two nodes.
I am not quite sure whether they are taking care of the cost column in the link table.
for eg., say A-B-C and A-D-C are two alternative routes from A to C .
such that A-B-C is the shortest path on the basis of geodatic distance between the locations A an C.
But may be the cost-wise A-D-C would have been a shorter path.
So, which path will the algo return?
Also I do not want to implement AStarCostFunction class and provide a distance function.
Please help me out.
Regards.
Hi,
Any/all cost-based analysis in the network data model is done using the cost column. If the cost column contains geodetic distances then that is what will be used.
Hope this helps,
Dan
Similar Messages
-
Computing of the shortest path using a custom cost function in Oracle NDM
Hi to all,
I have Oracle 10g R2, I'm working on Oracle Network Data Model. I created a Network (named ITALIA_NET) based on links table (named ITALIA_LINK$) and nodes table (named ITALIA_NODE$).
Until now I computed the shortest path between two nodes using the 10gR2 NDM Java API, in particular I used the shortestPath() method.
I know that this method computes the shortest path between two nodes on the base of the values of a field that can be the lenght OR the travel time of the links.
What I wish to do is compute the shortest path between two nodes with a function that considers ( at the same time ) more parameters and on the base of them returns a path. For example, I want compute the shortest path taking into account these parameters for the links:
travel times of links
gradient links
tortuosity links
Infact, I have for each link the costs of: travel time (for example 3 minuts for cross the link), gradient (for example, the link has 2% of gradient) and tortuosity (for example, the link has two curves of 60° of angle).
Do you have any idea how I can implement this?
Are there other ways for reach this objective?
I hope I explained well my objective.
Thank you very much to all in advance._1) If I convert the values of the other cost columns into the values of the primary cost column (time is ok), what is the formulation for do this conversion?_
The modeling part is the most difficult part. I am not sure if there is a universal conversion formula between two different costs.
One recommendation is to use time as your primary cost.
For any other secondary costs, collect some data (or from some published statistics) on how these costs affect the travel time (based on the actual speeds wrt to gradients and tortuosity).
I am not an expert on this. Maybe asking questions like,
Q. how will a road of gradient = 10 deg affect the speed, uphill and downhill compared to the speed limit?
Once you have a good estimates on the speeds, you can compute the travel times as the distance/length of the link is known. The same applies to tortuosity,
Q. how will roads with 30/60/90 deg angles affect the travel speeds compared to the speed limit?
Assuming you are using something like the speed limit as you normal travel speed to compute your travel time.
_2) After conversion, how can I combine these columns?_
Say if you have done the conversion part in Step 1, you have 3 costs,
cost1, cost2, and cost3
You can create a view on the link table with the combined link cost as (cost1+cost2+cost4) or
you can create a new column that sums up the costs you want and use it as the link cost.
hope it helps!
jack -
I have this table:
with t as (
select 'A' source, 'B' destination, 7 meter from dual
union all
select 'A' source, 'C' destination, 9 meter from dual
union all
select 'A' source, 'F' destination, 14 meter from dual
union all
select 'B' source, 'C' destination, 10 meter from dual
union all
select 'B' source, 'D' destination, 15 meter from dual
union all
select 'C' source, 'D' destination, 11 meter from dual
union all
select 'C' source, 'F' destination, 2 meter from dual
union all
select 'D' source, 'E' destination, 6 meter from dual
union all
select 'E' source, 'F' destination, 9 meter from dual
select * from t;How to know the shortest path from a source to a destination? Suppose, from A to F. Can we show the shortest path using SQL? tx in advance.Billy Verreynne wrote:
I dislike what I consider blatant non-SQL features in SQL. Basic XML functionality is not an issue for me. But XQuery and modelling clauses - that I dislike.I can understand that.
Note that for the particular case we're discussing here, if I were to implement it in 11.2, I'd surely choose the recursive factoring approach instead.
I agree, most of these XML features may appear powerful and "cool" but also "evil" (as you would say) if they're not understood and used correctly.
BTW, for the record, the XQuery expression I posted is rewritten using SQL internal functions, so not much left of XML functionalities after all (except the name perhaps?).
So, I guess that makes it appears less evil ;)
SQL> explain plan for
2 select source
3 , destination
4 , meter
5 , xmlcast(
6 xmlquery('sum(for $i in ora:tokenize($s,";") return xs:integer($i))'
7 passing path as "s"
8 returning content
9 ) as number
10 ) as "SUM"
11 from (
12 select level, t.*, sys_connect_by_path(meter, ';') path
13 from paths t
14 where destination = 'F'
15 connect by prior destination = source
16 start with source = 'A'
17 )
18 order by "SUM"
19 ;
Explained.
SQL> set pages 100
SQL> set lines 140
SQL> select * from table(dbms_xplan.display(format => 'ALL'));
PLAN_TABLE_OUTPUT
Plan hash value: 2102804061
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | SELECT STATEMENT | | 9 | 18189 | 4 (25)| 00:00:01 |
| 1 | SORT AGGREGATE | | 1 | 2 | | |
| 2 | COLLECTION ITERATOR PICKLER FETCH | XQSEQUENCEFROMXMLTYPE | 8168 | 16336 | 29 (0)| 00:00:01 |
| 3 | SORT ORDER BY | | 9 | 18189 | 4 (25)| 00:00:01 |
| 4 | VIEW | | 9 | 18189 | 4 (25)| 00:00:01 |
|* 5 | FILTER | | | | | |
|* 6 | CONNECT BY NO FILTERING WITH START-WITH| | | | | |
| 7 | TABLE ACCESS FULL | PATHS | 9 | 171 | 3 (0)| 00:00:01 |
Query Block Name / Object Alias (identified by operation id):
1 - SEL$33CAA0FD
2 - SEL$33CAA0FD / KOKBF$@SEL$AEEEB114
3 - SEL$1
4 - SEL$2 / from$_subquery$_001@SEL$1
5 - SEL$2
7 - SEL$3 / T@SEL$3
Predicate Information (identified by operation id):
5 - filter("DESTINATION"='F')
6 - access("SOURCE"=PRIOR "DESTINATION")
filter("SOURCE"='A')
Column Projection Information (identified by operation id):
1 - (#keys=0) SUM(SYS_XQ_ATOMCNVCHK(TO_NUMBER(SYS_XQ_UPKXML2SQL(VALUE(KOKBF$),2,1,0)),2,33))[22]
2 - VALUE(A0)[40]
3 - (#keys=1) CAST(TO_CHAR( (SELECT SUM(SYS_XQ_ATOMCNVCHK(TO_NUMBER(SYS_XQ_UPKXML2SQL(VALUE(KOKBF$),2,1,0
)),2,33)) FROM TABLE() "KOKBF$")) AS number )[22], "SOURCE"[CHARACTER,1],
"DESTINATION"[CHARACTER,1], "METER"[NUMBER,22]
4 - "SOURCE"[CHARACTER,1], "DESTINATION"[CHARACTER,1], "METER"[NUMBER,22], "PATH"[VARCHAR2,4000]
5 - SYS_CONNECT_BY_PATH(TO_CHAR("METER"),';')[4000]
6 - "SOURCE"[CHARACTER,1], "DESTINATION"[CHARACTER,1], STRDEF[1], STRDEF[1], STRDEF[22], STRDEF[1],
STRDEF[1], STRDEF[22], PRIOR NULL[1], LEVEL[4], SYS_CONNECT_BY_PATH(TO_CHAR("METER"),';')[4000]
7 - "SOURCE"[CHARACTER,1], "T"."DESTINATION"[CHARACTER,1], "T"."METER"[NUMBER,22]
Note
- dynamic sampling used for this statement (level=2)
49 rows selected. -
Shortest Path Algorithm. Need help.
Hey, Im having trouble coming up with an algorithm for a shortest path. I have an NxN weighted matrix and need to get from the upper left corner to the lower right corner. The length of the path must be the shortest possible for the number of moves and total weight (ie. a 3X3 matrix would use 4 moves, a 4X4 uses 6 and a 5X5 uses 8).
im using a 2-dimensional array like matrix[x][y] with the storage at this location being a random integer.
I came up with some guidelines:
1) the path can never move left because it would break the shortest moves requirement.
2) the path can never move up for the same reason.
when traversing through the matrix if x == N then go down to N,N. If y == n go right until N,N.
I can visualize how to do it. Its just putting my algorithm into a program is beyond me right now.
Any help would be appreciated greatly.Dijkstra's algorithm only works on a weighted graph.
I have a weighted matrix.
Its like a chess board where every square has a
number on it. I have to get from the upper left to
the lower right using as little squares as possible
and then amongst those paths find the one with the
smallest weight or total.So something where individual squares have a certain toughness to get through, then?
Yeah, A* will own that...
I really don't want to write a tutorial on how to find the shortest path. But basically, you need to have a queue of paths. For each iteration until you find your goal, you pop the path with the least cost and you find the four paths you could get from it (move up, down, left, and right).
The key here is the cost function (heuristic). It must approximate the actual cost of a path WITHOUT over-approximating.
For your problem, you should probably factor in cost of the path so far, and the lowest possible expectable distance from the end of the path you're considering to the goal (think "distance formula").
Also, since these are general algorithms, you should probably code them up to work with an arbitrary start/end, instead of concrete values.
~Cheers -
Query for finding shortest path
I know nothing about Oracle Spatial. Just want to know if this query is possible using Spatial.
Given the following data for undirected weighted graph,
v1: vertex 1
v2: vertex 2
w: weight between vertices v1 and v2(or, distance of edge)
table name : wgraph
v1 v2 w
k a 2
m a 3
k c 1
k d 4
c b 2
h d 3
c h 3
h e 4
e b 4
m b 6Can I make a query which gives the shortest path from vertex 'a' to vertext 'e' using Spatial?
If this possible, that query gives the following result. (row-spanning form)
I think this is almost impossible using just a hierachical query.
Any method for this in Oracle Spatial?
spath
a
k
c
b
e
This is not a sort of homework or exam, just my interest.
Thx in advance.
Query Your Dream & Future at
http://www.soqool.comyes why not! in your case just create a logical network- called LRS Network and insert your vertices in node- table and additional information plus cost in the link table.
you can find ways using by dijkstra and A* -
Fitness for Shortest path using a genetic algorithm
Hi.
I have this problem:
I'm doing a program that has a map and two points. the map has wall that are not valid positions.
I have used a A* algorithm to calculate the shortest path and is working fine.
now i'm implementing a genetic algorithm to solve the problem but i'm not having sucess.
My genetic operator are directions (left, right, up and down).
I'm not being able to find a goodfitness function to solve the problem.
can someone tell me a god function or here I can found information about that?
I have been searching on google and I have not yet had sucess.
I have tryed two diferent fitness tecniques:
- add 1 for each step and if it finds a wall or gets out of the map add the maximum value (mapsize*mapsize).
- the other one is add the valid steps and if it finds a wall or gets out of the map add the number of necessary steps to gets to destination. the valid steps has a weight of 30% and the necessary steps has a weight of 70% (i have tryed to use diferent weight).
Can someone help me?
thanksHow about adapting your TSP code as follows. Your graph G(V, E) has two special vertices: v_s and v_d (start and destination). Let a candidate solution consist of a permutation of V\{v_s, v_d}u{v_m} where v_m is a new marker vertex whose purpose is to allow you to treat part of the candidate solution as irrelevant. Given candidate solution v_0 v_1 v_2 ... v_n v_m v_n+1 ... the weight is c(v_s, v_0) + c(v_0, v_1) + ... + c(v_n-1, v_n) where c(v_a, v_b) is the cost of the edge ab.
-
Finding the shortest path router for the router tracking purpose
Hi all,
A Question asking you regarding to routers' tracking information.
We keeps all the router infomation of our subnet in a file name "routers.txt" in this format:
1 2 1
2 4 1
4 3 1
1 3 5
This states there are four routers, the distance between routers 1 and 2 is 1, between 2 and 4 is 1, etc.
I need to write a Java program to keep track the shortest path between routers, I would understand that we can get this done easily in Java, but I am not a Java Savvy. I'm new in Java, would somebody help me to the right direction?
In order to keep track the routers in our subnet easily,the output would look something like:
Router 1
To Router Distance Vector
2 1 2
3 3 2
4 2 2
Thanks very much,
Cait.Hi kksenji,
Well, because of the webform, it's not obvious to see. The output would be simple. From the input, for router 1 to router 2, the shortest distance is 1. For router 1 to router 3, the shortest distance is 3, for router 1 to router 4, the shortest distance is 2 and so on. The middle vector that it went through is 2 for every route. Hope this makes sense.
Just try to solve the problem with the shortest distance, and I have a hard time to figure out the algorithm for this as well as how to get this started.
Thanks, Cait. -
Hey guys,
Im working on a solution to this problem below is a program to allow a user to draw straight line paths. What i'd like to do is allow the user to select two points on the path he has drawn and find the shortest path among all the interesecting lines.....im going crazy thinking of a solution for this.....im thinking bout steeping down a notch and just try to find just any path first.
Will really appreciate any help.
Thnx in advance,
Vikhyat
import java.applet.*;*
*import java.awt.*;
import java.awt.event.*;*
*import javax.swing.*;
import java.awt.geom.*;
public class Lab11 extends Applet implements MouseListener, MouseMotionListener {
int x0, y0, x1, y1;
int mouseRelease=0;
GeneralPath path = new GeneralPath();
public Lab11()
addMouseListener(this);
addMouseMotionListener(this);
public void mouseDragged(MouseEvent e)
x1 = e.getX();
y1 = e.getY();
repaint();
public void mouseMoved(MouseEvent e) { }
public void mouseClicked(MouseEvent e) { }
public void mouseEntered(MouseEvent e) { }
public void mouseExited (MouseEvent e) { }
public void mousePressed(MouseEvent e) {
x0 = e.getX();
y0 = e.getY();
System.out.println("Mouse pressed at: (" +
x0 + ", " + y0 + ")" );
public void mouseReleased(MouseEvent e) {
x1 = e.getX();
y1 = e.getY();
System.out.println("Mouse released at: (" +
x1 + ", " + y1 + ")" );
mouseRelease = 1;
this.repaint();
public void paint(Graphics g)
Graphics2D g2 = (Graphics2D)g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
//just for show not concerned with saving paths
if(mouseRelease==1)
path.moveTo(x0,y0);
path.lineTo(x1,y1);
mouseRelease = 0;
g2.setPaint(Color.RED);
g2.draw(path);
g.setColor(Color.BLACK);
g.drawLine(x0, y0, x1, y1);
public static void main(String[] argv)
JFrame f = new JFrame("Test");
f.getContentPane().add(new Lab11());
f.setSize(600,600);
f.setVisible(true);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}Pictorially this is what im trying to do:
User draws a path like so and selects two points as shown in blue
[http://i48.photobucket.com/albums/f236/theforrestgump/select.jpg]
The program should then proceed to highlighting the shortest path
[http://i48.photobucket.com/albums/f236/theforrestgump/sp.jpg]
Edited by: cannonball on Apr 1, 2008 7:58 PMimport java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import javax.swing.*;
public class ShortPath extends JPanel {
Path2D.Double path;
Path2D.Double shortPath = new Path2D.Double();
Point p1 = new Point();
Point p2 = new Point();
final double PROXIMITY = 5.0;
public ShortPath() {
path = new Path2D.Double();
path.moveTo(145,80);
path.lineTo(125,170);
path.lineTo(190,200);
path.lineTo(240,340);
path.lineTo(285,220);
path.lineTo(145,80);
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D)g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
g2.setPaint(Color.blue);
g2.draw(path);
g2.setPaint(Color.green);
g2.setStroke(new BasicStroke(2f));
g2.draw(shortPath);
g2.setPaint(Color.red);
g2.fill(new Ellipse2D.Double(p1.x-2, p1.y-2, 4, 4));
g2.setPaint(Color.orange);
g2.fill(new Ellipse2D.Double(p2.x-2, p2.y-2, 4, 4));
private void findShortPath() {
if(!isPointOnLine(p1) || !isPointOnLine(p2)) {
System.out.println("a point is not on the path");
return;
double d1 = getDistanceToPoint(p1);
double d2 = getDistanceToPoint(p2);
double pathLength = getDistanceToPoint(new Point());
Point2D.Double start = new Point2D.Double();
Point2D.Double end = new Point2D.Double();
if((d1 < d2 && d2 - d1 < pathLength - d2 + d1) ||
(d1 > d2 && d1 - d2 > pathLength - d1 + d2)) {
start.setLocation(p1);
end.setLocation(p2);
} else {
start.setLocation(p2);
end.setLocation(p1);
generatePath(start, end);
// 145,80
// leg distance = 92.2 125,170
// leg distance = 71.6 190,200 163.8
// leg distance = 148.7 240,340 312.5
// leg distance = 128.2 285,220 440.7
// leg distance = 198.0 145,80 638.7
private double getDistanceToPoint(Point p) {
PathIterator pit = path.getPathIterator(null);
double[] coords = new double[2];
double distance = 0;
Point2D.Double start = new Point2D.Double();
Point2D.Double end = new Point2D.Double();
Line2D.Double line = new Line2D.Double();
while(!pit.isDone()) {
int type = pit.currentSegment(coords);
switch(type) {
case PathIterator.SEG_MOVETO:
start.setLocation(coords[0], coords[1]);
pit.next();
continue;
case PathIterator.SEG_LINETO:
end.setLocation(coords[0], coords[1]);
line.setLine(start, end);
boolean onLine = line.ptSegDist(p) < PROXIMITY;
if(onLine) { // point is on this line
distance += start.distance(p);
break;
} else {
distance += start.distance(end);
start.setLocation(end);
pit.next();
return distance;
private void generatePath(Point2D.Double first, Point2D.Double second) {
Point2D.Double p = new Point2D.Double(first.x, first.y);
Point2D.Double start = new Point2D.Double();
Point2D.Double end = new Point2D.Double();
Line2D.Double line = new Line2D.Double();
boolean pathStarted = false;
for(int j = 0; j < 2; j++) {
PathIterator pit = path.getPathIterator(null);
double[] coords = new double[2];
while(!pit.isDone()) {
int type = pit.currentSegment(coords);
switch(type) {
case PathIterator.SEG_MOVETO:
start.setLocation(coords[0], coords[1]);
pit.next();
continue;
case PathIterator.SEG_LINETO:
end.setLocation(coords[0], coords[1]);
line.setLine(start, end);
boolean onLine = line.ptSegDist(p) < PROXIMITY;
if(onLine) { // found point on line
Point2D.Double linePt = getClosestPoint(line, p);
Line2D.Double segment;
if(!pathStarted) { // found first point
// both points on line
if(line.ptSegDist(second) < PROXIMITY) {
Point2D.Double secPt =
getClosestPoint(line, second);
segment = new Line2D.Double(linePt, secPt);
shortPath.append(segment, false);
return;
} else { // first point only
segment = new Line2D.Double(linePt, end);
shortPath.append(segment, false);
p.setLocation(second);
pathStarted = true;
} else { // found second point
segment = new Line2D.Double(start, linePt);
shortPath.append(segment, false);
return;
} else if(pathStarted) {
// add intermediate lines
Line2D.Double nextLine =
new Line2D.Double(start, end);
shortPath.append(nextLine, false);
start.setLocation(end);
pit.next();
private Point2D.Double getClosestPoint(Line2D.Double line,
Point2D.Double p) {
double minDist = Double.MAX_VALUE;
Point2D.Double closePt = new Point2D.Double();
double dy = line.getY2() - line.getY1();
double dx = line.getX2() - line.getX1();
double theta = Math.atan2(dy, dx);
double length = line.getP2().distance(line.getP1());
int limit = (int)(length+.05);
for(int j = 0; j < limit; j++) {
double x = line.getX1() + j*Math.cos(theta);
double y = line.getY1() + j*Math.sin(theta);
double distance = p.distance(x, y);
if(distance < minDist) {
minDist = distance;
closePt.setLocation(x, y);
return closePt;
private boolean isPointOnLine(Point p) {
Point2D.Double start = new Point2D.Double();
Point2D.Double end = new Point2D.Double();
Line2D.Double line = new Line2D.Double();
PathIterator pit = path.getPathIterator(null);
double[] coords = new double[2];
while(!pit.isDone()) {
int type = pit.currentSegment(coords);
switch(type) {
case PathIterator.SEG_MOVETO:
start.setLocation(coords[0], coords[1]);
pit.next();
continue;
case PathIterator.SEG_LINETO:
end.setLocation(coords[0], coords[1]);
line.setLine(start, end);
if(line.ptSegDist(p) < PROXIMITY) {
return true;
start.setLocation(end);
pit.next();
return false;
public static void main(String[] args) {
ShortPath test = new ShortPath();
test.addMouseListener(test.ml);
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(test);
f.setSize(400,400);
f.setLocation(200,200);
f.setVisible(true);
private MouseListener ml = new MouseAdapter() {
boolean oneSet = false;
public void mousePressed(MouseEvent e) {
Point p = e.getPoint();
if(oneSet) {
p2 = p;
findShortPath();
} else {
p1 = p;
shortPath.reset();
oneSet = !oneSet;
repaint();
} -
Dispay shortest path in MapViewer
Hello,
I had sucsessfully installed MapViewer 9.0.4 and Oracle Spatial 10g.
here I would like to know how to make a shortest path query between two point in Oracle MapViewer and display it.
Any help will be appreciated.
regards
azizHi Aziz,
the next release of MapViewer will support the Network Model including requests ro render shortest paths. -
Hi all,
I have created spatial network containing non lrs sdo_geometry objects in Oracle 10g (Release 2). In this network model there are 33208 nodes and 42406 links.
Now I need to write a java program to find shortest route between two selected nodes. Here is snippet of my source code.
Connection connection = DriverManager.getConnection(dbUrl, databaseUser, databasePassword);
boolean readForUpdate = false;
Network net= NetworkManager.readNetwork(connection, "SDO_ROAD_NETWORK", readForUpdate);
Path path = NetworkManager.shortestPath(net, startNodeId ,endNodeId);
System.out.println ("total distance " path.getCost() );+
Link[] linkArray = path.getLinkArray();
But this will throws an exception - Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
It was working fine for 1000 nodes and 1000 links. I tried by changing java options like -Xms and Xmx parameters but same result.
Then I tried to find shortest route using pl/sql using following.
DECLARE
testNet VARCHAR2(30) := 'SDO_ROAD_NETWORK';
startNode NUMBER := 120150;
endNode NUMBER :=1740034;
path NUMBER;
linkArray SDO_NUMBER_ARRAY;
BEGIN
sdo_net_mem.network_manager.read_network('SDO_ROAD_NETWORK', 'FALSE');
dbms_output.put_line('Loading finished');
path := SDO_NET_MEM.NETWORK_MANAGER.SHORTEST_PATH_DIJKSTRA('SDO_ROAD_NETWORK', startNode, endNode);
IF path IS NULL THEN
dbms_output.put_line('route not found');
return;
END IF;
linkArray := SDO_NET_MEM.PATH.GET_LINK_IDS(testNet, path);
FOR i IN linkArray.first..linkArray.last
LOOP
dbms_output.put_line('Link -- ' || linkArray(i) || ' ' ||
SDO_NET_MEM.LINK.GET_NAME (testNet, linkArray(i)) || ' ' ||
SDO_NET_MEM.LINK.GET_COST (testNet, linkArray(i)));
END LOOP;
END;
+/+
But this takes nearly 4 minutes to just read the nework (sdo_net_mem.network_manager.read_network).
Finally I dowloaded standalone java client application NDM Network Editor from OTN. This application loads entire network within 25 seconds and finds shortest route within 5 seconds.
Please guide me how can I write improved code reading network. My requirement is to get shortest path between two nodes
Thanks,
SujnanHi Sujnan
In the past there have been some performance issue for the Oracle JVM. Not sure if this addressed in the latest releases (10.r2 or 11).
Performance Status OJVM used for SDO Network data Model 10R2.0.2
Maybe the oracle guys can give an update.
Luc -
Aco implemenataion for shortest paths.
has anyone used ant colony optimization algorithm for finding shortest paths other than for the tsp? please i need some help and advice. thanks
sorry for not being specific and the insubsequent reply. am just doing some research on aco, i want to try and implement it for best bath planning on a map/graph. I've been looking around for some example on such and noticed that this algorithm is mainly used for tsp problem which got me questioning the possibility of my task. I just want to know if it is definitely possible with aco as i will give it a go in this case. Implementing this algorthm successfully is the main challenge of my project so i cannot contemplate another algorithm option. Thanks for your time.
-
Hi experts,
Is it possible to write the code for the "Shortest path problem" in ABAP?If yes, what is the code?
Moderator Message: Don't expect members to spoon-feed you
Edited by: Suhas Saha on Jul 25, 2011 11:13 AMHi munish,
I dont think there is any thing wrong with the ABAP code.
Try testing your ABAP mapping using transaction code SXI_MAPPING_TEST in XI.
Enter the Details asked and then enter TEst data in XML format..
Also, you can make use of the Trace element to find out if there is any thing wrong with the code.
Include the following Statements after every step in the ABAP code to ensure that the particular step is completed successfully.
data : l_trace type string.
concatenate l_trace '<Message you want to display>' into l_trace.
trace->trace(level = '<level>'
message =l_trace).
The trace is visible in SXMB_MONI (click on "Trace" in the left pane to view).
using this you will get to know i the code is functioning as desired.
Regards,
Yashaswee. -
Hey guys, first...Happy thanksgiving :)
Ok, so I'm on my last assignment for my amazingly taught Data Structures class. I battled my way successfully through recursion, binary trees, redblack trees, 234 trees, B Trees, and heaps!...no issues at all!....but, now I have hit graphs. I understand the concept, but my latest assignment has me a bit frustrated..Im so close to finishing I can taste it!!....I just cant find the spoon..
Here we go:
We are given a graph on paper. It has circles (verteci) representing cities in the USA. These circles are connected by lines (edges) representing the distance between the cities. Also, the lines have arrows pointing the direction they may be traversed.
We are to construct the graph in the computer, and then compute the shortest path from washington (Vertex 0) to every other city.
I managed to construct the graph, and it will find the shortest path no problem. My only issue is that, it wants us to print the path it took, not just the destination and total distance....
I have tried using a stack to push the verteci onto as theyre visited, but im not getting happy results.
I should also mention, this code is taken out of the book with modifications by me so that it can add edges and verteci, and it now accepts String types for the vertex labels instead of characters.
Here is my code
PATH.JAVA (the important part)
// path.java
// demonstrates shortest path with weighted, directed graphs
// to run this program: C>java PathApp
import java.lang.*;
import java.io.*;
class DistPar // distance and parent
{ // items stored in sPath array
public int distance; // distance from start to this vertex
public int parentVert; // current parent of this vertex
public DistPar(int pv, int d) // constructor
distance = d;
parentVert = pv;
} // end class DistPar
class Vertex
public String label; // label (e.g. 'A')
public boolean isInTree;
public Vertex(String lab) // constructor
label = lab;
isInTree = false;
} // end class Vertex
class Graph
private final int MAX_VERTS = 20;
private final int INFINITY = 1000000;
private Vertex vertexList[]; // list of vertices
private int adjMat[][]; // adjacency matrix
private int nVerts; // current number of vertices
private int nTree; // number of verts in tree
private DistPar sPath[]; // array for shortest-path data
private int currentVert; // current vertex
private int startToCurrent; // distance to currentVert
private stack path_taken; // stack to record path taken
public Graph() // constructor
vertexList = new Vertex[MAX_VERTS];
// adjacency matrix
adjMat = new int[MAX_VERTS][MAX_VERTS];
nVerts = 0;
nTree = 0;
for(int j=0; j<MAX_VERTS; j++) // set adjacency
for(int k=0; k<MAX_VERTS; k++) // matrix
adjMat[j][k] = INFINITY; // to infinity
sPath = new DistPar[MAX_VERTS]; // shortest paths
path_taken = new stack(MAX_VERTS);
} // end constructor
public void addVertex(String lab)
vertexList[nVerts++] = new Vertex(lab);
public void addEdge(int start, int end, int weight)
adjMat[start][end] = weight; // (directed)
public void path() // find all shortest paths
int startTree = 0; // start at vertex 0
vertexList[startTree].isInTree = true;
nTree = 1; // put it in tree
// transfer row of distances from adjMat to sPath
for(int j=0; j<nVerts; j++)
int tempDist = adjMat[startTree][j];
sPath[j] = new DistPar(startTree, tempDist);
// until all vertices are in the tree
while(nTree < nVerts)
int indexMin = getMin(); // get minimum from sPath
int minDist = sPath[indexMin].distance;
if(minDist == INFINITY) // if all infinite
{ // or in tree,
System.out.println("There are unreachable vertices");
break; // sPath is complete
else
{ // reset currentVert
currentVert = indexMin; // to closest vert
startToCurrent = sPath[indexMin].distance;
// minimum distance from startTree is
// to currentVert, and is startToCurrent
// put current vertex in tree
vertexList[currentVert].isInTree = true;
nTree++;
path_taken.push(sPath[indexMin]);
adjust_sPath(); // update sPath[] array
} // end while(nTree<nVerts)
displayPaths(); // display sPath[] contents
nTree = 0; // clear tree
for(int j=0; j<nVerts; j++)
vertexList[j].isInTree = false;
} // end path()
public int getMin() // get entry from sPath
{ // with minimum distance
int minDist = INFINITY; // assume minimum
int indexMin = 0;
for(int j=1; j<nVerts; j++) // for each vertex,
{ // if it's in tree and
if( !vertexList[j].isInTree && // smaller than old one
sPath[j].distance < minDist )
minDist = sPath[j].distance;
indexMin = j; // update minimum
} // end for
return indexMin; // return index of minimum
} // end getMin()
public void adjust_sPath()
// adjust values in shortest-path array sPath
int column = 1; // skip starting vertex
while(column < nVerts) // go across columns
// if this column's vertex already in tree, skip it
if( vertexList[column].isInTree )
column++;
continue;
// calculate distance for one sPath entry
// get edge from currentVert to column
int currentToFringe = adjMat[currentVert][column];
// add distance from start
int startToFringe = startToCurrent + currentToFringe;
// get distance of current sPath entry
int sPathDist = sPath[column].distance;
// compare distance from start with sPath entry
if(startToFringe < sPathDist) // if shorter,
{ // update sPath
sPath[column].parentVert = currentVert;
sPath[column].distance = startToFringe;
column++;
} // end while(column < nVerts)
} // end adjust_sPath()
public void displayPaths()
for(int j=0; j<nVerts; j++) // display contents of sPath[]
System.out.print(vertexList[j].label + "="); // B=
if(sPath[j].distance == INFINITY)
System.out.print("inf"); // inf
else
System.out.print(sPath[j].distance); // 50
String parent = vertexList[ sPath[j].parentVert ].label;
System.out.print(" (" + parent + ") "); // (A)
System.out.println("");
System.out.println("PRINTING path_taken");
DistPar thing = null;
while((thing = path_taken.pop()) != null)
System.out.println(" " + vertexList[thing.parentVert].label + " "+ thing.distance);
} // end class GraphSTACK.JAVA (my stack class)
// stack.java
// demonstrates stacks
// to run this program: C>java StackApp
class stack
private int maxSize; // size of stack array
private DistPar[] stackArray;
private int top; // top of stack
public stack(int s) // constructor
maxSize = s; // set array size
stackArray = new DistPar[maxSize]; // create array
top = -1; // no items yet
public void push(DistPar j) // put item on top of stack
stackArray[++top] = j; // increment top, insert item
public DistPar pop() // take item from top of stack
return stackArray[top--]; // access item, decrement top
public DistPar peek() // peek at top of stack
return stackArray[top];
public boolean isEmpty() // true if stack is empty
return (top == -1);
public boolean isFull() // true if stack is full
return (top == maxSize-1);
}PATHAPP.JAVA (test program..builds the graph and calls path())
class PathApp
public static void main(String[] args)
Graph theGraph = new Graph();
theGraph.addVertex("Washington");
theGraph.addVertex("Atlanta");
theGraph.addVertex("Houston");
theGraph.addVertex("Denver");
theGraph.addVertex("Dallas");
theGraph.addVertex("Chicago");
theGraph.addVertex("Austin");
theGraph.addEdge(0,1,600);
theGraph.addEdge(1,0,600);
theGraph.addEdge(0,4,1300);
theGraph.addEdge(4,3,780);
theGraph.addEdge(3,1,1400);
theGraph.addEdge(1,2,800);
theGraph.addEdge(2,1,800);
theGraph.addEdge(4,5,900);
theGraph.addEdge(4,6,200);
theGraph.addEdge(6,4,200);
theGraph.addEdge(6,2,160);
theGraph.addEdge(3,5,1000);
theGraph.addEdge(5,3,1000);
System.out.println("Shortest Paths");
theGraph.path();
//theGraph.displayPaths();
System.out.println();
}Im mostly having trouble comprehending the Path.java file. A few friends and I stared at it for a few hours and couldnt get it to do what we wanted...
path_taken is the stack I added in to try and push/pop the verteci as theyre traversed, but with what I stuck in right now, it still just prints the most recently visited vertex, and the sum of the distances.
Any help is greatly appreciated!
Thanks :)
----ArkhanIf your graph is G(V, E), and you're trying to get to vertex v_end, then create a new graph G'(V', E') whereV' = (V x N) U {v_end'}
(v_end' is a new object)
E' = {((u, t), (v, t + f(u, v, t))) : (u, v) in E, t in N} U
{((u, t), (u, t + 1)) : u in V, t in N} U
{((v_end, t), v_end') : t in N}G' is infinite, so you'll need to use a lazy graph structure. Then just use Dijkstra from (v_start, 0) to v_end'. -
Hi
I have created a topological network in Oracle Spatial and now
I am trying to find the shortest path between two nodes.
Is there a sample java code (or instructions) that connects to the database
and gets that information?
Thank uOracle Spatial NDM Java API has several shortest path analysis functions. A simple example is as follows.
// establish JDBC connection: you need specify dbURL, user1, password1
OracleDataSource ods1 = new OracleDataSource();
ods1.setURL(dbURL);
ods1.setUser(user1);
ods1.setPassword(password1);
Connection conn1 = ods1.getConnection();
// read in network, netName is the name of your network in the database
Network net = NetworkManager.readNetwork(conn1, netName);
// perform shortestPath analysis
Path path = NetworkManager.shortestPath(net, startNodeID, endNodeID);
// then from Path interface, you can access its constituent link/node information
} -
hello,
We have a street-layer (spatial). Now we should calculate the shortest path between two nodes. Does Oracle assist in this? Has anybody some experiences with this problem?
Any help will be appreciated.
regards
AnnaWell, I know there are several algorithms for this problem, but I wanted to know, if and how Oracle assist�s in this point. I get an answer from Oracle, that 10g include such functionality and now I am waiting on it.
Thanks for your try to help.
Monika-Anna
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