Trace_back

syntax

trace_back(F1, F2, dijkstra/traceback, capacity)

definition

trace_back(F1, F2, dijkstra/traceback, capacity) calculates flows in a network.

Based on the results of dijkstra calculations, the trace_back function results in the amount of flow for each link in the network.

The trace_back function requests four arguments:

F1: relation to the from node of each link;
F2: relation to the to node of each link;
dijkstra/traceback: the node to edge traceback item, a generated subitem by the dijkstra function
capacity: capacity indicator for each node.

applies to

attributes F1, F2 and dijkstra/traceback with uint32 value-type
attribute capacity with Numeric value type

conditions

The domain-unit of attributes F1 and F2 must match.

example

attribute<meter> dist (NodeSet) := dijkstra(dist, F1, F2, nr_DestNode);
attribute<nr_pers> flow (LinkSet) :=
   value(
      trace_back(
           F1
         , F2
         , dist/TraceBack
         , pcount(nr_OrgNode)
      )
      , nr_pers
   );

F1	F2	flow
8	7	0
1	4	2
16	15	0
2	3	1
5	4	1
6	7	2
9	10	1
12	11	1
14	15	0
18	20	1
19	17	1
3	0	0
4	11	1
7	1	2
10	3	1
11	13	0
13	17	0
15	10	0
20	21	0
17	20	1

domain Linkset, nr of rows = 19

nr_OrgNode
14
12
9
18
5

domain Origin, nr of rows = 5

F1	F2	flow
8	7	0
1	4	2
16	15	0
2	3	1
5	4	1
6	7	2
9	10	1
12	11	1
14	15	0
18	20	1
19	17	1
3	0	0
4	11	1
7	1	2
10	3	1
11	13	0
13	17	0
15	10	0
20	21	0
17	20	1

F1	F2	flow
8	7	0
1	4	2
16	15	0
2	3	1
5	4	1
6	7	2
9	10	1
12	11	1
14	15	0
18	20	1
19	17	1
3	0	0
4	11	1
7	1	2
10	3	1
11	13	0
13	17	0
15	10	0
20	21	0
17	20	1

F1	F2	flow
8	7	0
1	4	2
16	15	0
2	3	1
5	4	1
6	7	2
9	10	1
12	11	1
14	15	0
18	20	1
19	17	1
3	0	0
4	11	1
7	1	2
10	3	1
11	13	0
13	17	0
15	10	0
20	21	0
17	20	1