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Instance files

This is the standard file format for PathWyse instances.

They can also be built programmatically, in both C++ and Python. See Creating an instance programmatically for a Python example.

Properties of instances can be described by defining the problem and the network with either atomic values, sequences or lists.

Only integer values are accepted, that is, if an instance has decimal values, we suggest to scale data beforehand.

Note that there is a strict order in the instance file:

  • Problem setup needs to be defined first
  • Network setup is defined second

Please refer to the instances provided in the instance folder for examples.

The format for atomic values and sequences is the following:

KEYWORD : value
The format for lists is instead: 
KEYWORD
list
END

Problem Setup

Keyword Description Value Type Example
NAME instance name text An-54
COMMENT comment text example
SIZE number of nodes integer 50
DIRECTED graph is directed 0 or 1 1
CYCLIC graph presents cycles 0 or 1 0
ORIGIN source node integers 0
DESTINATION destination node integers 17
RESOURCES number of resources (R) integers 3
RES_NAMES sequence of numerical ids (RES_ID) for each resource. From 0 to R-1 integers 0 1 2

Note that origin and destination are optional.

If no origin is specified, the solver will assume that node 0 is the origin.

If no destination is reported, PathWyse will duplicate the origin node.

Note that Resource 0 will always be the critical one in bi-directional search.

Example: 

NAME : NY
SIZE : 264346
DIRECTED : 1
CYCLIC : 0
ORIGIN : 0
DESTINATION : 17
RESOURCES : 1
RES_NAMES : 0
This means that this instance has 264346 nodes, the graph is directed and acyclic. There is just one resource, and we want to find the RCSPP from node 0 to node 17.

Network setup

Resources definition

Resource types

This section describes the resource types 

RES_TYPE    
RES_ID RES_TYPE         
END
Accepted RES_ID values are specified by RES_NAMES.

Accepted RES_TYPE values:

Keyword Resource Info
CAP Capacity Demand is collected on nodes only
TIME Time Can include travel time (arcs) and service time (nodes)
NODELIM Node limit Limits the length of Paths
TW Time Windows

Example: 

RES_TYPE    
0 CAP
1 CAP
2 NODELIM
3 TW
END
That is:

  • Resource 0 is of type capacity
  • Resource 1 is also a capacity resource
  • Resource 2 is a node limit
  • Resource 3 enforces time windows

Resource bounds

This section describes the lower and upper bounds for each resource: 

RES_BOUND   
RES_ID LB UB
END
Example:

RES_BOUND       
0 0 25
1 0 28
2 0 8
END

This means that:

  • Resource 0 has 0 as a lower bound and 25 as an upper bound
  • Resource 1 has 0 as a lower bound and 28 as an upper bound
  • Resource 2 has 0 as a lower bound and 8 as an upper bound
  • Resource 3 has no lower and upper bounds

Resource bounds on nodes

This section describes the lower and upper bounds on each nodes for resources. This is mostly useful for specifying arrival and departure times for time windows:

RES_NODE_BOUND
RES_ID NODE_ID LB UB
END
Example:

RES_NODE_BOUND
3 1 189 579
3 2 100 307
3 3 716 1033
3 4 503 604
...
END

This means that we are setting node bounds for Resource 3 (time windows, in this example). For example, node 1 expects an arrival time equal or greater than 189 and a departure time of 579.

Edges

Edge cost

Describe the objective function cost for the arc connecting node i to node j: 

EDGE_COST 
i j COST
END
Example: 
EDGE_COST
0 1 43000
0 5 54000
...
END
This means that the arc that goes from node 0 to node 1 (and vice versa, if the network is undirected) costs 43000, whilst arc 0-5 costs 54000, and so on.

Edge consumption

This list describes, for each resource, the resource consumption when traveling along the arc from node i to node j:

EDGE_CONSUMPTION
RES_ID i j RES_CONSUMPTION
END

Example: 

EDGE_CONSUMPTION
3 2 0 75
3 2 1 35
3 3 0 72
...
END

This means that travelling from node 2 to node 1, consumes 35 units of Resource 3.

Nodes

Node cost

This list describes the objective function cost for each node: 

NODE_COST
NODE_ID COST 
END
Example: 

NODE_COST
1 12000 
3 -48402
...
END
Meaning that node 1 will cost 12000, whilst node 3 will cost -48402.

Node consumption

This list describes, for each resource, the resource consumption at each node:

NODE_CONSUMPTION
RES_ID NODE_ID RES_CONSUMPTION
END

Example: 

NODE_CONSUMPTION
0 1 5
0 2 7
...
1 1 5
1 2 1
1 3 4
...
3 1 10
3 2 40
3 3 20
...
END

This means that:

  • Visiting node 1 consumes 5 units of Resource 0, 5 units of Resource 1 and 10 units of Resource 3.
  • Visiting node 2 consumes 5 units of Resource 0, 1 unit of Resource 1 and 40 units of Resource 3.

and so on.