File formats for the 9th DIMACS Implementation Challenge

In this page we describe the standard file format conventions for the 9th DIMACS Implementation Challenge. To accommodate different problem types, we specify a problem using a graph file and zero or more problem-specific auxiliary files. For each specification file we use the following conventions:

Files consist of ASCII characters (plain text files)
The file content consists of several types of lines
Each line begins with a one-character line type designator
Line fields are separated by at least one blank space
Each line ends with a newline separator
Numerical values stored in the file (e.g., arc weights, node ids, etc.) may be strings of digits of any length. Programs should make sure to load them into large enough memory words (e.g., 32 or 64 bits depending on the context).

Input graph (.gr files)		View sample.gr
A graph contains n nodes and m arcs Nodes are identified by integers 1...n Graphs can be interpreted as directed or undirected, depending on the problem being studied Graphs can have parallel arcs and self-loops Arc weights are signed integers
By convention, shortest path graph file names should have the suffix .gr. Line types are as follows. In the format descriptions below, bold characters should appear exactly as typed:
Comment lines	These lines begin with a lower-case character c and can appear anywhere. Comment lines are ignored by programs.	c This is a comment
Problem line	The problem line is unique and must appear as the first non-comment line. This line has the format on the right, where n and m are the number of nodes and the number of arcs, respectively.	p sp n m
Arc descriptor lines	Arc descriptors are of the form on the right, where SRC and DST are the tail and the head node ids, respectively, and LEN is the arc weight.	a SRC DST LEN

Node coordinates (.co files)		View sample.co
X-Y coordinates in the plane associated with nodes of the graph can be stored in an auxiliary file having the same name of the graph file it is related to and extension .co. For instance, file mygraph.co would contain the node coordinates of graph mygraph.gr. Line types are as follows. In the format descriptions below, bold characters should appear exactly as typed:
Comment lines	These lines begin with a lower-case character c and can appear anywhere. Comment lines are ignored by programs.	c This is a comment
Problem line	The problem line is unique and must appear as the first non-comment line. This line has the format on the right, where n is the number of coordinate lines that follow.	p aux sp co n
Coord lines	Coordinate lines are of the form on the right, where id , X and Y are the id of the node, its X-coordinate, and its Y-coordinate, respectively.	v id X Y

Single-source shortest path problem (.ss files)		View sample.ss
The goal of the SSSP problem is to find shortest paths between a specified source node and all other nodes in the input graph. The auxiliary file for the problem should have the extension .ss. Line types are as follows. In the format descriptions below, bold characters should appear exactly as typed:
Comment lines	These lines begin with a lower-case character c and can appear anywhere. Comment lines are ignored by programs.	c This is a comment
Problem line	The problem line is unique and must appear as the first non-comment line. This line has the format on the right, where n is the number of source lines that follow.	p aux sp ss n
Source lines	Source lines are of the form on the right, where S is the id of the source node. If more than one source line in file.ss is specified, each line defines a new problem on the same graph with a different source.	s S
For the NSSSP problem, the format is the same as for the more general SSP problem, with the understanding that all arc lengths are nonnegative.

Point-to-point shortest path problem (.p2p files)		View sample.p2p
The goal of the P2P problem is to find a shortest path between a specified pair of nodes in the input graph. The auxiliary file for this problem should have the extension .p2p. Line types are as follows. In the format descriptions below, bold characters should appear exactly as typed:
Comment lines	These lines begin with a lower-case character c and can appear anywhere. Comment lines are ignored by programs.	c This is a comment
Problem line	The problem line is unique and must appear as the first non-comment line. This line has the format on the right, where n is the number of query lines that follow.	p aux sp p2p n
Query lines	Query lines are of the form on the right, where S, T are the ids of the source and the destination nodes, respectively. Each query line defines a new problem on the same graph.	q S T

All-pairs shortest path problem

The goal of the APSP problem is to find shortest paths between each pair of nodes in the input graph. This problem is completely specified by the graph. No auxiliary file is used.

Negative cycle detection problem

The goal of the NCD problem is to find a negative cycle in the input graph, if one exists. This problem is completely specified by the graph. No auxiliary file is used.