## Graph File Formats:

The graph file formats include an **adjacency graph**
format, an **edge graph** format, and a **weighted
edge graph** format.
All formats are ascii and entries are delimited by any
consecutive sequence of delimiter characters: **tab**,
**space**, **line feed** (ascii 0x0A), and
**carriage return** (ascii 0x0D). Files can start and
end with delimiters, which are ignored. Throughout the description n
refers to the number of vertices and m to the number of edges in a
graph.

### Adjacency Graph

The adjacency graph format starts with a sequence of offsets one for
each vertex, followed by a sequence of directed edges ordered by their
source vertex. The offset for a vertex i refers to the location of
the start of a contiguous block of out edges for vertex i in the
sequence of edges. The block continues until the offset of the next
vertex, or the end if i is the last vertex. All vertices and offsets
are 0 based and represented in decimal. The specific format is as
follows:

`AdjacencyGraph`

<**o0**>

<**o1**>

...

<**o(n-1)**>

<**e0**>

<**e1**>

...

<**e(m-1)**>

### Edge Graph

The edge graph format consists of a sequence of edges/arcs each being
a pair of integers.
The format can either be interpreted as a directed graph or an undirected graphs
depending on the application.
Vertices are assumed to start at 0.
The specific format is as follows:

`EdgeArray`

<**s0**> <**t0**>

<**s1**> <**t1**>

...

<**s(n-1)**> <**t(n-1)**>

where <

**si**> and <

**ti**>
refer to the two endpoints of the undirected edge i, or the source and
target of a directed edge (arc) i.

### Weighted Edge Graph

The weighted edge graph format is the same as the edge graph format but
includes double precision floating point weights.
The specific format is as follows:

`WeightedEdgeArray`

<**s0**> <**t0**> <**w0**>

<**s1**> <**t1**> <**w1**>

...

<**s(n-1)**> <**t(n-1)**> <**w(n-1)**>

where <

**wi**> is the weight of edge i. The weight can either
be in decimal or exponential notation.

This project has been funded by the following sources:

Intel Labs Academic Research Office for the Parallel Algorithms for Non-Numeric Computing Program,

National Science Foundation, and

IBM Research.