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### sssp command

### sssp2 command

**Syntax:**

sssp N seed -i in1 -o out1.file out1.mr

sssp2 N seed -i in1 -o out1.file out1.mr

- N = # of random starting vertices to choose
- seed = random number seed (positive integer)
- in1 = graph edges: Key = Vi Vj, Value = weight
- out1 = distance to each vertex: Key = Vi, Value = distance

**Examples:**

sssp 10 12345 -i mre -o sssp.dist mrdist
sssp2 10 12345 -i mre -o sssp.dist mrdist

**Description:**

These are named commands which compute the shortest path to each
vertex from a source vertex in an undirected graph. This is called a
single-source shortest-path (SSSP) calculation. The source vertex is
selected randomly. Each edge in the graph has a weight. The
shortest-path distance to any other vertex is the minimum summed
weight of a list of consecutive edges that connect the two vertices.

This calculation involves a breadth-first search on the graph. The
MapReduce algorithms used for performing the SSSP calculation are
described in the paper of (Plimpton). The sssp command
implements the first of the two algorithms discussed in the paper.
The sssp2 command implements the second of the two algorithms.

See the named command doc page for various ways in which
the -i inputs and -o outputs for a named command can be specified.

In1 stores a set of edges with floating point weights, assumed to have
no duplicates or self-edges. This means that either (Vi,Vj) or
(Vj,Vi) appears, but not both. Also (Vi,Vi) does not appear. The
input is unchanged by this command.

Out1 will store the list of vertices and the distance to each vertex.
If the specified N > 1, then this will be the SSSP result for only the
last source vertex randomly selected.

**Related commands:** none

**(Plimpton)** Plimpton and Devine, "MapReduce in MPI for Large-Scale
Graph Algorithms", to appear in Parallel Computing (2011).