NAME

       dijkstra - single-source distance filter

SYNOPSIS

       dijkstra [ -adp?  ] [ sourcenode file ]

DESCRIPTION

       dijkstra  reads  a  stream of graphs and for each computes the distance of every node from
       sourcenode.  Edge length is given in the len attribute, and the default is  1.   The  dist
       attribute  of  every node is set to its distance from sourcenode.  If the -p flag is used,
       the prev attribute of each node reachable from sourcenode  is  set  to  the  name  of  the
       previous  node on a shortest path.  The graph attribute maxdist is set to the maximum dist
       of all nodes in the graph.

       If the -d flag is used, the graph is treated as directed and only forward edges are used.

       By default, if the graph is disconnected, the dist attribute  of  nodes  unreachable  from
       sourcenode are left untouched, and maxdist is set to the maximum of any previous value and
       the largest distance recorded in this run. On the other hand, if the -a flag is used,  the
       dist  attribute of an unreachable node is assigned a very large value, and maxdist records
       the maximum distance found in the component containing sourcenode.

       Any number of sourcenode file pairs may be given.  If the last file is missing,  stdin  is
       used.  All output is written to stdout.

       In  a typical application, dist and maxdist can drive a downstream calculation of color or
       some other attribute.

SEE ALSO

       gvpr(1), gvcolor(1), libgraph(3)

                                          21 March 2001                               DIJKSTRA(1)