v.net.allpairs computes the shortest path between each select node and all other nodes.
NOTES
An attribute table is created and linked to layer. The table contains three columns: cat, to_cat, cost. Each entry denotes the cost of the shortest path from cat to to_cat. If the cost is negative then no path exists. If points are specified by cats, layer or where parameters then the table is filled only for the selected points. In other words, cat columns contains only selected points but the distances are computed and updated for all other nodes.
If flag -a is set then new points are added on nodes without nodes. These points have the largest categorie. Precisely, category of each new point is larger than any of the old categories. If the flag is not set then no new points are created and hence the attribute table stores the costs only between the points already present in the input. Output consists of all points mentioned in either of the columns.
If abcolumn is not given then then the same costs are used for forward and backward arcs.
EXAMPLES
Find shortest path from each intersection with pedestrian crossing to every other point using SHAPE_LEN for the cost of traversing the arcs in both directions.