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// Copyright ©2014 The Gonum Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package simple
import (
"fmt"
"gonum.org/v1/gonum/graph"
"gonum.org/v1/gonum/graph/internal/uid"
"gonum.org/v1/gonum/graph/iterator"
)
var (
wdg *WeightedDirectedGraph
_ graph.Graph = wdg
_ graph.Weighted = wdg
_ graph.Directed = wdg
_ graph.WeightedDirected = wdg
_ graph.NodeAdder = wdg
_ graph.NodeRemover = wdg
_ graph.WeightedEdgeAdder = wdg
_ graph.EdgeRemover = wdg
)
// WeightedDirectedGraph implements a generalized weighted directed graph.
type WeightedDirectedGraph struct {
nodes map[int64]graph.Node
from map[int64]map[int64]graph.WeightedEdge
to map[int64]map[int64]graph.WeightedEdge
self, absent float64
nodeIDs uid.Set
}
// NewWeightedDirectedGraph returns a WeightedDirectedGraph with the specified self and absent
// edge weight values.
func NewWeightedDirectedGraph(self, absent float64) *WeightedDirectedGraph {
return &WeightedDirectedGraph{
nodes: make(map[int64]graph.Node),
from: make(map[int64]map[int64]graph.WeightedEdge),
to: make(map[int64]map[int64]graph.WeightedEdge),
self: self,
absent: absent,
nodeIDs: uid.NewSet(),
}
}
// AddNode adds n to the graph. It panics if the added node ID matches an existing node ID.
func (g *WeightedDirectedGraph) AddNode(n graph.Node) {
if _, exists := g.nodes[n.ID()]; exists {
panic(fmt.Sprintf("simple: node ID collision: %d", n.ID()))
}
g.nodes[n.ID()] = n
g.from[n.ID()] = make(map[int64]graph.WeightedEdge)
g.to[n.ID()] = make(map[int64]graph.WeightedEdge)
g.nodeIDs.Use(n.ID())
}
// Edge returns the edge from u to v if such an edge exists and nil otherwise.
// The node v must be directly reachable from u as defined by the From method.
func (g *WeightedDirectedGraph) Edge(uid, vid int64) graph.Edge {
return g.WeightedEdge(uid, vid)
}
// Edges returns all the edges in the graph.
func (g *WeightedDirectedGraph) Edges() graph.Edges {
var edges []graph.Edge
for _, u := range g.nodes {
for _, e := range g.from[u.ID()] {
edges = append(edges, e)
}
}
if len(edges) == 0 {
return graph.Empty
}
return iterator.NewOrderedEdges(edges)
}
// From returns all nodes in g that can be reached directly from n.
func (g *WeightedDirectedGraph) From(id int64) graph.Nodes {
if _, ok := g.from[id]; !ok {
return graph.Empty
}
from := make([]graph.Node, len(g.from[id]))
i := 0
for vid := range g.from[id] {
from[i] = g.nodes[vid]
i++
}
if len(from) == 0 {
return graph.Empty
}
return iterator.NewOrderedNodes(from)
}
// HasEdgeBetween returns whether an edge exists between nodes x and y without
// considering direction.
func (g *WeightedDirectedGraph) HasEdgeBetween(xid, yid int64) bool {
if _, ok := g.from[xid][yid]; ok {
return true
}
_, ok := g.from[yid][xid]
return ok
}
// HasEdgeFromTo returns whether an edge exists in the graph from u to v.
func (g *WeightedDirectedGraph) HasEdgeFromTo(uid, vid int64) bool {
if _, ok := g.from[uid][vid]; !ok {
return false
}
return true
}
// NewNode returns a new unique Node to be added to g. The Node's ID does
// not become valid in g until the Node is added to g.
func (g *WeightedDirectedGraph) NewNode() graph.Node {
if len(g.nodes) == 0 {
return Node(0)
}
if int64(len(g.nodes)) == uid.Max {
panic("simple: cannot allocate node: no slot")
}
return Node(g.nodeIDs.NewID())
}
// NewWeightedEdge returns a new weighted edge from the source to the destination node.
func (g *WeightedDirectedGraph) NewWeightedEdge(from, to graph.Node, weight float64) graph.WeightedEdge {
return &WeightedEdge{F: from, T: to, W: weight}
}
// Node returns the node with the given ID if it exists in the graph,
// and nil otherwise.
func (g *WeightedDirectedGraph) Node(id int64) graph.Node {
return g.nodes[id]
}
// Nodes returns all the nodes in the graph.
func (g *WeightedDirectedGraph) Nodes() graph.Nodes {
if len(g.from) == 0 {
return graph.Empty
}
nodes := make([]graph.Node, len(g.nodes))
i := 0
for _, n := range g.nodes {
nodes[i] = n
i++
}
return iterator.NewOrderedNodes(nodes)
}
// RemoveEdge removes the edge with the given end point IDs from the graph, leaving the terminal
// nodes. If the edge does not exist it is a no-op.
func (g *WeightedDirectedGraph) RemoveEdge(fid, tid int64) {
if _, ok := g.nodes[fid]; !ok {
return
}
if _, ok := g.nodes[tid]; !ok {
return
}
delete(g.from[fid], tid)
delete(g.to[tid], fid)
}
// RemoveNode removes the node with the given ID from the graph, as well as any edges attached
// to it. If the node is not in the graph it is a no-op.
func (g *WeightedDirectedGraph) RemoveNode(id int64) {
if _, ok := g.nodes[id]; !ok {
return
}
delete(g.nodes, id)
for from := range g.from[id] {
delete(g.to[from], id)
}
delete(g.from, id)
for to := range g.to[id] {
delete(g.from[to], id)
}
delete(g.to, id)
g.nodeIDs.Release(id)
}
// SetWeightedEdge adds a weighted edge from one node to another. If the nodes do not exist, they are added
// and are set to the nodes of the edge otherwise.
// It will panic if the IDs of the e.From and e.To are equal.
func (g *WeightedDirectedGraph) SetWeightedEdge(e graph.WeightedEdge) {
var (
from = e.From()
fid = from.ID()
to = e.To()
tid = to.ID()
)
if fid == tid {
panic("simple: adding self edge")
}
if _, ok := g.nodes[fid]; !ok {
g.AddNode(from)
} else {
g.nodes[fid] = from
}
if _, ok := g.nodes[tid]; !ok {
g.AddNode(to)
} else {
g.nodes[tid] = to
}
g.from[fid][tid] = e
g.to[tid][fid] = e
}
// To returns all nodes in g that can reach directly to n.
func (g *WeightedDirectedGraph) To(id int64) graph.Nodes {
if _, ok := g.from[id]; !ok {
return graph.Empty
}
to := make([]graph.Node, len(g.to[id]))
i := 0
for uid := range g.to[id] {
to[i] = g.nodes[uid]
i++
}
if len(to) == 0 {
return graph.Empty
}
return iterator.NewOrderedNodes(to)
}
// Weight returns the weight for the edge between x and y if Edge(x, y) returns a non-nil Edge.
// If x and y are the same node or there is no joining edge between the two nodes the weight
// value returned is either the graph's absent or self value. Weight returns true if an edge
// exists between x and y or if x and y have the same ID, false otherwise.
func (g *WeightedDirectedGraph) Weight(xid, yid int64) (w float64, ok bool) {
if xid == yid {
return g.self, true
}
if to, ok := g.from[xid]; ok {
if e, ok := to[yid]; ok {
return e.Weight(), true
}
}
return g.absent, false
}
// WeightedEdge returns the weighted edge from u to v if such an edge exists and nil otherwise.
// The node v must be directly reachable from u as defined by the From method.
func (g *WeightedDirectedGraph) WeightedEdge(uid, vid int64) graph.WeightedEdge {
edge, ok := g.from[uid][vid]
if !ok {
return nil
}
return edge
}
// WeightedEdges returns all the weighted edges in the graph.
func (g *WeightedDirectedGraph) WeightedEdges() graph.WeightedEdges {
var edges []graph.WeightedEdge
for _, u := range g.nodes {
for _, e := range g.from[u.ID()] {
edges = append(edges, e)
}
}
if len(edges) == 0 {
return graph.Empty
}
return iterator.NewOrderedWeightedEdges(edges)
}