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traverse.go
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traverse.go
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// Copyright ©2015 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 traverse provides basic graph traversal primitives.
package traverse
import (
"golang.org/x/tools/container/intsets"
"k8s.io/kubernetes/third_party/forked/gonum/graph"
"k8s.io/kubernetes/third_party/forked/gonum/graph/internal/linear"
)
// BreadthFirst implements stateful breadth-first graph traversal.
type BreadthFirst struct {
EdgeFilter func(graph.Edge) bool
Visit func(u, v graph.Node)
queue linear.NodeQueue
visited *intsets.Sparse
}
// Walk performs a breadth-first traversal of the graph g starting from the given node,
// depending on the the EdgeFilter field and the until parameter if they are non-nil. The
// traversal follows edges for which EdgeFilter(edge) is true and returns the first node
// for which until(node, depth) is true. During the traversal, if the Visit field is
// non-nil, it is called with the nodes joined by each followed edge.
func (b *BreadthFirst) Walk(g graph.Graph, from graph.Node, until func(n graph.Node, d int) bool) graph.Node {
if b.visited == nil {
b.visited = &intsets.Sparse{}
}
b.queue.Enqueue(from)
b.visited.Insert(from.ID())
var (
depth int
children int
untilNext = 1
)
for b.queue.Len() > 0 {
t := b.queue.Dequeue()
if until != nil && until(t, depth) {
return t
}
for _, n := range g.From(t) {
if b.EdgeFilter != nil && !b.EdgeFilter(g.Edge(t, n)) {
continue
}
if b.visited.Has(n.ID()) {
continue
}
if b.Visit != nil {
b.Visit(t, n)
}
b.visited.Insert(n.ID())
children++
b.queue.Enqueue(n)
}
if untilNext--; untilNext == 0 {
depth++
untilNext = children
children = 0
}
}
return nil
}
// WalkAll calls Walk for each unvisited node of the graph g using edges independent
// of their direction. The functions before and after are called prior to commencing
// and after completing each walk if they are non-nil respectively. The function
// during is called on each node as it is traversed.
func (b *BreadthFirst) WalkAll(g graph.Undirected, before, after func(), during func(graph.Node)) {
b.Reset()
for _, from := range g.Nodes() {
if b.Visited(from) {
continue
}
if before != nil {
before()
}
b.Walk(g, from, func(n graph.Node, _ int) bool {
if during != nil {
during(n)
}
return false
})
if after != nil {
after()
}
}
}
// Visited returned whether the node n was visited during a traverse.
func (b *BreadthFirst) Visited(n graph.Node) bool {
return b.visited != nil && b.visited.Has(n.ID())
}
// Reset resets the state of the traverser for reuse.
func (b *BreadthFirst) Reset() {
b.queue.Reset()
if b.visited != nil {
b.visited.Clear()
}
}
// DepthFirst implements stateful depth-first graph traversal.
type DepthFirst struct {
EdgeFilter func(graph.Edge) bool
Visit func(u, v graph.Node)
stack linear.NodeStack
visited *intsets.Sparse
}
// Walk performs a depth-first traversal of the graph g starting from the given node,
// depending on the the EdgeFilter field and the until parameter if they are non-nil. The
// traversal follows edges for which EdgeFilter(edge) is true and returns the first node
// for which until(node) is true. During the traversal, if the Visit field is non-nil, it
// is called with the nodes joined by each followed edge.
func (d *DepthFirst) Walk(g graph.Graph, from graph.Node, until func(graph.Node) bool) graph.Node {
if d.visited == nil {
d.visited = &intsets.Sparse{}
}
d.stack.Push(from)
d.visited.Insert(from.ID())
for d.stack.Len() > 0 {
t := d.stack.Pop()
if until != nil && until(t) {
return t
}
for _, n := range g.From(t) {
if d.EdgeFilter != nil && !d.EdgeFilter(g.Edge(t, n)) {
continue
}
if d.visited.Has(n.ID()) {
continue
}
if d.Visit != nil {
d.Visit(t, n)
}
d.visited.Insert(n.ID())
d.stack.Push(n)
}
}
return nil
}
// WalkAll calls Walk for each unvisited node of the graph g using edges independent
// of their direction. The functions before and after are called prior to commencing
// and after completing each walk if they are non-nil respectively. The function
// during is called on each node as it is traversed.
func (d *DepthFirst) WalkAll(g graph.Undirected, before, after func(), during func(graph.Node)) {
d.Reset()
for _, from := range g.Nodes() {
if d.Visited(from) {
continue
}
if before != nil {
before()
}
d.Walk(g, from, func(n graph.Node) bool {
if during != nil {
during(n)
}
return false
})
if after != nil {
after()
}
}
}
// Visited returned whether the node n was visited during a traverse.
func (d *DepthFirst) Visited(n graph.Node) bool {
return d.visited != nil && d.visited.Has(n.ID())
}
// Reset resets the state of the traverser for reuse.
func (d *DepthFirst) Reset() {
d.stack = d.stack[:0]
if d.visited != nil {
d.visited.Clear()
}
}