Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

graph/path: Improve performance of YenKShortestPaths #2004

Open
wants to merge 2 commits into
base: master
Choose a base branch
from
Open

graph/path: Improve performance of YenKShortestPaths #2004

Show file tree
Hide file tree
Changes from 1 commit
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
7649851
graph/path: add single-pair shortest path variant
BarrensZeppelin Nov 27, 2024
f112007
graph/path: re-use test setup for `DijkstraFromTo` tests
BarrensZeppelin Dec 2, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
Prev Previous commit
graph/path: re-use test setup for DijkstraFromTo tests 
Also rename `v` parameter to `t`.
  • Loading branch information
@BarrensZeppelin
BarrensZeppelin committed Dec 2, 2024
commit f11200704a1a98a0ffd87d8c54976d6e94300b69
24 changes: 12 additions & 12 deletions graph/path/dijkstra.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -23,27 +23,27 @@ func DijkstraFrom(u graph.Node, g traverse.Graph) Shortest {
return dijkstraFrom(u, nil, g)
}

// DijkstraFromTo returns a shortest path from u to v in the graph g. The
// result is equivalent to DijkstraFrom(u, g).To(v), but DijkstraFromTo can be
// more efficient, as it can terminate early if v is reached. If the graph does
// not implement Weighted, UniformCost is used. DijkstraFromTo will panic if g
// has a u-reachable negative edge weight that is discovered before reaching v.
// DijkstraFromTo returns a shortest path from u to t in the graph g. The
// result is equivalent to DijkstraFrom(u, g).To(t.ID()), but DijkstraFromTo
// can be more efficient, as it can terminate early if t is reached. If the
// graph does not implement Weighted, UniformCost is used. DijkstraFromTo will
// panic if g has a u-reachable negative edge weight that is discovered before
// reaching t.
//
// The time complexity of DijkstraFromTo is O(|E|.log|V|).
func DijkstraFromTo(u graph.Node, v graph.Node, g traverse.Graph) (path []graph.Node, weight float64) {
func DijkstraFromTo(u, t graph.Node, g traverse.Graph) (path []graph.Node, weight float64) {
// An implementation of Bidirectional Dijkstra's algorithm could be even
// more efficient, but it requires a transposed (or undirected) graph.
if v == nil {
if t == nil {
panic("dijkstra: nil target node")
}
return dijkstraFrom(u, v, g).To(v.ID())
return dijkstraFrom(u, t, g).To(t.ID())
}

// Shared implementation of DijkstraFrom and DijkstraFromTo.
func dijkstraFrom(u, target graph.Node, g traverse.Graph) Shortest {
func dijkstraFrom(u, t graph.Node, g traverse.Graph) Shortest {
var path Shortest
// Use the incremental version when a target is provided
if h, ok := g.(graph.Graph); target == nil && ok {
if h, ok := g.(graph.Graph); t == nil && ok {
if h.Node(u.ID()) == nil {
return Shortest{from: u}
}
Expand Down Expand Up @@ -80,7 +80,7 @@ func dijkstraFrom(u, target graph.Node, g traverse.Graph) Shortest {
continue
}
mnid := mid.node.ID()
if target != nil && mnid == target.ID() {
if t != nil && mnid == t.ID() {
break
}
to := g.From(mnid)
Expand Down
78 changes: 27 additions & 51 deletions graph/path/dijkstra_test.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -24,35 +24,14 @@ func TestDijkstraFrom(t *testing.T) {
g.SetWeightedEdge(e)
}

checkPath := func(typ string, p []graph.Node, weight float64) {
if weight != test.Weight {
t.Errorf("%q %s: unexpected weight from To: got:%f want:%f",
test.Name, typ, weight, test.Weight)
}

var got []int64
for _, n := range p {
got = append(got, n.ID())
}
ok := len(got) == 0 && len(test.WantPaths) == 0
for _, sp := range test.WantPaths {
if reflect.DeepEqual(got, sp) {
ok = true
break
}
}
if !ok {
t.Errorf("%q %s: unexpected shortest path:\ngot: %v\nwant from:%v",
test.Name, typ, p, test.WantPaths)
}
}

for _, tg := range []struct {
typ string
g traverse.Graph
t graph.Node
}{
{"complete", g.(graph.Graph)},
{"incremental", incremental{g.(graph.Weighted)}},
{"complete", g.(graph.Graph), nil},
{"incremental", incremental{g.(graph.Weighted)}, nil},
{"single-destination", g.(graph.Graph), test.Query.To()},
} {
var (
pt Shortest
Expand All @@ -63,13 +42,13 @@ func TestDijkstraFrom(t *testing.T) {
defer func() {
panicked = recover() != nil
}()
pt = DijkstraFrom(test.Query.From(), tg.g)
pt = dijkstraFrom(test.Query.From(), tg.t, tg.g)
}()
if panicked || test.HasNegativeWeight {
if !test.HasNegativeWeight {
t.Errorf("%q %s: unexpected panic", test.Name, tg.typ)
}
if !panicked {
if !panicked && tg.t == nil {
t.Errorf("%q %s: expected panic for negative edge weight", test.Name, tg.typ)
}
continue
Expand All @@ -79,41 +58,38 @@ func TestDijkstraFrom(t *testing.T) {
t.Fatalf("%q %s: unexpected from node ID: got:%d want:%d", test.Name, tg.typ, pt.From().ID(), test.Query.From().ID())
}

p, weight := pt.To(test.Query.To().ID())
if weight != test.Weight {
t.Errorf("%q %s: unexpected weight from To: got:%f want:%f",
test.Name, tg.typ, weight, test.Weight)
}
if weight := pt.WeightTo(test.Query.To().ID()); weight != test.Weight {
t.Errorf("%q %s: unexpected weight from Weight: got:%f want:%f",
t.Errorf("%q %s: unexpected weight from WeightTo: got:%f want:%f",
test.Name, tg.typ, weight, test.Weight)
}

p, weight := pt.To(test.Query.To().ID())
checkPath(tg.typ, p, weight)
var got []int64
for _, n := range p {
got = append(got, n.ID())
}
ok := len(got) == 0 && len(test.WantPaths) == 0
for _, sp := range test.WantPaths {
if reflect.DeepEqual(got, sp) {
ok = true
break
}
}
if !ok {
t.Errorf("%q %s: unexpected shortest path:\ngot: %v\nwant from:%v",
test.Name, tg.typ, p, test.WantPaths)
}

np, weight := pt.To(test.NoPathFor.To().ID())
if pt.From().ID() == test.NoPathFor.From().ID() && (np != nil || !math.IsInf(weight, 1)) {
t.Errorf("%q %s: unexpected path:\ngot: path=%v weight=%f\nwant:path=<nil> weight=+Inf",
test.Name, tg.typ, np, weight)
}
}

// Test the single-destination variant.
var (
p []graph.Node
weight float64
panicked bool
)
func() {
defer func() {
panicked = recover() != nil
}()
p, weight = DijkstraFromTo(test.Query.From(), test.Query.To(), g.(graph.Graph))
}()
if panicked || test.HasNegativeWeight {
if !test.HasNegativeWeight {
t.Errorf("%q: unexpected panic", test.Name)
}
continue
}

checkPath("from-to", p, weight)
}
}

Expand Down
Loading