Add benchmarks

Author: Stefan Nilsson

weak.go

@@ -45,8 +45,9 @@ func components(g Iterator) (sets disjointSets, count int) {
 	return
 }
 
-// Union-find with path compression performs any sequence of
-// m ≥ n find and n – 1 union operations in O(m log n) time.
+// Union-find with path compression performs any sequence of m ≥ n find
+// and n – 1 union operations in O(m log n) time. Union by rank doesn't
+// seem to improve performance here.
 type disjointSets []int
 
 func makeSingletons(n int) disjointSets {

weak_test.go

@@ -1,6 +1,7 @@
 package graph
 
 import (
+	"math/rand"
 	"testing"
 )
 
@@ -50,3 +51,29 @@ func TestComponents(t *testing.T) {
 		t.Errorf("Connected %s", mess)
 	}
 }
+
+func BenchmarkConnected(b *testing.B) {
+	n := 1000
+	b.StopTimer()
+	g := New(n)
+	for i := 0; i < n; i++ {
+		g.AddBoth(rand.Intn(n), rand.Intn(n))
+	}
+	b.StartTimer()
+	for i := 0; i < b.N; i++ {
+		_ = Connected(g)
+	}
+}
+
+func BenchmarkComponents(b *testing.B) {
+	n := 1000
+	b.StopTimer()
+	g := New(n)
+	for i := 0; i < n; i++ {
+		g.AddBoth(rand.Intn(n), rand.Intn(n))
+	}
+	b.StartTimer()
+	for i := 0; i < b.N; i++ {
+		_ = Components(g)
+	}
+}