func TestNavigableSmallWorldUndirected(t *testing.T) {
	for p := 1; p < 5; p++ {
		for q := 0; q < 10; q++ {
			for r := 0.5; r < 10; r++ {
				for _, dims := range smallWorldDimensionParameters {
					g := &gnUndirected{UndirectedBuilder: simple.NewUndirectedGraph(0, math.Inf(1))}
					err := NavigableSmallWorld(g, dims, p, q, r, nil)
					n := 1
					for _, d := range dims {
						n *= d
					}
					if err != nil {
						t.Fatalf("unexpected error: dims=%v n=%d, p=%d, q=%d, r=%v: %v", dims, n, p, q, r, err)
					}
					if g.addBackwards {
						t.Errorf("edge added with From.ID > To.ID: dims=%v n=%d, p=%d, q=%d, r=%v", dims, n, p, q, r)
					}
					if g.addSelfLoop {
						t.Errorf("unexpected self edge: dims=%v n=%d, p=%d, q=%d, r=%v", dims, n, p, q, r)
					}
					if g.addMultipleEdge {
						t.Errorf("unexpected multiple edge: dims=%v n=%d, p=%d, q=%d, r=%v", dims, n, p, q, r)
					}
				}
			}
		}
	}
}

func TestWalkAll(t *testing.T) {
	for i, test := range walkAllTests {
		g := simple.NewUndirectedGraph(0, math.Inf(1))

		for u, e := range test.g {
			if !g.Has(simple.Node(u)) {
				g.AddNode(simple.Node(u))
			}
			for v := range e {
				if !g.Has(simple.Node(v)) {
					g.AddNode(simple.Node(v))
				}
				g.SetEdge(simple.Edge{F: simple.Node(u), T: simple.Node(v)})
			}
		}
		type walker interface {
			WalkAll(g graph.Undirected, before, after func(), during func(graph.Node))
		}
		for _, w := range []walker{
			&BreadthFirst{},
			&DepthFirst{},
		} {
			var (
				c  []graph.Node
				cc [][]graph.Node
			)
			switch w := w.(type) {
			case *BreadthFirst:
				w.EdgeFilter = test.edge
			case *DepthFirst:
				w.EdgeFilter = test.edge
			default:
				panic(fmt.Sprintf("bad walker type: %T", w))
			}
			during := func(n graph.Node) {
				c = append(c, n)
			}
			after := func() {
				cc = append(cc, []graph.Node(nil))
				cc[len(cc)-1] = append(cc[len(cc)-1], c...)
				c = c[:0]
			}
			w.WalkAll(g, nil, after, during)

			got := make([][]int, len(cc))
			for j, c := range cc {
				ids := make([]int, len(c))
				for k, n := range c {
					ids[k] = n.ID()
				}
				sort.Ints(ids)
				got[j] = ids
			}
			sort.Sort(ordered.BySliceValues(got))
			if !reflect.DeepEqual(got, test.want) {
				t.Errorf("unexpected connected components for test %d using %T:\ngot: %v\nwant:%v", i, w, got, test.want)
			}
		}
	}
}

func TestDepthFirst(t *testing.T) {
	for i, test := range depthFirstTests {
		g := simple.NewUndirectedGraph(0, math.Inf(1))
		for u, e := range test.g {
			// Add nodes that are not defined by an edge.
			if !g.Has(simple.Node(u)) {
				g.AddNode(simple.Node(u))
			}
			for v := range e {
				g.SetEdge(simple.Edge{F: simple.Node(u), T: simple.Node(v)})
			}
		}
		w := DepthFirst{
			EdgeFilter: test.edge,
		}
		var got []int
		final := w.Walk(g, test.from, func(n graph.Node) bool {
			if test.until != nil && test.until(n) {
				return true
			}
			got = append(got, n.ID())
			return false
		})
		if !test.final[final] {
			t.Errorf("unexepected final node for test %d:\ngot:  %v\nwant: %v", i, final, test.final)
		}
		sort.Ints(got)
		if test.want != nil && !reflect.DeepEqual(got, test.want) {
			t.Errorf("unexepected DFS traversed nodes for test %d:\ngot:  %v\nwant: %v", i, got, test.want)
		}
	}
}

func TestCommunityQ(t *testing.T) {
	for _, test := range communityQTests {
		g := simple.NewUndirectedGraph(0, 0)
		for u, e := range test.g {
			// Add nodes that are not defined by an edge.
			if !g.Has(simple.Node(u)) {
				g.AddNode(simple.Node(u))
			}
			for v := range e {
				g.SetEdge(simple.Edge{F: simple.Node(u), T: simple.Node(v), W: 1})
			}
		}
		for _, structure := range test.structures {
			communities := make([][]graph.Node, len(structure.memberships))
			for i, c := range structure.memberships {
				for n := range c {
					communities[i] = append(communities[i], simple.Node(n))
				}
			}
			got := Q(g, communities, structure.resolution)
			if !floats.EqualWithinAbsOrRel(got, structure.want, structure.tol, structure.tol) && math.IsNaN(got) != math.IsNaN(structure.want) {
				for _, c := range communities {
					sort.Sort(ordered.ByID(c))
				}
				t.Errorf("unexpected Q value for %q %v: got: %v want: %v",
					test.name, communities, got, structure.want)
			}
		}
	}
}

func TestBronKerbosch(t *testing.T) {
	for i, test := range bronKerboschTests {
		g := simple.NewUndirectedGraph(0, math.Inf(1))
		for u, e := range test.g {
			// Add nodes that are not defined by an edge.
			if !g.Has(simple.Node(u)) {
				g.AddNode(simple.Node(u))
			}
			for v := range e {
				g.SetEdge(simple.Edge{F: simple.Node(u), T: simple.Node(v)})
			}
		}
		cliques := BronKerbosch(g)
		got := make([][]int, len(cliques))
		for j, c := range cliques {
			ids := make([]int, len(c))
			for k, n := range c {
				ids[k] = n.ID()
			}
			sort.Ints(ids)
			got[j] = ids
		}
		sort.Sort(ordered.BySliceValues(got))
		if !reflect.DeepEqual(got, test.want) {
			t.Errorf("unexpected cliques for test %d:\ngot: %v\nwant:%v", i, got, test.want)
		}
	}
}

func TestConnectedComponents(t *testing.T) {
	for i, test := range connectedComponentTests {
		g := simple.NewUndirectedGraph(0, math.Inf(1))

		for u, e := range test.g {
			if !g.Has(simple.Node(u)) {
				g.AddNode(simple.Node(u))
			}
			for v := range e {
				if !g.Has(simple.Node(v)) {
					g.AddNode(simple.Node(v))
				}
				g.SetEdge(simple.Edge{F: simple.Node(u), T: simple.Node(v)})
			}
		}
		cc := ConnectedComponents(g)
		got := make([][]int, len(cc))
		for j, c := range cc {
			ids := make([]int, len(c))
			for k, n := range c {
				ids[k] = n.ID()
			}
			sort.Ints(ids)
			got[j] = ids
		}
		sort.Sort(ordered.BySliceValues(got))
		if !reflect.DeepEqual(got, test.want) {
			t.Errorf("unexpected connected components for test %d %T:\ngot: %v\nwant:%v", i, g, got, test.want)
		}
	}
}

func TestEdgeBetweenness(t *testing.T) {
	for i, test := range betweennessTests {
		g := simple.NewUndirectedGraph(0, math.Inf(1))
		for u, e := range test.g {
			// Add nodes that are not defined by an edge.
			if !g.Has(simple.Node(u)) {
				g.AddNode(simple.Node(u))
			}
			for v := range e {
				// Weight omitted to show weight-independence.
				g.SetEdge(simple.Edge{F: simple.Node(u), T: simple.Node(v), W: 0})
			}
		}
		got := EdgeBetweenness(g)
		prec := 1 - int(math.Log10(test.wantTol))
	outer:
		for u := range test.g {
			for v := range test.g {
				wantQ, gotOK := got[[2]int{u, v}]
				gotQ, wantOK := test.wantEdges[[2]int{u, v}]
				if gotOK != wantOK {
					t.Errorf("unexpected betweenness result for test %d, edge (%c,%c)", i, u+'A', v+'A')
				}
				if !floats.EqualWithinAbsOrRel(gotQ, wantQ, test.wantTol, test.wantTol) {
					t.Errorf("unexpected betweenness result for test %d:\ngot: %v\nwant:%v",
						i, orderedPairFloats(got, prec), orderedPairFloats(test.wantEdges, prec))
					break outer
				}
			}
		}
	}
}

func TestBetweennessWeighted(t *testing.T) {
	for i, test := range betweennessTests {
		g := simple.NewUndirectedGraph(0, math.Inf(1))
		for u, e := range test.g {
			// Add nodes that are not defined by an edge.
			if !g.Has(simple.Node(u)) {
				g.AddNode(simple.Node(u))
			}
			for v := range e {
				g.SetEdge(simple.Edge{F: simple.Node(u), T: simple.Node(v), W: 1})
			}
		}

		p, ok := path.FloydWarshall(g)
		if !ok {
			t.Errorf("unexpected negative cycle in test %d", i)
			continue
		}

		got := BetweennessWeighted(g, p)
		prec := 1 - int(math.Log10(test.wantTol))
		for n := range test.g {
			gotN, gotOK := got[n]
			wantN, wantOK := test.want[n]
			if gotOK != wantOK {
				t.Errorf("unexpected betweenness existence for test %d, node %c", i, n+'A')
			}
			if !floats.EqualWithinAbsOrRel(gotN, wantN, test.wantTol, test.wantTol) {
				t.Errorf("unexpected betweenness result for test %d:\ngot: %v\nwant:%v",
					i, orderedFloats(got, prec), orderedFloats(test.want, prec))
				break
			}
		}
	}
}

func undirectedEdgeAttrGraphFrom(g []set, attr map[edge][]Attribute) graph.Graph {
	dg := simple.NewUndirectedGraph(0, math.Inf(1))
	for u, e := range g {
		for v := range e {
			dg.SetEdge(attrEdge{from: simple.Node(u), to: simple.Node(v), attr: attr[edge{from: u, to: v}]})
		}
	}
	return dg
}

func undirectedGraphFrom(g []set) graph.Graph {
	dg := simple.NewUndirectedGraph(0, math.Inf(1))
	for u, e := range g {
		for v := range e {
			dg.SetEdge(simple.Edge{F: simple.Node(u), T: simple.Node(v)})
		}
	}
	return dg
}

func TestExhaustiveAStar(t *testing.T) {
	g := simple.NewUndirectedGraph(0, math.Inf(1))
	nodes := []locatedNode{
		{id: 1, x: 0, y: 6},
		{id: 2, x: 1, y: 0},
		{id: 3, x: 8, y: 7},
		{id: 4, x: 16, y: 0},
		{id: 5, x: 17, y: 6},
		{id: 6, x: 9, y: 8},
	}
	for _, n := range nodes {
		g.AddNode(n)
	}

	edges := []weightedEdge{
		{from: g.Node(1), to: g.Node(2), cost: 7},
		{from: g.Node(1), to: g.Node(3), cost: 9},
		{from: g.Node(1), to: g.Node(6), cost: 14},
		{from: g.Node(2), to: g.Node(3), cost: 10},
		{from: g.Node(2), to: g.Node(4), cost: 15},
		{from: g.Node(3), to: g.Node(4), cost: 11},
		{from: g.Node(3), to: g.Node(6), cost: 2},
		{from: g.Node(4), to: g.Node(5), cost: 7},
		{from: g.Node(5), to: g.Node(6), cost: 9},
	}
	for _, e := range edges {
		g.SetEdge(e)
	}

	heuristic := func(u, v graph.Node) float64 {
		lu := u.(locatedNode)
		lv := v.(locatedNode)
		return math.Hypot(lu.x-lv.x, lu.y-lv.y)
	}

	if ok, edge, goal := isMonotonic(g, heuristic); !ok {
		t.Fatalf("non-monotonic heuristic at edge:%v for goal:%v", edge, goal)
	}

	ps := DijkstraAllPaths(g)
	for _, start := range g.Nodes() {
		for _, goal := range g.Nodes() {
			pt, _ := AStar(start, goal, g, heuristic)
			gotPath, gotWeight := pt.To(goal)
			wantPath, wantWeight, _ := ps.Between(start, goal)
			if gotWeight != wantWeight {
				t.Errorf("unexpected path weight from %v to %v result: got:%s want:%s",
					start, goal, gotWeight, wantWeight)
			}
			if !reflect.DeepEqual(gotPath, wantPath) {
				t.Errorf("unexpected path from %v to %v result:\ngot: %v\nwant:%v",
					start, goal, gotPath, wantPath)
			}
		}
	}
}

func undirectedStructuredGraphFrom(c []edge, g ...[]set) graph.Graph {
	s := &structuredGraph{UndirectedGraph: simple.NewUndirectedGraph(0, math.Inf(1))}
	var base int
	for i, sg := range g {
		sub := simple.NewUndirectedGraph(0, math.Inf(1))
		for u, e := range sg {
			for v := range e {
				ce := simple.Edge{F: simple.Node(u + base), T: simple.Node(v + base)}
				sub.SetEdge(ce)
			}
		}
		s.sub = append(s.sub, namedGraph{id: i, Graph: sub})
		base += len(sg)
	}
	for _, e := range c {
		s.SetEdge(simple.Edge{F: simple.Node(e.from), T: simple.Node(e.to)})
	}
	return s
}

func undirectedNamedIDGraphFrom(g []set) graph.Graph {
	dg := simple.NewUndirectedGraph(0, math.Inf(1))
	for u, e := range g {
		nu := namedNode{id: u, name: alpha[u : u+1]}
		for v := range e {
			nv := namedNode{id: v, name: alpha[v : v+1]}
			dg.SetEdge(simple.Edge{F: nu, T: nv})
		}
	}
	return dg
}

func undirectedSubGraphFrom(g []set, s map[int][]set) graph.Graph {
	var base int
	subs := make(map[int]subGraph)
	for i, sg := range s {
		sub := simple.NewUndirectedGraph(0, math.Inf(1))
		for u, e := range sg {
			for v := range e {
				ce := simple.Edge{F: simple.Node(u + base), T: simple.Node(v + base)}
				sub.SetEdge(ce)
			}
		}
		subs[i] = subGraph{id: i, Graph: sub}
		base += len(sg)
	}

	dg := simple.NewUndirectedGraph(0, math.Inf(1))
	for u, e := range g {
		var nu graph.Node
		if sg, ok := subs[u]; ok {
			sg.id += base
			nu = sg
		} else {
			nu = simple.Node(u + base)
		}
		for v := range e {
			var nv graph.Node
			if sg, ok := subs[v]; ok {
				sg.id += base
				nv = sg
			} else {
				nv = simple.Node(v + base)
			}
			dg.SetEdge(simple.Edge{F: nu, T: nv})
		}
	}
	return dg
}

func TestReduceQConsistency(t *testing.T) {
tests:
	for _, test := range communityQTests {
		g := simple.NewUndirectedGraph(0, 0)
		for u, e := range test.g {
			// Add nodes that are not defined by an edge.
			if !g.Has(simple.Node(u)) {
				g.AddNode(simple.Node(u))
			}
			for v := range e {
				g.SetEdge(simple.Edge{F: simple.Node(u), T: simple.Node(v), W: 1})
			}
		}

		for _, structure := range test.structures {
			if math.IsNaN(structure.want) {
				continue tests
			}

			communities := make([][]graph.Node, len(structure.memberships))
			for i, c := range structure.memberships {
				for n := range c {
					communities[i] = append(communities[i], simple.Node(n))
				}
				sort.Sort(ordered.ByID(communities[i]))
			}

			gQ := Q(g, communities, structure.resolution)
			gQnull := Q(g, nil, 1)

			cg0 := reduce(g, nil)
			cg0Qnull := Q(cg0, cg0.Structure(), 1)
			if !floats.EqualWithinAbsOrRel(gQnull, cg0Qnull, structure.tol, structure.tol) {
				t.Errorf("disgagreement between null Q from method: %v and function: %v", cg0Qnull, gQnull)
			}
			cg0Q := Q(cg0, communities, structure.resolution)
			if !floats.EqualWithinAbsOrRel(gQ, cg0Q, structure.tol, structure.tol) {
				t.Errorf("unexpected Q result after initial conversion: got: %v want :%v", gQ, cg0Q)
			}

			cg1 := reduce(cg0, communities)
			cg1Q := Q(cg1, cg1.Structure(), structure.resolution)
			if !floats.EqualWithinAbsOrRel(gQ, cg1Q, structure.tol, structure.tol) {
				t.Errorf("unexpected Q result after initial condensation: got: %v want :%v", gQ, cg1Q)
			}
		}
	}
}

func undirectedNamedIDNodeAttrGraphFrom(g []set, attr [][]Attribute) graph.Graph {
	dg := simple.NewUndirectedGraph(0, math.Inf(1))
	for u, e := range g {
		var at []Attribute
		if u < len(attr) {
			at = attr[u]
		}
		nu := namedAttrNode{id: u, name: alpha[u : u+1], attr: at}
		for v := range e {
			if v < len(attr) {
				at = attr[v]
			}
			nv := namedAttrNode{id: v, name: alpha[v : v+1], attr: at}
			dg.SetEdge(simple.Edge{F: nu, T: nv})
		}
	}
	return dg
}

func TestNonContiguous(t *testing.T) {
	g := simple.NewUndirectedGraph(0, 0)
	for _, e := range []simple.Edge{
		{F: simple.Node(0), T: simple.Node(1), W: 1},
		{F: simple.Node(4), T: simple.Node(5), W: 1},
	} {
		g.SetEdge(e)
	}

	func() {
		defer func() {
			r := recover()
			if r != nil {
				t.Error("unexpected panic with non-contiguous ID range")
			}
		}()
		Louvain(g, 1, nil)
	}()
}

func TestGnpUndirected(t *testing.T) {
	for n := 2; n <= 20; n++ {
		for p := 0.; p <= 1; p += 0.1 {
			g := &gnUndirected{UndirectedBuilder: simple.NewUndirectedGraph(0, math.Inf(1))}
			err := Gnp(g, n, p, nil)
			if err != nil {
				t.Fatalf("unexpected error: n=%d, p=%v: %v", n, p, err)
			}
			if g.addBackwards {
				t.Errorf("edge added with From.ID > To.ID: n=%d, p=%v", n, p)
			}
			if g.addSelfLoop {
				t.Errorf("unexpected self edge: n=%d, p=%v", n, p)
			}
			if g.addMultipleEdge {
				t.Errorf("unexpected multiple edge: n=%d, p=%v", n, p)
			}
		}
	}
}

func TestPreferentialAttachment(t *testing.T) {
	for n := 2; n <= 20; n++ {
		for m := 0; m < n; m++ {
			g := &gnUndirected{UndirectedBuilder: simple.NewUndirectedGraph(0, math.Inf(1))}
			err := PreferentialAttachment(g, n, m, nil)
			if err != nil {
				t.Fatalf("unexpected error: n=%d, m=%d: %v", n, m, err)
			}
			if g.addBackwards {
				t.Errorf("edge added with From.ID > To.ID: n=%d, m=%d", n, m)
			}
			if g.addSelfLoop {
				t.Errorf("unexpected self edge: n=%d, m=%d", n, m)
			}
			if g.addMultipleEdge {
				t.Errorf("unexpected multiple edge: n=%d, m=%d", n, m)
			}
		}
	}
}

func undirectedPortedAttrGraphFrom(g []set, attr [][]Attribute, ports map[edge]portedEdge) graph.Graph {
	dg := simple.NewUndirectedGraph(0, math.Inf(1))
	for u, e := range g {
		var at []Attribute
		if u < len(attr) {
			at = attr[u]
		}
		nu := attrNode{id: u, attr: at}
		for v := range e {
			if v < len(attr) {
				at = attr[v]
			}
			pe := ports[edge{from: u, to: v}]
			pe.from = nu
			pe.to = attrNode{id: v, attr: at}
			dg.SetEdge(pe)
		}
	}
	return dg
}