remove empty layer after delete or update value (#11)

1. don't panic when update data or search and and remove empty layer after
2. add new search function return distance

Author: Asutorufa

go.mod

@@ -2,20 +2,19 @@ module github.com/coder/hnsw
 
 go 1.21.4
 
-require github.com/stretchr/testify v1.9.0
-
-require github.com/google/renameio v1.0.1
-
 require (
-	github.com/chewxy/math32 v1.10.1 // indirect
-	github.com/viterin/partial v1.1.0 // indirect
-	github.com/viterin/vek v0.4.2 // indirect
-	golang.org/x/sys v0.11.0 // indirect
+	github.com/google/renameio v1.0.1
+	github.com/stretchr/testify v1.9.0
 )
 
 require (
+	github.com/chewxy/math32 v1.10.1 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/kr/text v0.2.0 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/viterin/partial v1.1.0 // indirect
+	github.com/viterin/vek v0.4.2
 	golang.org/x/exp v0.0.0-20240506185415-9bf2ced13842
+	golang.org/x/sys v0.11.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -1,9 +1,14 @@
 github.com/chewxy/math32 v1.10.1 h1:LFpeY0SLJXeaiej/eIp2L40VYfscTvKh/FSEZ68uMkU=
 github.com/chewxy/math32 v1.10.1/go.mod h1:dOB2rcuFrCn6UHrze36WSLVPKtzPMRAQvBvUwkSsLqs=
+github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/google/renameio v1.0.1 h1:Lh/jXZmvZxb0BBeSY5VKEfidcbcbenKjZFzM/q0fSeU=
 github.com/google/renameio v1.0.1/go.mod h1:t/HQoYBZSsWSNK35C6CO/TpPLDVWvxOHboWUAweKUpk=
+github.com/kr/pretty v0.1.0 h1:L/CwN0zerZDmRFUapSPitk6f+Q3+0za1rQkzVuMiMFI=
+github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
+github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
+github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
@@ -16,7 +21,8 @@ golang.org/x/exp v0.0.0-20240506185415-9bf2ced13842 h1:vr/HnozRka3pE4EsMEg1lgkXJ
 golang.org/x/exp v0.0.0-20240506185415-9bf2ced13842/go.mod h1:XtvwrStGgqGPLc4cjQfWqZHG1YFdYs6swckp8vpsjnc=
 golang.org/x/sys v0.11.0 h1:eG7RXZHdqOJ1i+0lgLgCpSXAp6M3LYlAo6osgSi0xOM=
 golang.org/x/sys v0.11.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 h1:qIbj1fsPNlZgppZ+VLlY7N33q108Sa+fhmuc+sWQYwY=
+gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

graph.go

@@ -402,13 +402,35 @@ func (g *Graph[K]) Add(nodes ...Node[K]) {
 
 		// Invariant check: the node should have been added to the graph.
 		if g.Len() != preLen+1 {
-			panic("node not added")
+			if len(g.layers) > 0 && g.layers[len(g.layers)-1].entry() == nil {
+				g.layers = g.layers[:len(g.layers)-1]
+			}
 		}
 	}
 }
 
 // Search finds the k nearest neighbors from the target node.
 func (h *Graph[K]) Search(near Vector, k int) []Node[K] {
+	sr := h.search(near, k)
+	out := make([]Node[K], len(sr))
+	for i, node := range sr {
+		out[i] = node.Node
+	}
+	return out
+}
+
+// SearchWithDistance finds the k nearest neighbors from the target node
+// and returns the distance.
+func (h *Graph[K]) SearchWithDistance(near Vector, k int) []SearchResult[K] {
+	return h.search(near, k)
+}
+
+type SearchResult[T cmp.Ordered] struct {
+	Node[T]
+	Distance float32
+}
+
+func (h *Graph[K]) search(near Vector, k int) []SearchResult[K] {
 	h.assertDims(near)
 	if len(h.layers) == 0 {
 		return nil
@@ -434,10 +456,13 @@ func (h *Graph[K]) Search(near Vector, k int) []Node[K] {
 		}
 
 		nodes := searchPoint.search(k, efSearch, near, h.Distance)
-		out := make([]Node[K], 0, len(nodes))
+		out := make([]SearchResult[K], 0, len(nodes))
 
 		for _, node := range nodes {
-			out = append(out, node.node.Node)
+			out = append(out, SearchResult[K]{
+				Node:     node.node.Node,
+				Distance: node.dist,
+			})
 		}
 
 		return out
@@ -462,17 +487,33 @@ func (h *Graph[K]) Delete(key K) bool {
 		return false
 	}
 
+	var deleteLayer = map[int]struct{}{}
 	var deleted bool
-	for _, layer := range h.layers {
+	for i, layer := range h.layers {
 		node, ok := layer.nodes[key]
 		if !ok {
 			continue
 		}
 		delete(layer.nodes, key)
+		if len(layer.nodes) == 0 {
+			deleteLayer[i] = struct{}{}
+		}
 		node.isolate(h.M)
 		deleted = true
 	}
 
+	if len(deleteLayer) > 0 {
+		var newLayers = make([]*layer[K], 0, len(h.layers)-len(deleteLayer))
+		for i, layer := range h.layers {
+			if _, ok := deleteLayer[i]; ok {
+				continue
+			}
+			newLayers = append(newLayers, layer)
+		}
+
+		h.layers = newLayers
+	}
+
 	return deleted
 }
 

graph_test.go

@@ -248,3 +248,14 @@ func TestGraph_DefaultCosine(t *testing.T) {
 		neighbors,
 	)
 }
+
+func TestGraph_RemoveAllNodes(t *testing.T) {
+	var vec = []float32{1}
+
+	for i := 0; i < 10; i++ {
+		g := NewGraph[int]()
+		g.Add(MakeNode(1, vec))
+		g.Delete(1)
+		g.Add(MakeNode(1, vec))
+	}
+}