summaryrefslogtreecommitdiffstats
path: root/src/cmd/compile/internal/pgo/graph.go
diff options
context:
space:
mode:
Diffstat (limited to 'src/cmd/compile/internal/pgo/graph.go')
-rw-r--r--src/cmd/compile/internal/pgo/graph.go848
1 files changed, 848 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/pgo/graph.go b/src/cmd/compile/internal/pgo/graph.go
new file mode 100644
index 0000000..a2cf18f
--- /dev/null
+++ b/src/cmd/compile/internal/pgo/graph.go
@@ -0,0 +1,848 @@
+// Copyright 2014 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package graph collects a set of samples into a directed graph.
+
+// Original file location: https://github.com/google/pprof/tree/main/internal/graph/graph.go
+package pgo
+
+import (
+ "fmt"
+ "internal/profile"
+ "math"
+ "sort"
+ "strings"
+)
+
+// Options encodes the options for constructing a graph
+type Options struct {
+ SampleValue func(s []int64) int64 // Function to compute the value of a sample
+ SampleMeanDivisor func(s []int64) int64 // Function to compute the divisor for mean graphs, or nil
+
+ CallTree bool // Build a tree instead of a graph
+ DropNegative bool // Drop nodes with overall negative values
+
+ KeptNodes NodeSet // If non-nil, only use nodes in this set
+}
+
+// Nodes is an ordered collection of graph nodes.
+type Nodes []*Node
+
+// Node is an entry on a profiling report. It represents a unique
+// program location.
+type Node struct {
+ // Info describes the source location associated to this node.
+ Info NodeInfo
+
+ // Function represents the function that this node belongs to. On
+ // graphs with sub-function resolution (eg line number or
+ // addresses), two nodes in a NodeMap that are part of the same
+ // function have the same value of Node.Function. If the Node
+ // represents the whole function, it points back to itself.
+ Function *Node
+
+ // Values associated to this node. Flat is exclusive to this node,
+ // Cum includes all descendents.
+ Flat, FlatDiv, Cum, CumDiv int64
+
+ // In and out Contains the nodes immediately reaching or reached by
+ // this node.
+ In, Out EdgeMap
+}
+
+// Graph summarizes a performance profile into a format that is
+// suitable for visualization.
+type Graph struct {
+ Nodes Nodes
+}
+
+// FlatValue returns the exclusive value for this node, computing the
+// mean if a divisor is available.
+func (n *Node) FlatValue() int64 {
+ if n.FlatDiv == 0 {
+ return n.Flat
+ }
+ return n.Flat / n.FlatDiv
+}
+
+// CumValue returns the inclusive value for this node, computing the
+// mean if a divisor is available.
+func (n *Node) CumValue() int64 {
+ if n.CumDiv == 0 {
+ return n.Cum
+ }
+ return n.Cum / n.CumDiv
+}
+
+// AddToEdge increases the weight of an edge between two nodes. If
+// there isn't such an edge one is created.
+func (n *Node) AddToEdge(to *Node, v int64, residual, inline bool) {
+ n.AddToEdgeDiv(to, 0, v, residual, inline)
+}
+
+// AddToEdgeDiv increases the weight of an edge between two nodes. If
+// there isn't such an edge one is created.
+func (n *Node) AddToEdgeDiv(to *Node, dv, v int64, residual, inline bool) {
+ if e := n.Out.FindTo(to); e != nil {
+ e.WeightDiv += dv
+ e.Weight += v
+ if residual {
+ e.Residual = true
+ }
+ if !inline {
+ e.Inline = false
+ }
+ return
+ }
+
+ info := &Edge{Src: n, Dest: to, WeightDiv: dv, Weight: v, Residual: residual, Inline: inline}
+ n.Out.Add(info)
+ to.In.Add(info)
+}
+
+// NodeInfo contains the attributes for a node.
+type NodeInfo struct {
+ Name string
+ Address uint64
+ StartLine, Lineno int
+ //File string
+ //OrigName string
+ //Objfile string
+}
+
+// PrintableName calls the Node's Formatter function with a single space separator.
+func (i *NodeInfo) PrintableName() string {
+ return strings.Join(i.NameComponents(), " ")
+}
+
+// NameComponents returns the components of the printable name to be used for a node.
+func (i *NodeInfo) NameComponents() []string {
+ var name []string
+ if i.Address != 0 {
+ name = append(name, fmt.Sprintf("%016x", i.Address))
+ }
+ if fun := i.Name; fun != "" {
+ name = append(name, fun)
+ }
+
+ switch {
+ case i.Lineno != 0:
+ // User requested line numbers, provide what we have.
+ name = append(name, fmt.Sprintf(":%d", i.Lineno))
+ case i.Name != "":
+ // User requested function name. It was already included.
+ default:
+ // Do not leave it empty if there is no information at all.
+ name = append(name, "<unknown>")
+ }
+ return name
+}
+
+// NodeMap maps from a node info struct to a node. It is used to merge
+// report entries with the same info.
+type NodeMap map[NodeInfo]*Node
+
+// NodeSet is a collection of node info structs.
+type NodeSet map[NodeInfo]bool
+
+// NodePtrSet is a collection of nodes. Trimming a graph or tree requires a set
+// of objects which uniquely identify the nodes to keep. In a graph, NodeInfo
+// works as a unique identifier; however, in a tree multiple nodes may share
+// identical NodeInfos. A *Node does uniquely identify a node so we can use that
+// instead. Though a *Node also uniquely identifies a node in a graph,
+// currently, during trimming, graphs are rebuilt from scratch using only the
+// NodeSet, so there would not be the required context of the initial graph to
+// allow for the use of *Node.
+type NodePtrSet map[*Node]bool
+
+// FindOrInsertNode takes the info for a node and either returns a matching node
+// from the node map if one exists, or adds one to the map if one does not.
+// If kept is non-nil, nodes are only added if they can be located on it.
+func (nm NodeMap) FindOrInsertNode(info NodeInfo, kept NodeSet) *Node {
+ if kept != nil {
+ if _, ok := kept[info]; !ok {
+ return nil
+ }
+ }
+
+ if n, ok := nm[info]; ok {
+ return n
+ }
+
+ n := &Node{
+ Info: info,
+ }
+ nm[info] = n
+ if info.Address == 0 && info.Lineno == 0 {
+ // This node represents the whole function, so point Function
+ // back to itself.
+ n.Function = n
+ return n
+ }
+ // Find a node that represents the whole function.
+ info.Address = 0
+ info.Lineno = 0
+ n.Function = nm.FindOrInsertNode(info, nil)
+ return n
+}
+
+// EdgeMap is used to represent the incoming/outgoing edges from a node.
+type EdgeMap []*Edge
+
+func (em EdgeMap) FindTo(n *Node) *Edge {
+ for _, e := range em {
+ if e.Dest == n {
+ return e
+ }
+ }
+ return nil
+}
+
+func (em *EdgeMap) Add(e *Edge) {
+ *em = append(*em, e)
+}
+
+func (em *EdgeMap) Delete(e *Edge) {
+ for i, edge := range *em {
+ if edge == e {
+ (*em)[i] = (*em)[len(*em)-1]
+ *em = (*em)[:len(*em)-1]
+ return
+ }
+ }
+}
+
+// Edge contains any attributes to be represented about edges in a graph.
+type Edge struct {
+ Src, Dest *Node
+ // The summary weight of the edge
+ Weight, WeightDiv int64
+
+ // residual edges connect nodes that were connected through a
+ // separate node, which has been removed from the report.
+ Residual bool
+ // An inline edge represents a call that was inlined into the caller.
+ Inline bool
+}
+
+// WeightValue returns the weight value for this edge, normalizing if a
+// divisor is available.
+func (e *Edge) WeightValue() int64 {
+ if e.WeightDiv == 0 {
+ return e.Weight
+ }
+ return e.Weight / e.WeightDiv
+}
+
+// newGraph computes a graph from a profile.
+func newGraph(prof *profile.Profile, o *Options) *Graph {
+ nodes, locationMap := CreateNodes(prof, o)
+ seenNode := make(map[*Node]bool)
+ seenEdge := make(map[nodePair]bool)
+ for _, sample := range prof.Sample {
+ var w, dw int64
+ w = o.SampleValue(sample.Value)
+ if o.SampleMeanDivisor != nil {
+ dw = o.SampleMeanDivisor(sample.Value)
+ }
+ if dw == 0 && w == 0 {
+ continue
+ }
+ for k := range seenNode {
+ delete(seenNode, k)
+ }
+ for k := range seenEdge {
+ delete(seenEdge, k)
+ }
+ var parent *Node
+ // A residual edge goes over one or more nodes that were not kept.
+ residual := false
+
+ // Group the sample frames, based on a global map.
+ // Count only the last two frames as a call edge. Frames higher up
+ // the stack are unlikely to be repeated calls (e.g. runtime.main
+ // calling main.main). So adding weights to call edges higher up
+ // the stack may be not reflecting the actual call edge weights
+ // in the program. Without a branch profile this is just an
+ // approximation.
+ i := 1
+ if last := len(sample.Location) - 1; last < i {
+ i = last
+ }
+ for ; i >= 0; i-- {
+ l := sample.Location[i]
+ locNodes := locationMap.get(l.ID)
+ for ni := len(locNodes) - 1; ni >= 0; ni-- {
+ n := locNodes[ni]
+ if n == nil {
+ residual = true
+ continue
+ }
+ // Add cum weight to all nodes in stack, avoiding double counting.
+ _, sawNode := seenNode[n]
+ if !sawNode {
+ seenNode[n] = true
+ n.addSample(dw, w, false)
+ }
+ // Update edge weights for all edges in stack, avoiding double counting.
+ if (!sawNode || !seenEdge[nodePair{n, parent}]) && parent != nil && n != parent {
+ seenEdge[nodePair{n, parent}] = true
+ parent.AddToEdgeDiv(n, dw, w, residual, ni != len(locNodes)-1)
+ }
+
+ parent = n
+ residual = false
+ }
+ }
+ if parent != nil && !residual {
+ // Add flat weight to leaf node.
+ parent.addSample(dw, w, true)
+ }
+ }
+
+ return selectNodesForGraph(nodes, o.DropNegative)
+}
+
+func selectNodesForGraph(nodes Nodes, dropNegative bool) *Graph {
+ // Collect nodes into a graph.
+ gNodes := make(Nodes, 0, len(nodes))
+ for _, n := range nodes {
+ if n == nil {
+ continue
+ }
+ if n.Cum == 0 && n.Flat == 0 {
+ continue
+ }
+ if dropNegative && isNegative(n) {
+ continue
+ }
+ gNodes = append(gNodes, n)
+ }
+ return &Graph{gNodes}
+}
+
+type nodePair struct {
+ src, dest *Node
+}
+
+func newTree(prof *profile.Profile, o *Options) (g *Graph) {
+ parentNodeMap := make(map[*Node]NodeMap, len(prof.Sample))
+ for _, sample := range prof.Sample {
+ var w, dw int64
+ w = o.SampleValue(sample.Value)
+ if o.SampleMeanDivisor != nil {
+ dw = o.SampleMeanDivisor(sample.Value)
+ }
+ if dw == 0 && w == 0 {
+ continue
+ }
+ var parent *Node
+ // Group the sample frames, based on a per-node map.
+ for i := len(sample.Location) - 1; i >= 0; i-- {
+ l := sample.Location[i]
+ lines := l.Line
+ if len(lines) == 0 {
+ lines = []profile.Line{{}} // Create empty line to include location info.
+ }
+ for lidx := len(lines) - 1; lidx >= 0; lidx-- {
+ nodeMap := parentNodeMap[parent]
+ if nodeMap == nil {
+ nodeMap = make(NodeMap)
+ parentNodeMap[parent] = nodeMap
+ }
+ n := nodeMap.findOrInsertLine(l, lines[lidx], o)
+ if n == nil {
+ continue
+ }
+ n.addSample(dw, w, false)
+ if parent != nil {
+ parent.AddToEdgeDiv(n, dw, w, false, lidx != len(lines)-1)
+ }
+ parent = n
+ }
+ }
+ if parent != nil {
+ parent.addSample(dw, w, true)
+ }
+ }
+
+ nodes := make(Nodes, len(prof.Location))
+ for _, nm := range parentNodeMap {
+ nodes = append(nodes, nm.nodes()...)
+ }
+ return selectNodesForGraph(nodes, o.DropNegative)
+}
+
+// isNegative returns true if the node is considered as "negative" for the
+// purposes of drop_negative.
+func isNegative(n *Node) bool {
+ switch {
+ case n.Flat < 0:
+ return true
+ case n.Flat == 0 && n.Cum < 0:
+ return true
+ default:
+ return false
+ }
+}
+
+type locationMap struct {
+ s []Nodes // a slice for small sequential IDs
+ m map[uint64]Nodes // fallback for large IDs (unlikely)
+}
+
+func (l *locationMap) add(id uint64, n Nodes) {
+ if id < uint64(len(l.s)) {
+ l.s[id] = n
+ } else {
+ l.m[id] = n
+ }
+}
+
+func (l locationMap) get(id uint64) Nodes {
+ if id < uint64(len(l.s)) {
+ return l.s[id]
+ } else {
+ return l.m[id]
+ }
+}
+
+// CreateNodes creates graph nodes for all locations in a profile. It
+// returns set of all nodes, plus a mapping of each location to the
+// set of corresponding nodes (one per location.Line).
+func CreateNodes(prof *profile.Profile, o *Options) (Nodes, locationMap) {
+ locations := locationMap{make([]Nodes, len(prof.Location)+1), make(map[uint64]Nodes)}
+ nm := make(NodeMap, len(prof.Location))
+ for _, l := range prof.Location {
+ lines := l.Line
+ if len(lines) == 0 {
+ lines = []profile.Line{{}} // Create empty line to include location info.
+ }
+ nodes := make(Nodes, len(lines))
+ for ln := range lines {
+ nodes[ln] = nm.findOrInsertLine(l, lines[ln], o)
+ }
+ locations.add(l.ID, nodes)
+ }
+ return nm.nodes(), locations
+}
+
+func (nm NodeMap) nodes() Nodes {
+ nodes := make(Nodes, 0, len(nm))
+ for _, n := range nm {
+ nodes = append(nodes, n)
+ }
+ return nodes
+}
+
+func (nm NodeMap) findOrInsertLine(l *profile.Location, li profile.Line, o *Options) *Node {
+ var objfile string
+ if m := l.Mapping; m != nil && m.File != "" {
+ objfile = m.File
+ }
+
+ if ni := nodeInfo(l, li, objfile, o); ni != nil {
+ return nm.FindOrInsertNode(*ni, o.KeptNodes)
+ }
+ return nil
+}
+
+func nodeInfo(l *profile.Location, line profile.Line, objfile string, o *Options) *NodeInfo {
+ if line.Function == nil {
+ return &NodeInfo{Address: l.Address}
+ }
+ ni := &NodeInfo{
+ Address: l.Address,
+ Lineno: int(line.Line),
+ Name: line.Function.Name,
+ }
+ ni.StartLine = int(line.Function.StartLine)
+ return ni
+}
+
+// Sum adds the flat and cum values of a set of nodes.
+func (ns Nodes) Sum() (flat int64, cum int64) {
+ for _, n := range ns {
+ flat += n.Flat
+ cum += n.Cum
+ }
+ return
+}
+
+func (n *Node) addSample(dw, w int64, flat bool) {
+ // Update sample value
+ if flat {
+ n.FlatDiv += dw
+ n.Flat += w
+ } else {
+ n.CumDiv += dw
+ n.Cum += w
+ }
+}
+
+// String returns a text representation of a graph, for debugging purposes.
+func (g *Graph) String() string {
+ var s []string
+
+ nodeIndex := make(map[*Node]int, len(g.Nodes))
+
+ for i, n := range g.Nodes {
+ nodeIndex[n] = i + 1
+ }
+
+ for i, n := range g.Nodes {
+ name := n.Info.PrintableName()
+ var in, out []int
+
+ for _, from := range n.In {
+ in = append(in, nodeIndex[from.Src])
+ }
+ for _, to := range n.Out {
+ out = append(out, nodeIndex[to.Dest])
+ }
+ s = append(s, fmt.Sprintf("%d: %s[flat=%d cum=%d] %x -> %v ", i+1, name, n.Flat, n.Cum, in, out))
+ }
+ return strings.Join(s, "\n")
+}
+
+// DiscardLowFrequencyNodes returns a set of the nodes at or over a
+// specific cum value cutoff.
+func (g *Graph) DiscardLowFrequencyNodes(nodeCutoff int64) NodeSet {
+ return makeNodeSet(g.Nodes, nodeCutoff)
+}
+
+// DiscardLowFrequencyNodePtrs returns a NodePtrSet of nodes at or over a
+// specific cum value cutoff.
+func (g *Graph) DiscardLowFrequencyNodePtrs(nodeCutoff int64) NodePtrSet {
+ cutNodes := getNodesAboveCumCutoff(g.Nodes, nodeCutoff)
+ kept := make(NodePtrSet, len(cutNodes))
+ for _, n := range cutNodes {
+ kept[n] = true
+ }
+ return kept
+}
+
+func makeNodeSet(nodes Nodes, nodeCutoff int64) NodeSet {
+ cutNodes := getNodesAboveCumCutoff(nodes, nodeCutoff)
+ kept := make(NodeSet, len(cutNodes))
+ for _, n := range cutNodes {
+ kept[n.Info] = true
+ }
+ return kept
+}
+
+// getNodesAboveCumCutoff returns all the nodes which have a Cum value greater
+// than or equal to cutoff.
+func getNodesAboveCumCutoff(nodes Nodes, nodeCutoff int64) Nodes {
+ cutoffNodes := make(Nodes, 0, len(nodes))
+ for _, n := range nodes {
+ if abs64(n.Cum) < nodeCutoff {
+ continue
+ }
+ cutoffNodes = append(cutoffNodes, n)
+ }
+ return cutoffNodes
+}
+
+// TrimLowFrequencyEdges removes edges that have less than
+// the specified weight. Returns the number of edges removed
+func (g *Graph) TrimLowFrequencyEdges(edgeCutoff int64) int {
+ var droppedEdges int
+ for _, n := range g.Nodes {
+ for _, e := range n.In {
+ if abs64(e.Weight) < edgeCutoff {
+ n.In.Delete(e)
+ e.Src.Out.Delete(e)
+ droppedEdges++
+ }
+ }
+ }
+ return droppedEdges
+}
+
+// SortNodes sorts the nodes in a graph based on a specific heuristic.
+func (g *Graph) SortNodes(cum bool, visualMode bool) {
+ // Sort nodes based on requested mode
+ switch {
+ case visualMode:
+ // Specialized sort to produce a more visually-interesting graph
+ g.Nodes.Sort(EntropyOrder)
+ case cum:
+ g.Nodes.Sort(CumNameOrder)
+ default:
+ g.Nodes.Sort(FlatNameOrder)
+ }
+}
+
+// SelectTopNodePtrs returns a set of the top maxNodes *Node in a graph.
+func (g *Graph) SelectTopNodePtrs(maxNodes int, visualMode bool) NodePtrSet {
+ set := make(NodePtrSet)
+ for _, node := range g.selectTopNodes(maxNodes, visualMode) {
+ set[node] = true
+ }
+ return set
+}
+
+// SelectTopNodes returns a set of the top maxNodes nodes in a graph.
+func (g *Graph) SelectTopNodes(maxNodes int, visualMode bool) NodeSet {
+ return makeNodeSet(g.selectTopNodes(maxNodes, visualMode), 0)
+}
+
+// selectTopNodes returns a slice of the top maxNodes nodes in a graph.
+func (g *Graph) selectTopNodes(maxNodes int, visualMode bool) Nodes {
+ if maxNodes > len(g.Nodes) {
+ maxNodes = len(g.Nodes)
+ }
+ return g.Nodes[:maxNodes]
+}
+
+// nodeSorter is a mechanism used to allow a report to be sorted
+// in different ways.
+type nodeSorter struct {
+ rs Nodes
+ less func(l, r *Node) bool
+}
+
+func (s nodeSorter) Len() int { return len(s.rs) }
+func (s nodeSorter) Swap(i, j int) { s.rs[i], s.rs[j] = s.rs[j], s.rs[i] }
+func (s nodeSorter) Less(i, j int) bool { return s.less(s.rs[i], s.rs[j]) }
+
+// Sort reorders a slice of nodes based on the specified ordering
+// criteria. The result is sorted in decreasing order for (absolute)
+// numeric quantities, alphabetically for text, and increasing for
+// addresses.
+func (ns Nodes) Sort(o NodeOrder) error {
+ var s nodeSorter
+
+ switch o {
+ case FlatNameOrder:
+ s = nodeSorter{ns,
+ func(l, r *Node) bool {
+ if iv, jv := abs64(l.Flat), abs64(r.Flat); iv != jv {
+ return iv > jv
+ }
+ if iv, jv := l.Info.PrintableName(), r.Info.PrintableName(); iv != jv {
+ return iv < jv
+ }
+ if iv, jv := abs64(l.Cum), abs64(r.Cum); iv != jv {
+ return iv > jv
+ }
+ return compareNodes(l, r)
+ },
+ }
+ case FlatCumNameOrder:
+ s = nodeSorter{ns,
+ func(l, r *Node) bool {
+ if iv, jv := abs64(l.Flat), abs64(r.Flat); iv != jv {
+ return iv > jv
+ }
+ if iv, jv := abs64(l.Cum), abs64(r.Cum); iv != jv {
+ return iv > jv
+ }
+ if iv, jv := l.Info.PrintableName(), r.Info.PrintableName(); iv != jv {
+ return iv < jv
+ }
+ return compareNodes(l, r)
+ },
+ }
+ case NameOrder:
+ s = nodeSorter{ns,
+ func(l, r *Node) bool {
+ if iv, jv := l.Info.Name, r.Info.Name; iv != jv {
+ return iv < jv
+ }
+ return compareNodes(l, r)
+ },
+ }
+ case FileOrder:
+ s = nodeSorter{ns,
+ func(l, r *Node) bool {
+ if iv, jv := l.Info.StartLine, r.Info.StartLine; iv != jv {
+ return iv < jv
+ }
+ return compareNodes(l, r)
+ },
+ }
+ case AddressOrder:
+ s = nodeSorter{ns,
+ func(l, r *Node) bool {
+ if iv, jv := l.Info.Address, r.Info.Address; iv != jv {
+ return iv < jv
+ }
+ return compareNodes(l, r)
+ },
+ }
+ case CumNameOrder, EntropyOrder:
+ // Hold scoring for score-based ordering
+ var score map[*Node]int64
+ scoreOrder := func(l, r *Node) bool {
+ if iv, jv := abs64(score[l]), abs64(score[r]); iv != jv {
+ return iv > jv
+ }
+ if iv, jv := l.Info.PrintableName(), r.Info.PrintableName(); iv != jv {
+ return iv < jv
+ }
+ if iv, jv := abs64(l.Flat), abs64(r.Flat); iv != jv {
+ return iv > jv
+ }
+ return compareNodes(l, r)
+ }
+
+ switch o {
+ case CumNameOrder:
+ score = make(map[*Node]int64, len(ns))
+ for _, n := range ns {
+ score[n] = n.Cum
+ }
+ s = nodeSorter{ns, scoreOrder}
+ case EntropyOrder:
+ score = make(map[*Node]int64, len(ns))
+ for _, n := range ns {
+ score[n] = entropyScore(n)
+ }
+ s = nodeSorter{ns, scoreOrder}
+ }
+ default:
+ return fmt.Errorf("report: unrecognized sort ordering: %d", o)
+ }
+ sort.Sort(s)
+ return nil
+}
+
+// compareNodes compares two nodes to provide a deterministic ordering
+// between them. Two nodes cannot have the same Node.Info value.
+func compareNodes(l, r *Node) bool {
+ return fmt.Sprint(l.Info) < fmt.Sprint(r.Info)
+}
+
+// entropyScore computes a score for a node representing how important
+// it is to include this node on a graph visualization. It is used to
+// sort the nodes and select which ones to display if we have more
+// nodes than desired in the graph. This number is computed by looking
+// at the flat and cum weights of the node and the incoming/outgoing
+// edges. The fundamental idea is to penalize nodes that have a simple
+// fallthrough from their incoming to the outgoing edge.
+func entropyScore(n *Node) int64 {
+ score := float64(0)
+
+ if len(n.In) == 0 {
+ score++ // Favor entry nodes
+ } else {
+ score += edgeEntropyScore(n, n.In, 0)
+ }
+
+ if len(n.Out) == 0 {
+ score++ // Favor leaf nodes
+ } else {
+ score += edgeEntropyScore(n, n.Out, n.Flat)
+ }
+
+ return int64(score*float64(n.Cum)) + n.Flat
+}
+
+// edgeEntropyScore computes the entropy value for a set of edges
+// coming in or out of a node. Entropy (as defined in information
+// theory) refers to the amount of information encoded by the set of
+// edges. A set of edges that have a more interesting distribution of
+// samples gets a higher score.
+func edgeEntropyScore(n *Node, edges EdgeMap, self int64) float64 {
+ score := float64(0)
+ total := self
+ for _, e := range edges {
+ if e.Weight > 0 {
+ total += abs64(e.Weight)
+ }
+ }
+ if total != 0 {
+ for _, e := range edges {
+ frac := float64(abs64(e.Weight)) / float64(total)
+ score += -frac * math.Log2(frac)
+ }
+ if self > 0 {
+ frac := float64(abs64(self)) / float64(total)
+ score += -frac * math.Log2(frac)
+ }
+ }
+ return score
+}
+
+// NodeOrder sets the ordering for a Sort operation
+type NodeOrder int
+
+// Sorting options for node sort.
+const (
+ FlatNameOrder NodeOrder = iota
+ FlatCumNameOrder
+ CumNameOrder
+ NameOrder
+ FileOrder
+ AddressOrder
+ EntropyOrder
+)
+
+// Sort returns a slice of the edges in the map, in a consistent
+// order. The sort order is first based on the edge weight
+// (higher-to-lower) and then by the node names to avoid flakiness.
+func (e EdgeMap) Sort() []*Edge {
+ el := make(edgeList, 0, len(e))
+ for _, w := range e {
+ el = append(el, w)
+ }
+
+ sort.Sort(el)
+ return el
+}
+
+// Sum returns the total weight for a set of nodes.
+func (e EdgeMap) Sum() int64 {
+ var ret int64
+ for _, edge := range e {
+ ret += edge.Weight
+ }
+ return ret
+}
+
+type edgeList []*Edge
+
+func (el edgeList) Len() int {
+ return len(el)
+}
+
+func (el edgeList) Less(i, j int) bool {
+ if el[i].Weight != el[j].Weight {
+ return abs64(el[i].Weight) > abs64(el[j].Weight)
+ }
+
+ from1 := el[i].Src.Info.PrintableName()
+ from2 := el[j].Src.Info.PrintableName()
+ if from1 != from2 {
+ return from1 < from2
+ }
+
+ to1 := el[i].Dest.Info.PrintableName()
+ to2 := el[j].Dest.Info.PrintableName()
+
+ return to1 < to2
+}
+
+func (el edgeList) Swap(i, j int) {
+ el[i], el[j] = el[j], el[i]
+}
+
+func abs64(i int64) int64 {
+ if i < 0 {
+ return -i
+ }
+ return i
+}
generated by cgit v1.2.3 (git 2.39.1) at 2025-01-01 18:06:41 +0000