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left_right_assigner.go
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/
left_right_assigner.go
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package plugin
import (
"log"
"math/rand"
"sort"
"github.com/hiro4bbh/sticker"
)
// LeftRightAssigner_greedyBottomRanks assigns left or right label as moving each entry which has that bottom-ranked labels from left to right.
// This is registered to sticker.LeftRightAssigners.
//
// This function returns no error currently.
func LeftRightAssigner_greedyBottomRanks(ds *sticker.Dataset, delta []bool, debug *log.Logger) error {
for i := range delta {
delta[i] = false
}
labelFreq := make(map[uint32]float32)
for _, yi := range ds.Y {
for _, label := range yi {
labelFreq[label]++
}
}
labelRankTopL := sticker.RankTopK(labelFreq, uint(len(labelFreq)))
n, nlefts, nrights := ds.Size(), ds.Size(), 0
for k := len(labelRankTopL) - 1; nlefts > n/2; k-- {
if debug != nil {
debug.Printf("LeftRightAssigner(greedyBottomRanks): optimizing the allocation on %d in left and %d in right ...", nlefts, nrights)
}
label := labelRankTopL[k]
for i, yi := range ds.Y {
if delta[i] {
continue
}
for _, l := range yi {
if l == label {
delta[i] = true
nlefts--
nrights++
break
}
}
}
}
return nil
}
// LeftRightAssigner_nDCG assigns left or right on each label as maximizing the sum of left and right utilities with nDCGs.
// This is registered to LeftRightAssigners.
//
// This function return no error currently.
//
// NOTICE: In calculating nDCG, this function uses the base of logarithm is 2 because of precision.
func LeftRightAssigner_nDCG(ds *sticker.Dataset, delta []bool, debug *log.Logger) error {
delta0, delta1 := make([]bool, len(delta)), make([]bool, len(delta))
copy(delta0, delta)
objval0 := float32(0.0)
for {
if debug != nil {
nLeftRights := make(map[bool]int)
for _, deltai := range delta0 {
nLeftRights[deltai]++
}
debug.Printf("LeftRightAssigner_nDCG: optimizing the allocation on %d in left and %d in right (objval0=%g) ...", nLeftRights[false], nLeftRights[true], objval0)
}
// Construct the left/right label distributions r^-/r^+.
leftLabelFreq, rightLabelFreq := make(map[uint32]float32), make(map[uint32]float32)
for i, yi := range ds.Y {
labelFreq := leftLabelFreq
if delta0[i] {
labelFreq = rightLabelFreq
}
Z := 1.0 / sticker.IdealDCG(uint(len(yi)))
for _, label := range yi {
labelFreq[label] += Z
}
}
leftLabelRanks, rightLabelRanks := sticker.RankTopK(leftLabelFreq, uint(len(leftLabelFreq))), sticker.RankTopK(rightLabelFreq, uint(len(rightLabelFreq)))
leftLabelInvRanks, rightLabelInvRanks := sticker.InvertRanks(leftLabelRanks), sticker.InvertRanks(rightLabelRanks)
objval := float32(0.0)
for i, yi := range ds.Y {
// v_i^- = L_{nDCG@K}(y_i, r^-), v_i^+ = L_{nDCG@K}(y_i, r^+)
vn, vp := float32(0.0), float32(0.0)
for _, label := range yi {
if rank, ok := leftLabelInvRanks[label]; ok {
vn += 1.0 / sticker.LogBinary32(1.0+float32(rank))
}
if rank, ok := rightLabelInvRanks[label]; ok {
vp += 1.0 / sticker.LogBinary32(1.0+float32(rank))
}
}
if vn < vp {
delta1[i] = true
objval += vp
} else {
delta1[i] = false
objval += vn
}
}
if objval0 >= objval {
break
}
delta0, delta1 = delta1, delta0
objval0 = objval
}
copy(delta, delta0)
return nil
}
// LeftRightAssigner_none assigns left or right on each label with the given initialized delta, so the label assignment won't change from the given initialized delta.
// This is registered to LeftRightAssigners.
//
// This function returns no error.
func LeftRightAssigner_none(ds *sticker.Dataset, delta []bool, debug *log.Logger) error {
return nil
}
// LeftRightAssigner is the type of the left/right assigners.
// An assigner modifies delta to store the result of the assignment.
// delta is also used as the initial value.
type LeftRightAssigner func(ds *sticker.Dataset, delta []bool, debug *log.Logger) error
// LeftRightAssigners is the map from the assigner name to the left/right assigner.
var LeftRightAssigners = map[string]LeftRightAssigner{
"greedyBottomRanks": LeftRightAssigner_greedyBottomRanks,
"nDCG": LeftRightAssigner_nDCG,
"none": LeftRightAssigner_none,
}
// DefaultLeftRightAssignerName is the default LeftRightAssigner name.
const DefaultLeftRightAssignerName = "nDCG"
func _LeftRightAssignInitializer_topLabels(isGraph bool, ds *sticker.Dataset, params *LabelTreeParameters, rng *rand.Rand, debug *log.Logger) []bool {
labelFreq := make(map[uint32]float32)
for _, yi := range ds.Y {
for _, label := range yi {
labelFreq[label]++
}
}
K := 16 * params.K
if K > uint(len(labelFreq)) {
K = uint(len(labelFreq))
}
labelRankTopK := sticker.RankTopK(labelFreq, K)
labelInvRankTopK := sticker.InvertRanks(labelRankTopK)
labelFreqTopK := make(map[uint32]float32)
for _, label := range labelRankTopK {
labelFreqTopK[label] = labelFreq[label]
}
A := make([]float32, K*K)
if isGraph {
for _, yi := range ds.Y {
for _, label1 := range yi {
rank1p, ok := labelInvRankTopK[label1]
if !ok {
continue
}
for _, label2 := range yi {
if rank2p, ok := labelInvRankTopK[label2]; ok && rank1p != rank2p {
A[uint(rank1p-1)*K+uint(rank2p-1)]++
}
}
}
}
} else {
for _, yi := range ds.Y {
labelRanks := make(sticker.KeyValues32OrderedByValue, 0, len(yi))
for _, label := range yi {
if rank, ok := labelInvRankTopK[label]; ok {
labelRanks = append(labelRanks, sticker.KeyValue32{label, float32(rank)})
}
}
sort.Sort(labelRanks)
for j := 0; j < len(labelRanks)-1; j++ {
A[uint(labelRanks[j].Value-1)*K+uint(labelRanks[j+1].Value-1)]++
A[uint(labelRanks[j+1].Value-1)*K+uint(labelRanks[j].Value-1)]++
}
}
}
deltaLabel, _ := BipartitionWeightedGraph(uint64(K), uint64(params.MaxEntriesInLeaf), A)
delta := make([]bool, ds.Size())
for i, yi := range ds.Y {
dn, dp := 0, 0
for _, label := range yi {
if rank, ok := labelInvRankTopK[label]; ok {
if deltaLabel[rank-1] {
dp++
} else {
dn++
}
}
}
if dp >= dn {
if dn+dp == 0 {
delta[i] = rng.Float32() >= 0.5
} else {
delta[i] = true
}
} else if dp < dn {
delta[i] = false
}
}
return delta
}
// LeftRightAssignInitializer_topLabelGraph returns the delta slice initialized with the cutting of the top-label graph.
// This is registered to sticker.LeftRightAssignInitializers.
func LeftRightAssignInitializer_topLabelGraph(ds *sticker.Dataset, params *LabelTreeParameters, rng *rand.Rand, debug *log.Logger) []bool {
return _LeftRightAssignInitializer_topLabels(true, ds, params, rng, debug)
}
// LeftRightAssignInitializer_topLabelGraph returns the delta slice initialized with the cutting of the top-labels tree.
// This is registered to sticker.LeftRightAssignInitializers.
func LeftRightAssignInitializer_topLabelTree(ds *sticker.Dataset, params *LabelTreeParameters, rng *rand.Rand, debug *log.Logger) []bool {
return _LeftRightAssignInitializer_topLabels(false, ds, params, rng, debug)
}
// LeftRightAssignInitializer_uniform returns the delta slice initialized with the samples from uniform probability distribution.
// This is registered to LeftRightAssignInitializers.
func LeftRightAssignInitializer_uniform(ds *sticker.Dataset, params *LabelTreeParameters, rng *rand.Rand, debug *log.Logger) []bool {
delta := make([]bool, ds.Size())
for i := range delta {
delta[i] = rng.Float32() >= 0.5
}
return delta
}
// LeftRightAssignInitializer is the type of the left/right assignment initializers.
// An initializer returns the initialized left/right assignment slice.
type LeftRightAssignInitializer func(ds *sticker.Dataset, params *LabelTreeParameters, rng *rand.Rand, debug *log.Logger) []bool
// LeftRightAssignInitializers is the map from the initializer name to the corresponding left/right assignment initializer.
var LeftRightAssignInitializers = map[string]LeftRightAssignInitializer{
"topLabelGraph": LeftRightAssignInitializer_topLabelGraph,
"topLabelTree": LeftRightAssignInitializer_topLabelTree,
"uniform": LeftRightAssignInitializer_uniform,
}
// DefaultLeftRightAssignInitializerName is the default LeftRightAssignInitializer name.
const DefaultLeftRightAssignInitializerName = "uniform"