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ergo/vendor/github.com/tidwall/rtred/base/knn.go
Shivaram Lingamneni fd3cbab6ee bump buntdb to v1.2.3
Potentially fixes the database corruption seen on #1603
2021-04-01 20:45:15 -04:00

99 lines
2.0 KiB
Go

package base
import (
"github.com/tidwall/tinyqueue"
)
type queueItem struct {
node *treeNode
isItem bool
dist float64
}
func (item *queueItem) Less(b tinyqueue.Item) bool {
return item.dist < b.(*queueItem).dist
}
// KNN returns items nearest to farthest. The dist param is the "box distance".
func (tr *RTree) KNN(min, max []float64, center bool, iter func(item interface{}, dist float64) bool) bool {
var isBox bool
knnPoint := make([]float64, tr.dims)
bbox := &treeNode{min: min, max: max}
for i := 0; i < tr.dims; i++ {
knnPoint[i] = (bbox.min[i] + bbox.max[i]) / 2
if !isBox && bbox.min[i] != bbox.max[i] {
isBox = true
}
}
node := tr.data
queue := tinyqueue.New(nil)
for node != nil {
for i := 0; i < node.count; i++ {
child := node.children[i]
var dist float64
if isBox {
dist = boxDistRect(bbox, child)
} else {
dist = boxDistPoint(knnPoint, child)
}
queue.Push(&queueItem{node: child, isItem: node.leaf, dist: dist})
}
for queue.Len() > 0 && queue.Peek().(*queueItem).isItem {
item := queue.Pop().(*queueItem)
if !iter(item.node.unsafeItem().item, item.dist) {
return false
}
}
last := queue.Pop()
if last != nil {
node = (*treeNode)(last.(*queueItem).node)
} else {
node = nil
}
}
return true
}
func boxDistRect(a, b *treeNode) float64 {
var dist float64
for i := 0; i < len(a.min); i++ {
var min, max float64
if a.min[i] > b.min[i] {
min = a.min[i]
} else {
min = b.min[i]
}
if a.max[i] < b.max[i] {
max = a.max[i]
} else {
max = b.max[i]
}
squared := min - max
if squared > 0 {
dist += squared * squared
}
}
return dist
}
func boxDistPoint(point []float64, childBox *treeNode) float64 {
var dist float64
for i := 0; i < len(point); i++ {
d := axisDist(point[i], childBox.min[i], childBox.max[i])
dist += d * d
}
return dist
}
func axisDist(k, min, max float64) float64 {
if k < min {
return min - k
}
if k <= max {
return 0
}
return k - max
}