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ergo/vendor/github.com/tidwall/rtree/base/load.go

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package base
import "math"
// Load bulk load items into the R-tree.
func (tr *RTree) Load(mins, maxs [][]float64, items []interface{}) {
if len(items) < tr.minEntries {
for i := 0; i < len(items); i++ {
tr.Insert(mins[i], maxs[i], items[i])
}
return
}
// prefill the items
fitems := make([]*treeNode, len(items))
for i := 0; i < len(items); i++ {
item := &treeItem{min: mins[i], max: maxs[i], item: items[i]}
fitems[i] = item.unsafeNode()
}
// following equations are defined in the paper describing OMT
N := len(fitems)
M := tr.maxEntries
h := int(math.Ceil(math.Log(float64(N)) / math.Log(float64(M))))
Nsubtree := int(math.Pow(float64(M), float64(h-1)))
S := int(math.Ceil(math.Sqrt(float64(N) / float64(Nsubtree))))
// sort by the initial axis
axis := 0
sortByAxis(fitems, axis)
// build the root node. it's split differently from the subtrees.
children := make([]*treeNode, 0, S)
for i := 0; i < S; i++ {
var part []*treeNode
if i == S-1 {
// last split
part = fitems[len(fitems)/S*i:]
} else {
part = fitems[len(fitems)/S*i : len(fitems)/S*(i+1)]
}
children = append(children, tr.omt(part, h-1, axis+1))
}
node := tr.createNode(children)
node.leaf = false
node.height = h
tr.calcBBox(node)
if tr.data.count == 0 {
// save as is if tree is empty
tr.data = node
} else if tr.data.height == node.height {
// split root if trees have the same height
tr.splitRoot(tr.data, node)
} else {
if tr.data.height < node.height {
// swap trees if inserted one is bigger
tr.data, node = node, tr.data
}
// insert the small tree into the large tree at appropriate level
tr.insert(node, nil, tr.data.height-node.height-1, true)
}
}
func (tr *RTree) omt(fitems []*treeNode, h, axis int) *treeNode {
if len(fitems) <= tr.maxEntries {
// reached leaf level; return leaf
children := make([]*treeNode, len(fitems))
copy(children, fitems)
node := tr.createNode(children)
node.height = h
tr.calcBBox(node)
return node
}
// sort the items on a different axis than the previous level.
sortByAxis(fitems, axis%tr.dims)
children := make([]*treeNode, 0, tr.maxEntries)
partsz := len(fitems) / tr.maxEntries
for i := 0; i < tr.maxEntries; i++ {
var part []*treeNode
if i == tr.maxEntries-1 {
// last part
part = fitems[partsz*i:]
} else {
part = fitems[partsz*i : partsz*(i+1)]
}
children = append(children, tr.omt(part, h-1, axis+1))
}
node := tr.createNode(children)
node.height = h
node.leaf = false
tr.calcBBox(node)
return node
}