| // Copyright ©2019 The Gonum Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| package kdtree |
| |
| var ( |
| _ Interface = nbPoints{} |
| _ Comparable = nbPoint{} |
| ) |
| |
| // nbRandoms is the maximum number of random values to sample for calculation of median of |
| // random elements. |
| var nbRandoms = 100 |
| |
| // nbPoint represents a point in a k-d space that satisfies the Comparable interface. |
| type nbPoint Point |
| |
| func (p nbPoint) Compare(c Comparable, d Dim) float64 { q := c.(nbPoint); return p[d] - q[d] } |
| func (p nbPoint) Dims() int { return len(p) } |
| func (p nbPoint) Distance(c Comparable) float64 { |
| q := c.(nbPoint) |
| var sum float64 |
| for dim, c := range p { |
| d := c - q[dim] |
| sum += d * d |
| } |
| return sum |
| } |
| |
| // nbPoints is a collection of point values that satisfies the Interface. |
| type nbPoints []nbPoint |
| |
| func (p nbPoints) Index(i int) Comparable { return p[i] } |
| func (p nbPoints) Len() int { return len(p) } |
| func (p nbPoints) Pivot(d Dim) int { return nbPlane{nbPoints: p, Dim: d}.Pivot() } |
| func (p nbPoints) Slice(start, end int) Interface { return p[start:end] } |
| |
| // nbPlane is a wrapping type that allows a Points type be pivoted on a dimension. |
| type nbPlane struct { |
| Dim |
| nbPoints |
| } |
| |
| func (p nbPlane) Less(i, j int) bool { return p.nbPoints[i][p.Dim] < p.nbPoints[j][p.Dim] } |
| func (p nbPlane) Pivot() int { return Partition(p, MedianOfRandoms(p, nbRandoms)) } |
| func (p nbPlane) Slice(start, end int) SortSlicer { p.nbPoints = p.nbPoints[start:end]; return p } |
| func (p nbPlane) Swap(i, j int) { |
| p.nbPoints[i], p.nbPoints[j] = p.nbPoints[j], p.nbPoints[i] |
| } |