github.com/jingcheng-WU/gonum@v0.9.1-0.20210323123734-f1a2a11a8f7b/spatial/kdtree/nbpoints_test.go (about)

     1  // Copyright ©2019 The Gonum Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package kdtree
     6  
     7  var (
     8  	_ Interface  = nbPoints{}
     9  	_ Comparable = nbPoint{}
    10  )
    11  
    12  // nbRandoms is the maximum number of random values to sample for calculation of median of
    13  // random elements.
    14  var nbRandoms = 100
    15  
    16  // nbPoint represents a point in a k-d space that satisfies the Comparable interface.
    17  type nbPoint Point
    18  
    19  func (p nbPoint) Compare(c Comparable, d Dim) float64 { q := c.(nbPoint); return p[d] - q[d] }
    20  func (p nbPoint) Dims() int                           { return len(p) }
    21  func (p nbPoint) Distance(c Comparable) float64 {
    22  	q := c.(nbPoint)
    23  	var sum float64
    24  	for dim, c := range p {
    25  		d := c - q[dim]
    26  		sum += d * d
    27  	}
    28  	return sum
    29  }
    30  
    31  // nbPoints is a collection of point values that satisfies the Interface.
    32  type nbPoints []nbPoint
    33  
    34  func (p nbPoints) Index(i int) Comparable         { return p[i] }
    35  func (p nbPoints) Len() int                       { return len(p) }
    36  func (p nbPoints) Pivot(d Dim) int                { return nbPlane{nbPoints: p, Dim: d}.Pivot() }
    37  func (p nbPoints) Slice(start, end int) Interface { return p[start:end] }
    38  
    39  // nbPlane is a wrapping type that allows a Points type be pivoted on a dimension.
    40  type nbPlane struct {
    41  	Dim
    42  	nbPoints
    43  }
    44  
    45  func (p nbPlane) Less(i, j int) bool              { return p.nbPoints[i][p.Dim] < p.nbPoints[j][p.Dim] }
    46  func (p nbPlane) Pivot() int                      { return Partition(p, MedianOfRandoms(p, nbRandoms)) }
    47  func (p nbPlane) Slice(start, end int) SortSlicer { p.nbPoints = p.nbPoints[start:end]; return p }
    48  func (p nbPlane) Swap(i, j int) {
    49  	p.nbPoints[i], p.nbPoints[j] = p.nbPoints[j], p.nbPoints[i]
    50  }