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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,26 +1,65 @@ | ||
| package gago | ||
|
|
||
| // A Metric returns the distance between two genomes. | ||
| type Metric func(a, b Individual) float64 | ||
|
|
||
| // A DistanceMemoizer computes and stores Metric calculations. | ||
| type DistanceMemoizer struct { | ||
| Metric func(a, b Genome) float64 | ||
| Distances map[Genome]map[Genome]float64 | ||
| Metric Metric | ||
| Distances map[string]map[string]float64 | ||
| nCalculations int // Total number of calls to Metric for testing purposes | ||
| } | ||
|
|
||
| func makeDistanceMemoizer(metric func(a, b Genome) float64) DistanceMemoizer { | ||
| // makeDistanceMemoizer initializes a DistanceMemoizer. | ||
| func makeDistanceMemoizer(metric Metric) DistanceMemoizer { | ||
| return DistanceMemoizer{ | ||
| Metric: metric, | ||
| Distances: make(map[Genome]map[Genome]float64), | ||
| Distances: make(map[string]map[string]float64), | ||
| } | ||
| } | ||
|
|
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| func (dm *DistanceMemoizer) getDistance(a, b Genome) float64 { | ||
| if dist, ok := dm.Distances[a][b]; ok { | ||
| return dist | ||
| // GetDistance returns the distance between two Individuals based on the | ||
| // DistanceMemoizer's Metric field. If the two individuals share the same ID | ||
| // then GetDistance returns 0. DistanceMemoizer stores the calculated distances | ||
| // so that if GetDistance is called twice with the two same Individuals then | ||
| // the second call will return the stored distance instead of recomputing it. | ||
| func (dm *DistanceMemoizer) GetDistance(a, b Individual) float64 { | ||
| // Check if the two individuals are the same before proceding | ||
| if a.ID == b.ID { | ||
| return 0 | ||
| } | ||
| // Create maps if the genomes have never been encountered | ||
| if _, ok := dm.Distances[a.ID]; !ok { | ||
| dm.Distances[a.ID] = make(map[string]float64) | ||
| } else { | ||
| // Check if the distance between the two genomes has been calculated | ||
| if dist, ok := dm.Distances[a.ID][b.ID]; ok { | ||
| return dist | ||
| } | ||
| } | ||
| if dist, ok := dm.Distances[b][a]; ok { | ||
| return dist | ||
| if _, ok := dm.Distances[b.ID]; !ok { | ||
| dm.Distances[b.ID] = make(map[string]float64) | ||
| } else { | ||
| if dist, ok := dm.Distances[b.ID][a.ID]; ok { | ||
| return dist | ||
| } | ||
| } | ||
| // Calculate the distance between the genomes and memoize it | ||
| var dist = dm.Metric(a, b) | ||
| dm.Distances[a][b] = dist | ||
| dm.Distances[b][a] = dist | ||
| dm.Distances[a.ID][b.ID] = dist | ||
| dm.Distances[b.ID][a.ID] = dist | ||
| dm.nCalculations++ | ||
| return dist | ||
| } | ||
|
|
||
| // Return the average distance between a Individual and a slice of Individuals. | ||
| func calcAvgDistances(indis Individuals, dm DistanceMemoizer) map[string]float64 { | ||
| var avgDistances = make(map[string]float64) | ||
| for _, a := range indis { | ||
| for _, b := range indis { | ||
| avgDistances[a.ID] += dm.GetDistance(a, b) | ||
| } | ||
| avgDistances[a.ID] /= float64(len(indis) - 1) | ||
| } | ||
| return avgDistances | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,19 +1,50 @@ | ||
| package gago | ||
|
|
||
| import ( | ||
| "math" | ||
| "testing" | ||
| ) | ||
|
|
||
| func L1Distance(x1, x2 Genome) (dist float64) { | ||
| var g1 = x1.(Vector) | ||
| var g2 = x2.(Vector) | ||
| for i := range g1 { | ||
| dist += math.Abs(g1[i] - g2[i]) | ||
| } | ||
| return | ||
| } | ||
|
|
||
| func TestDistanceMemoizer(t *testing.T) { | ||
| var dm = makeDistanceMemoizer(L1Distance) | ||
| var ( | ||
| dm = makeDistanceMemoizer(l1Distance) | ||
| a = Individual{Genome: Vector{1, 1, 1}, ID: "1"} | ||
| b = Individual{Genome: Vector{3, 3, 3}, ID: "2"} | ||
| c = Individual{Genome: Vector{6, 6, 6}, ID: "3"} | ||
| ) | ||
| // Check the number of calculations is initially 0 | ||
| if dm.nCalculations != 0 { | ||
| t.Error("nCalculations is not initialized to 0") | ||
| } | ||
| // Check the distance between the 1st and itself | ||
| if dm.GetDistance(a, a) != 0 { | ||
| t.Error("Wrong calculated distance") | ||
| } | ||
| // Check the number of calculations is initially 0 | ||
| if dm.nCalculations != 0 { | ||
| t.Error("nCalculations should not have increased") | ||
| } | ||
| // Check the distance between the 1st and the 2nd individual | ||
| if dm.GetDistance(a, b) != 6 { | ||
| t.Error("Wrong calculated distance") | ||
| } | ||
| // Check the number of calculations has increased by 1 | ||
| if dm.nCalculations != 1 { | ||
| t.Error("nCalculations has not increased") | ||
| } | ||
| // Check the distance between the 2nd and the 1st individual | ||
| if dm.GetDistance(b, a) != 6 { | ||
| t.Error("Wrong calculated distance") | ||
| } | ||
| // Check the number of calculations has not increased | ||
| if dm.nCalculations != 1 { | ||
| t.Error("nCalculations has increased") | ||
| } | ||
| // Check the distance between the 1st and the 3rd individual | ||
| if dm.GetDistance(a, c) != 15 { | ||
| t.Error("Wrong calculated distance") | ||
| } | ||
| // Check the distance between the 1st and the 3rd individual | ||
| if dm.GetDistance(b, c) != 9 { | ||
| t.Error("Wrong calculated distance") | ||
| } | ||
| } |
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