Merge pull request #39 from nextmv-io/ds/chore/fast-generator

Improve multi stop plan unit generation

Author: dirkschumacher

solution_move_stops_generator.go

@@ -2,6 +2,10 @@
 
 package nextroute
 
+import (
+	"slices"
+)
+
 // SolutionMoveStopsGeneratorChannel generates all possible moves for a given
 // vehicle and plan unit.
 //
@@ -108,11 +112,13 @@ func SolutionMoveStopsGenerator(
 		return
 	}
 
-	// TODO: we can reuse the stopPositions slice from m
-	positions := make([]StopPosition, len(source))
+	positions := m.(*solutionMoveStopsImpl).stopPositions[:0]
+	positions = slices.Grow(positions, len(source))
 	for idx := range source {
-		positions[idx].stopIndex = source[idx].index
-		positions[idx].solution = source[idx].solution
+		positions = append(positions, StopPosition{
+			stopIndex: source[idx].index,
+			solution:  source[idx].solution,
+		})
 	}
 
 	locations := make([]int, 0, len(source))

solution_sequence_generator.go

@@ -5,7 +5,6 @@ package nextroute
 import (
 	"math/rand"
 	"slices"
-	"sync/atomic"
 )
 
 // SequenceGeneratorChannel generates all possible sequences of solution stops
@@ -29,54 +28,55 @@ func SequenceGeneratorChannel(
 	pu SolutionPlanUnit,
 	quit <-chan struct{},
 ) chan SolutionStops {
-	planUnit := pu.(*solutionPlanStopsUnitImpl)
-	solution := planUnit.solution()
-	maxSequences := int64(solution.Model().SequenceSampleSize())
-	solutionStops := planUnit.SolutionStops()
 	ch := make(chan SolutionStops)
 	go func() {
 		defer close(ch)
-		switch planUnit.ModelPlanStopsUnit().NumberOfStops() {
-		case 1:
-			ch <- solutionStops
-			return
-		default:
-			used := make([]bool, len(solutionStops))
-			inDegree := map[int]int{}
-			modelPlanUnit := planUnit.ModelPlanUnit().(*planMultipleStopsImpl)
-			dag := modelPlanUnit.dag.(*directedAcyclicGraphImpl)
-			for _, solutionStop := range solutionStops {
-				inDegree[solutionStop.ModelStop().Index()] = 0
-			}
-			for _, arc := range dag.arcs {
-				inDegree[arc.Destination().Index()]++
+		sequenceGeneratorSync(pu, func(solutionStops SolutionStops) {
+			select {
+			case <-quit:
+				return
+			case ch <- slices.Clone(solutionStops):
 			}
-
-			sequenceGenerator(
-				solutionStops,
-				make([]SolutionStop, 0, len(solutionStops)),
-				used,
-				inDegree,
-				dag,
-				solution.Random(),
-				&maxSequences,
-				func(solutionStops SolutionStops) {
-					select {
-					case <-quit:
-						return
-					case ch <- solutionStops:
-					}
-				},
-				-1,
-			)
-		}
+		})
 	}()
 
 	return ch
 }
 
-func sequenceGenerator(
-	stops, sequence SolutionStops,
+func sequenceGeneratorSync(pu SolutionPlanUnit, yield func(SolutionStops)) {
+	planUnit := pu.(*solutionPlanStopsUnitImpl)
+	solutionStops := planUnit.solutionStops
+	if planUnit.ModelPlanStopsUnit().NumberOfStops() == 1 {
+		yield(planUnit.SolutionStops())
+		return
+	}
+	solution := planUnit.solution()
+	maxSequences := int64(solution.Model().SequenceSampleSize())
+	nSolutionStops := len(solutionStops)
+	used := make([]bool, nSolutionStops)
+	inDegree := make(map[int]int, nSolutionStops)
+	modelPlanUnit := planUnit.ModelPlanUnit().(*planMultipleStopsImpl)
+	dag := modelPlanUnit.dag.(*directedAcyclicGraphImpl)
+	for _, arc := range dag.arcs {
+		inDegree[arc.Destination().Index()]++
+	}
+
+	recursiveSequenceGenerator(
+		solutionStops,
+		make([]SolutionStop, 0, nSolutionStops),
+		used,
+		inDegree,
+		dag,
+		solution.Random(),
+		&maxSequences,
+		yield,
+		-1,
+	)
+}
+
+func recursiveSequenceGenerator(
+	stops []SolutionStop,
+	sequence SolutionStops,
 	used []bool,
 	inDegree map[int]int,
 	dag DirectedAcyclicGraph,
@@ -85,21 +85,27 @@ func sequenceGenerator(
 	yield func(SolutionStops),
 	directSuccessor int,
 ) {
-	if len(sequence) == len(stops) {
-		if atomic.AddInt64(maxSequences, -1) >= 0 {
-			yield(slices.Clone(sequence))
+	if *maxSequences == 0 {
+		return
+	}
+	nStops := len(stops)
+	if len(sequence) == nStops {
+		*maxSequences--
+		if *maxSequences >= 0 {
+			yield(sequence)
 		}
 		return
 	}
 
-	stopOrder := random.Perm(len(stops))
+	stopOrder := random.Perm(nStops)
 
 	// we know the direct successor, so we move it to the front of the random
 	// sequence
 	if directSuccessor != -1 {
 		for _, stopIdx := range stopOrder {
 			if stops[stopIdx].Index() == directSuccessor {
-				stopOrder = []int{stopIdx}
+				stopOrder = stopOrder[:1]
+				stopOrder[0] = stopIdx
 				break
 			}
 		}
@@ -128,7 +134,9 @@ func sequenceGenerator(
 					}
 				}
 			}
-			sequenceGenerator(stops, append(sequence, stop), used, inDegree, dag, random, maxSequences, yield, directSuccessor)
+			recursiveSequenceGenerator(
+				stops, append(sequence, stop), used, inDegree, dag, random, maxSequences, yield, directSuccessor,
+			)
 			// reached the maximum number of sequences
 			if *maxSequences == 0 {
 				return

solution_vehicle.go

@@ -316,12 +316,10 @@ func (v SolutionVehicle) bestMovePlanMultipleStops(
 	preAllocatedMoveContainer *PreAllocatedMoveContainer,
 ) SolutionMove {
 	var bestMove SolutionMove = newNotExecutableSolutionMoveStops(planUnit)
-	quitSequenceGenerator := make(chan struct{})
-	defer close(quitSequenceGenerator)
-	for sequence := range SequenceGeneratorChannel(planUnit, quitSequenceGenerator) {
+	sequenceGeneratorSync(planUnit, func(sequence SolutionStops) {
 		newMove := v.bestMoveSequence(ctx, planUnit, sequence, preAllocatedMoveContainer)
 		bestMove = takeBestInPlace(bestMove, newMove)
-	}
+	})
 	return bestMove
 }