feat: optimize lateral paths with SQP
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using System;
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using System.Threading;
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namespace MultiWheelC.TrajectoryPlanning.EMPlanner;
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/// <summary>Public lateral-planning entry point backed by the solver-neutral SQP optimizer.</summary>
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public sealed class LateralPlanner
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{
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private readonly SequentialConvexOptimizer _optimizer;
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public LateralPlanner(IQpSolver qpSolver)
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{
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_optimizer = new SequentialConvexOptimizer(qpSolver ?? throw new ArgumentNullException(nameof(qpSolver)));
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}
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public LateralPlanningResult Plan(LateralPlanningInput input, CancellationToken cancellationToken)
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{
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return _optimizer.Optimize(input, cancellationToken);
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}
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}
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@@ -0,0 +1,294 @@
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using System;
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using System.Collections.Generic;
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using System.Diagnostics;
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using System.Threading;
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namespace MultiWheelC.TrajectoryPlanning.EMPlanner;
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/// <summary>Runs bounded lateral SQP iterations and retains only independently validated candidates.</summary>
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public sealed class SequentialConvexOptimizer
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{
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private const double StationTolerance = 1e-12d;
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private readonly IQpSolver _qpSolver;
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private readonly LateralConstraintBuilder _constraintBuilder;
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private readonly LateralGeometryEvaluator _geometryEvaluator;
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private readonly LateralSolutionValidator _solutionValidator;
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public SequentialConvexOptimizer(IQpSolver qpSolver)
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: this(qpSolver, new LateralConstraintBuilder(new LateralObjectiveBuilder()), new LateralGeometryEvaluator(),
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new LateralSolutionValidator())
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{
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}
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internal SequentialConvexOptimizer(IQpSolver qpSolver, LateralConstraintBuilder constraintBuilder,
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LateralGeometryEvaluator geometryEvaluator, LateralSolutionValidator solutionValidator)
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{
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_qpSolver = qpSolver ?? throw new ArgumentNullException(nameof(qpSolver));
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_constraintBuilder = constraintBuilder ?? throw new ArgumentNullException(nameof(constraintBuilder));
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_geometryEvaluator = geometryEvaluator ?? throw new ArgumentNullException(nameof(geometryEvaluator));
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_solutionValidator = solutionValidator ?? throw new ArgumentNullException(nameof(solutionValidator));
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}
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public LateralPlanningResult Optimize(LateralPlanningInput input, CancellationToken cancellationToken)
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{
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if (input == null)
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return Failed(EmPlanningStatus.InvalidInput, "Lateral planning input is required.");
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if (!TryCreateSettings(input, out QpSolverSettings settings, out TimeSpan totalBudget, out double convergenceTolerance,
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out string configurationFailure))
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{
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return Failed(EmPlanningStatus.InvalidInput, configurationFailure);
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}
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LateralCandidate iterate = CreateInitialIterate(input);
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var warmStart = Array.Empty<double>();
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LateralPath lastValidatedPath = null;
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double previousObjective = 0d;
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bool hasPreviousObjective = false;
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var stopwatch = Stopwatch.StartNew();
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for (int iteration = 0; iteration < input.Configuration.Solver.MaximumOuterIterations; iteration++)
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{
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if (cancellationToken.IsCancellationRequested)
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return FallbackOrFailure(lastValidatedPath, EmPlanningStatus.Cancelled, "Lateral SQP was cancelled.");
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TimeSpan remainingBudget = totalBudget - stopwatch.Elapsed;
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if (remainingBudget <= TimeSpan.Zero)
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return FallbackOrFailure(lastValidatedPath, EmPlanningStatus.SolverTimedOut,
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"Lateral SQP exhausted its solve budget.");
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if (!_constraintBuilder.TryBuild(input, iterate, out QuadraticProgram problem, out string failureReason))
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{
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return FallbackOrFailure(lastValidatedPath, EmPlanningStatus.LateralInfeasible,
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"Lateral SQP constraints are infeasible: " + failureReason);
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}
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QpSolveResult solved = _qpSolver.Solve(problem,
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new QpSolverSettings(settings.MaximumIterations, settings.AbsoluteTolerance, settings.RelativeTolerance,
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remainingBudget, settings.EnableWarmStart, settings.EnablePolishing, settings.EnableNativeVerboseOutput),
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warmStart, cancellationToken);
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if (solved == null)
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return FallbackOrFailure(lastValidatedPath, EmPlanningStatus.Failed, "The lateral QP solver returned no result.");
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if (solved.Status == QpSolveStatus.TimeLimit || solved.Status == QpSolveStatus.MaximumIterations)
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{
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return FallbackOrFailure(lastValidatedPath, EmPlanningStatus.SolverTimedOut,
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"The lateral QP solver timed out: " + solved.Diagnostic);
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}
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if (solved.Status == QpSolveStatus.Cancelled)
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return FallbackOrFailure(lastValidatedPath, EmPlanningStatus.Cancelled,
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"The lateral QP solver was cancelled: " + solved.Diagnostic);
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if (solved.Status == QpSolveStatus.PrimalInfeasible || solved.Status == QpSolveStatus.DualInfeasible)
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{
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return FallbackOrFailure(lastValidatedPath, EmPlanningStatus.LateralInfeasible,
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"The lateral QP solver reported infeasibility: " + solved.Diagnostic);
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}
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if (solved.Status == QpSolveStatus.SolverUnavailable)
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return FallbackOrFailure(lastValidatedPath, EmPlanningStatus.SolverUnavailable,
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"The lateral QP solver is unavailable: " + solved.Diagnostic);
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if (solved.Status != QpSolveStatus.Solved && solved.Status != QpSolveStatus.SolvedInaccurate)
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{
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return FallbackOrFailure(lastValidatedPath, EmPlanningStatus.Failed,
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"The lateral QP solver failed: " + solved.Diagnostic);
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}
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if (solved.Status == QpSolveStatus.SolvedInaccurate && !HasStrictResiduals(solved, input.Configuration.Solver.StrictResidualTolerance))
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{
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continue;
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}
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if (!TryCreateCandidate(input.ReferenceStations, solved.Primal, out LateralCandidate candidate))
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continue;
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if (!_geometryEvaluator.TryEvaluate(input, candidate, out LateralPath evaluatedPath, out _))
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continue;
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if (!_solutionValidator.TryValidate(input, candidate, evaluatedPath, out LateralPath validatedPath, out _))
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continue;
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double maximumLateralChange = MaximumLateralChange(iterate, candidate);
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double relativeObjectiveImprovement = hasPreviousObjective
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? RelativeObjectiveImprovement(previousObjective, solved.Objective)
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: double.PositiveInfinity;
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lastValidatedPath = CopyPath(validatedPath);
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iterate = candidate;
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warmStart = CopyValues(solved.Primal);
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previousObjective = solved.Objective;
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hasPreviousObjective = true;
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if (maximumLateralChange <= convergenceTolerance && relativeObjectiveImprovement <= convergenceTolerance)
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return new LateralPlanningResult(EmPlanningStatus.Success, lastValidatedPath, string.Empty);
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}
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return lastValidatedPath == null
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? Failed(EmPlanningStatus.LateralInfeasible, "No independently validated lateral candidate was found.")
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: new LateralPlanningResult(EmPlanningStatus.Success, lastValidatedPath, string.Empty);
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}
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private static bool TryCreateSettings(LateralPlanningInput input, out QpSolverSettings settings, out TimeSpan totalBudget,
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out double convergenceTolerance, out string failureReason)
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{
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settings = null;
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totalBudget = TimeSpan.Zero;
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convergenceTolerance = 0d;
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failureReason = string.Empty;
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SolverConfiguration solver = input.Configuration.Solver;
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SchedulingConfiguration scheduling = input.Configuration.Scheduling;
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if (solver == null || scheduling == null || solver.MaximumOuterIterations <= 0 ||
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!IsPositiveFinite(solver.AbsoluteTolerance) || !IsPositiveFinite(solver.RelativeTolerance) ||
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!IsPositiveFinite(solver.StrictResidualTolerance) || !IsPositiveFinite(scheduling.SolverTimeoutSeconds))
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{
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failureReason = "The lateral SQP solver configuration is invalid.";
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return false;
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}
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try
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{
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totalBudget = TimeSpan.FromSeconds(scheduling.SolverTimeoutSeconds);
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settings = new QpSolverSettings(solver.MaximumOsqpIterations, solver.AbsoluteTolerance, solver.RelativeTolerance,
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totalBudget, solver.WarmStart, solver.Polish, solver.NativeVerbose);
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convergenceTolerance = solver.StrictResidualTolerance;
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return true;
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}
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catch (ArgumentException exception)
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{
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failureReason = exception.Message;
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return false;
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}
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}
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private static LateralCandidate CreateInitialIterate(LateralPlanningInput input)
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{
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int stationCount = input.ReferenceStations.Count;
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var l = new double[stationCount];
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var dl = new double[stationCount];
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var ddl = new double[stationCount];
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var dddl = new double[stationCount - 1];
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bool coversAllStations = input.PreviousTrajectorySeed.Count >= 2 &&
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input.PreviousTrajectorySeed[0].ReferenceS <= input.ReferenceStations[0] + StationTolerance &&
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input.PreviousTrajectorySeed[input.PreviousTrajectorySeed.Count - 1].ReferenceS >=
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input.ReferenceStations[stationCount - 1] - StationTolerance;
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for (int index = 0; index < stationCount; index++)
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{
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LateralInterval corridor = input.Corridor.Stations[index];
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l[index] = coversAllStations
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? InterpolateSeedL(input.PreviousTrajectorySeed, input.ReferenceStations[index])
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: Clamp(0d, corridor.MinimumL, corridor.MaximumL);
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}
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double startDenominator = 1d - input.StartProjection.ReferencePoint.GeometricCurvature *
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input.StartProjection.LateralOffset;
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l[0] = input.StartProjection.LateralOffset;
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dl[0] = startDenominator * Math.Tan(input.StartProjection.HeadingError);
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return new LateralCandidate(input.ReferenceStations, l, dl, ddl, dddl);
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}
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private static bool TryCreateCandidate(IReadOnlyList<double> stations, IReadOnlyList<double> primal,
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out LateralCandidate candidate)
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{
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candidate = null;
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if (primal == null)
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return false;
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try
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{
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var layout = new LateralVariableLayout(stations.Count);
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if (primal.Count != layout.VariableCount)
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return false;
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var l = new double[layout.StationCount];
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var dl = new double[layout.StationCount];
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var ddl = new double[layout.StationCount];
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var dddl = new double[layout.StationCount - 1];
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for (int index = 0; index < layout.StationCount; index++)
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{
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l[index] = primal[layout.L(index)];
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dl[index] = primal[layout.DL(index)];
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ddl[index] = primal[layout.DDL(index)];
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}
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for (int index = 0; index < dddl.Length; index++)
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dddl[index] = primal[layout.DDDL(index)];
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candidate = new LateralCandidate(stations, l, dl, ddl, dddl);
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return true;
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}
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catch (ArgumentException)
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{
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return false;
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}
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}
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private static bool HasStrictResiduals(QpSolveResult result, double tolerance)
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{
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return IsPositiveFinite(tolerance) && result.PrimalResidual >= 0d && result.DualResidual >= 0d &&
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result.PrimalResidual <= tolerance && result.DualResidual <= tolerance;
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}
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private static double MaximumLateralChange(LateralCandidate previous, LateralCandidate current)
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{
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double maximum = 0d;
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for (int index = 0; index < previous.L.Count; index++)
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maximum = Math.Max(maximum, Math.Abs(current.L[index] - previous.L[index]));
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return maximum;
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}
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private static double RelativeObjectiveImprovement(double previous, double current)
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{
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return Math.Abs(previous - current) / Math.Max(1d, Math.Abs(previous));
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}
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private static LateralPlanningResult FallbackOrFailure(LateralPath path, EmPlanningStatus failureStatus, string failureReason)
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{
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return path == null
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? Failed(failureStatus, failureReason)
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: new LateralPlanningResult(EmPlanningStatus.SuccessWithFallback, path, failureReason);
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}
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private static LateralPlanningResult Failed(EmPlanningStatus status, string reason)
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{
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return new LateralPlanningResult(status, null, reason);
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}
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private static LateralPath CopyPath(LateralPath source)
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{
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var points = new List<LateralPathPoint>(source.Points.Count);
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for (int index = 0; index < source.Points.Count; index++)
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{
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LateralPathPoint point = source.Points[index];
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points.Add(new LateralPathPoint(point.ReferenceS, point.PathS, point.L, point.DL, point.DDL, point.DDDL,
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point.X, point.Y, point.VehicleYaw, point.GeometricCurvature, point.VehicleCurvature,
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point.VehicleCurvatureDerivative));
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}
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return new LateralPath(points, true);
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}
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private static double[] CopyValues(IReadOnlyList<double> source)
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{
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var copy = new double[source.Count];
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for (int index = 0; index < source.Count; index++)
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copy[index] = source[index];
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return copy;
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}
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private static double InterpolateSeedL(IReadOnlyList<FrenetProjection> seed, double referenceS)
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{
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if (referenceS <= seed[0].ReferenceS)
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return seed[0].LateralOffset;
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for (int index = 1; index < seed.Count; index++)
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{
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if (referenceS <= seed[index].ReferenceS)
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{
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FrenetProjection lower = seed[index - 1];
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FrenetProjection upper = seed[index];
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double span = upper.ReferenceS - lower.ReferenceS;
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return span <= StationTolerance ? upper.LateralOffset : lower.LateralOffset +
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(upper.LateralOffset - lower.LateralOffset) * (referenceS - lower.ReferenceS) / span;
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}
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}
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return seed[seed.Count - 1].LateralOffset;
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}
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private static double Clamp(double value, double minimum, double maximum)
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{
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return Math.Max(minimum, Math.Min(maximum, value));
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}
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private static bool IsPositiveFinite(double value)
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{
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return !double.IsNaN(value) && !double.IsInfinity(value) && value > 0d;
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}
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}
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