List Move Selectors

List selectors operate on ordered list planning variables. They are the normal surface for vehicle routing, machine sequences, visit ordering, task queues, and other domains where position matters.

The runtime compiler validates the required list operations and metadata before the phase starts. Dynamic lists declare set, whole-row replace, reverse, and atomic sublist capabilities explicitly; an absent operation rejects a selector that needs it instead of being emulated from weaker mutations. Route, precedence, distance, ownership, and savings bundles are validated the same way.

Every concrete leaf can also choose original, seeded random, shuffled, sorted, or probabilistic order. Sorted and probabilistic leaves require a registered named candidate metric; omitted stock leaves use seeded random order.

Baseline Route Selectors

For most route or sequence models, start with nearby relocation, nearby swap, and reverse:

[phases.move_selector]
type = "union_move_selector"
selection_order = "round_robin"

[[phases.move_selector.selectors]]
type = "nearby_list_change_move_selector"
variable_name = "visits"
max_nearby = 16

[[phases.move_selector.selectors]]
type = "nearby_list_swap_move_selector"
variable_name = "visits"
max_nearby = 16

[[phases.move_selector.selectors]]
type = "list_reverse_move_selector"
variable_name = "visits"

Relocation And Swap

[phases.move_selector]
type = "nearby_list_change_move_selector"
variable_name = "visits"
max_nearby = 20

Nearby list selectors use list distance meters and stable tie ordering so seeded local search remains reproducible.

Sublist Selectors

Sublist selectors move or swap contiguous list segments. They are useful when a run of adjacent visits or tasks should stay together while moving elsewhere.

[phases.move_selector]
type = "sublist_change_move_selector"
variable_name = "visits"
max_sublist_size = 4

Permutation and Precedence

list_permute_move_selector permutes a contiguous window within one list. Use it when small reorderings matter but full k-opt routing semantics are not the right model.

[phases.move_selector]
type = "list_permute_move_selector"
variable_name = "operations"
min_window_size = 2
max_window_size = 5

list_precedence_move_selector is for list variables that expose precedence_duration_fn and precedence_successors_fn through #[planning_list_variable]. It generates critical-path, singleton critical-node, and critical-sublist support moves for precedence makespan models, while normal list change, swap, reverse, sublist, ruin, and k-opt selectors use the same precedence graph to reject cycle-forming same-route candidates.

[phases.move_selector]
type = "list_precedence_move_selector"
entity_class = "Route"
variable_name = "operations"

Route Improvement

list_reverse_move_selector

Reverses a contiguous segment. Use it as the basic 2-opt style improvement for routes and ordered sequences.

[phases.move_selector]
type = "list_reverse_move_selector"
variable_name = "visits"

k_opt_move_selector

Performs K-opt route reconnection for routing-style list variables.

[phases.move_selector]
type = "k_opt_move_selector"
variable_name = "visits"
k = 3

K-opt improvement uses the route-local hook bundle declared on #[planning_list_variable]. Stock CVRP lists can use domain = "cvrp"; that profile wires strict solverforge::cvrp::route_hooks so k-opt rejects candidate routes that violate stock capacity, time-window feasibility, or reachable-leg requirements. Stock distance hooks clamp unreachable or extreme route distances into the solver’s scoring domain instead of panicking or overflowing. Custom route domains can wire route_hooks explicitly. That module exports get, set, depot, distance, and feasible, and the owner argument is part of the contract: distance and feasibility should be evaluated in the vehicle, route, or machine context that will own the candidate route. Clarke-Wright construction stays on the separate savings_hooks module plus optional savings_metric_class_fn, so construction savings can share a metric class without collapsing route-local assignment semantics.

List Ruin

list_ruin_move_selector removes a bounded number of list elements and reinserts them. Use it for large-neighborhood search when small route edits are not enough.

[phases.move_selector]
type = "list_ruin_move_selector"
variable_name = "visits"
ruin_size = 8

The current runtime skips empty owners during list-ruin sampling, so empty routes or sequences do not consume ruin attempts.

Move Types

See Also

• List Variables - modeling ordered planning variables
• Composite Move Selectors - combining list and scalar neighborhoods