Scalar Move Selectors

Scalar selectors operate on non-list planning variables. They are the right starting point for assignment, bin packing, staffing, matching, and other models where an entity owns one or more scalar decision fields.

Baseline Selectors

change_move_selector

Changes one scalar planning variable on one entity to a candidate value.

[phases.move_selector]
type = "change_move_selector"
variable_name = "employee_idx"
value_candidate_limit = 32

Use value_candidate_limit when the model exposes a large value range and the selector should retain a bounded candidate set.

swap_move_selector

Swaps one scalar planning variable between two entities. Use it when preserving the multiset of assigned values matters or pair exchanges repair a schedule more cheaply than assigning from scratch.

[phases.move_selector]
type = "swap_move_selector"
variable_name = "employee_idx"

Nearby Scalar Selectors

Nearby scalar selectors require model-declared candidate hooks on the matching #[planning_variable]: nearby_value_candidates for change moves and nearby_entity_candidates for swap moves. Distance meters rank or filter those bounded candidates; they do not discover candidates by themselves.

nearby_change_move_selector

[phases.move_selector]
type = "nearby_change_move_selector"
variable_name = "employee_idx"
max_nearby = 20

nearby_swap_move_selector

[phases.move_selector]
type = "nearby_swap_move_selector"
variable_name = "employee_idx"
max_nearby = 20

Pillar Selectors

Pillar selectors operate on deterministic groups of entities that currently share a compatible value.

[phases.move_selector]
type = "pillar_change_move_selector"
variable_name = "team_idx"
value_candidate_limit = 16

Ruin/Recreate

ruin_recreate_move_selector clears a bounded set of scalar assignments and recreates them with a configured value source. Use it to escape local optima in scalar models where several assignments need to move together before the score improves.

[phases.move_selector]
type = "ruin_recreate_move_selector"
variable_name = "employee_idx"
ruin_size = 8
value_candidate_limit = 32

Grouped Scalar

Use grouped scalar selectors when the legal decision changes several nullable scalar variables at once. The model provides a named scalar group; construction and local search both select that group by name.

[[phases]]
type = "construction_heuristic"
construction_heuristic_type = "first_fit"
group_name = "task_operator_assignment"
value_candidate_limit = 32
group_candidate_limit = 128

[[phases]]
type = "local_search"

[phases.move_selector]
type = "grouped_scalar_move_selector"
group_name = "task_operator_assignment"
max_moves_per_step = 256
require_hard_improvement = true

The underlying CompoundScalarMove applies multiple scalar edits atomically with exact undo, affected-entity reporting, tabu identity, duplicate filtering, not-doable filtering, and hard-delta handling.

Conflict Repair

Conflict-repair selectors build repair candidates from configured scoring matches. Use them when the model can explain how to repair a specific constraint match without fake variables or relaxed hard constraints.

[phases.move_selector]
type = "compound_conflict_repair_move_selector"
constraints = ["schedule/no_overlapping_operator_assignment"]
max_matches_per_step = 16
max_repairs_per_match = 32
max_moves_per_step = 256
require_hard_improvement = true

Available selectors:

Constraint keys match exact scoring metadata. Use ConstraintRef::full_name() for package-qualified constraints and the short name for package-less constraints.

Move Types

See Also

• List Move Selectors - selectors for ordered route and sequence variables
• Composite Move Selectors - union, cartesian, and limited neighborhoods