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Local Search

Local-search acceptors, foragers, move selectors, and score-level annealing.

Local search repeatedly generates candidate moves, scores them, accepts or rejects them, and commits one accepted candidate. It is the normal improvement phase after construction.

[[phases]]
type = "local_search"

[phases.acceptor]
type = "late_acceptance"
late_acceptance_size = 400

[phases.forager]
type = "accepted_count"
limit = 4

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

Acceptor

The acceptor decides whether a scored candidate can be accepted.

Acceptor Use
hill_climbing accept only improving moves
simulated_annealing allow controlled regressions while cooling
tabu_search avoid recently visited entities, values, or moves
late_acceptance compare against a historical score window
great_deluge compare against a decaying score boundary
step_counting_hill_climbing hold a boundary for a fixed step interval
diversified_late_acceptance late acceptance with diversification pressure

Score-Level Simulated Annealing

Simulated annealing supports per-score-level temperatures and hard-regression policy.

[phases.acceptor]
type = "simulated_annealing"
level_temperatures = [5.0, 500.0]
hard_regression_policy = "temperature_controlled"

[phases.acceptor.calibration]
sample_size = 64
target_acceptance_probability = 0.75
fallback_temperature = 2.0

level_temperatures are ordered from highest-priority score level to lowest-priority score level. hard_regression_policy decides whether hard-score regressions can be temperature-controlled or are never accepted.

Forager

The forager decides which accepted candidate is committed.

[phases.forager]
type = "accepted_count"
limit = 4

The accepted-count forager stops the current selector step after collecting limit accepted candidates, then picks the best candidate inside that finite horizon. It is the default for broad stock models because it lets streaming selectors improve incumbents under short budgets. Use best_score when you intentionally want a full-neighborhood greedy scan, and use limited_neighborhood when a selector itself needs a hard pre-scoring cap.

Move Selector

Move selection lives under [phases.move_selector].

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

[[phases.move_selector.selectors]]
type = "change_move_selector"
value_candidate_limit = 32

[[phases.move_selector.selectors]]
type = "swap_move_selector"

For selector details, start with Moves.

Union selectors can use sequential, round_robin, rotating_round_robin, or stratified_random selection order. The current stock defaults use fair ordering for broad unions so no child neighborhood owns the prefix indefinitely.

Assignment-backed grouped scalar selectors are regular local-search selectors. Use them when a model-owned ScalarGroup::assignment(...) should repair uncovered required nullable slots, capacity conflicts, bounded reassignments, same-sequence run gaps, value-window swaps, block reassignments, optional occupant releases, or value rotations:

[phases.move_selector]
type = "grouped_scalar_move_selector"
group_name = "required_shift_assignment"
max_moves_per_step = 64
require_hard_improvement = true

Telemetry

Retained status and events preserve exact generated, evaluated, accepted, not-doable, acceptor-rejected, forager-ignored, hard-delta, conflict-repair, and construction-slot counters plus generation and evaluation durations. Per-move-label telemetry reports generated, evaluated, accepted, applied, not-doable, acceptor-rejected, forager-ignored, score-improving, score-equal, score-worse, rejected-improving, and applied score-improvement totals. The bounded applied-move trace records the selected candidate index, per-step generated/evaluated/accepted/ignored counts, score delta, and hard feasibility before and after the applied move. Displayed moves/s is a human-facing derived value.

Variable Neighborhood Descent

VND is configured as local_search_type = "variable_neighborhood_descent" on a local-search phase. It uses ordered neighborhoods and does not combine with acceptor, forager, or move_selector in the same phase.

[[phases]]
type = "local_search"
local_search_type = "variable_neighborhood_descent"

[[phases.neighborhoods]]
type = "change_move_selector"
variable_name = "employee_idx"

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

See Also