Maintained Prefix Primal Feasibility
ProvedPrimalDual.buchbinder_naor_primal_feasible_throughConsider the normalized Buchbinder–Naor load-balancing algorithm after a successful prefix: it has processed the first jobs and its failure marker is unset. Then the current machine weights and job slacks form a feasible solution of the covering primal restricted to those jobs: all coordinates are nonnegative, and
for every eligible pair with .
This is the maintained primal feasibility from Theorem 8.1, Claim (2), of the source. Together with the exact primal-objective identity and weak duality, it produces the failure certificate that drives the mission's final theorem.
Formalization Note Feasibility is stated for the prefix linear program whose constraints are exactly the eligible pairs revealed so far; the slack coordinates of jobs that have not yet arrived are retained (at value ) and are subject only to nonnegativity.
import Definitions.Def_pd_unrelated_machines
namespace PrimalDual
/--
After every successful prefix, the online load-balancing updates give a feasible covering
solution for exactly the eligible constraints revealed in that prefix.
-/
theorem buchbinder_naor_primal_feasible_through
{jobs machines : ℕ} (I : UnrelatedMachines.Instance jobs machines)
(k : ℕ) (hk : k ≤ jobs)
(hNoFailure : (I.runPrefix k).failedAt = none) :
I.PrimalFeasibleThrough k (I.runPrefix k) := by
sorry
end PrimalDualRead-back
What the Lean code literally says, in plain math · gpt-5
For all , write , with ; for every instance consisting of a proof , a load function , and proofs for every and ; and for every with , let be the state obtained by starting with weights , assignments , slacks , dual entries , and failure marker , and then recursively processing the first members of the list . On arrival of , a state whose failure marker is already is left unchanged; otherwise let , and if or there exists with , change only the failure marker to ; if neither condition holds, compute the optional machine returned by taking an argmin of over the naturally sorted list of , changing only the failure marker to if this option is , while if it is , with and , replace by , by , by , and by , leave every other coordinate unchanged, and set the failure marker to . The theorem assumes that the component of this particular state , whose type is , equals , and asserts that all primal coordinates determined by are nonnegative—namely for every and for every , including jobs with index at least —and that for every and satisfying both and , the covering inequality holds; no covering inequality is quantified for an ineligible pair with or for a job with . When , no arrival is processed, the failure premise holds for the initial state, the covering-inequality quantifier is empty, and only nonnegativity of all initial machine weights and all job slacks remains; when , the hypothesis forces , all job and covering quantifiers are empty, but and nonnegativity of the machine weights remain; admits no such instance because an instance contains a proof ; and values , or prefix states whose failure marker is not , do not satisfy the theorem’s hypotheses.
Confirmed by the mission captain (proposal self-audit).