A²utoLPBench: An Auto-Generated, Agent-Friendly LP Benchmark via Inverse-KKT Construction
Pith reviewed 2026-07-03 14:06 UTC · model grok-4.3
The pith
A generator builds linear programming word problems whose optimal solutions are known exactly by construction, with no solver or human label needed.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
By applying the inverse-KKT construction—selecting a feasible point together with its dual and writing down the linear program that makes that point optimal—the authors produce an unlimited stream of plain-text LP problems whose ground-truth solutions and objective values are correct by design rather than by external verification.
What carries the argument
Inverse-KKT construction: the step that derives an LP from a pre-chosen optimal primal-dual pair so optimality holds by algebraic identity.
If this is right
- Any number of fresh problems can be produced without repeating content across runs.
- Difficulty is adjustable in advance by choosing the dimensions (n, m) before generation.
- Scores remain comparable across independent batches because every answer is exact.
- Training-data leakage can be avoided by selecting seed ranges after any model cutoff date.
- The bundled Docker environment lets an agent run the full benchmark with a single command.
Where Pith is reading between the lines
- The same construction pattern could be tried for quadratic or integer programs where an inverse optimality condition is also available.
- Agents could be tested on streams of problems whose difficulty increases automatically during a single run.
- The generator could be paired with other modalities such as diagram-to-LP translation to measure cross-format robustness.
- Public leaderboards could adopt rolling seed windows so that reported scores stay valid even after models are retrained.
Load-bearing premise
Problems built this way match the structure and difficulty of real LP word problems that human users would actually pose to an agent.
What would settle it
Collect an independent set of human-written LP word problems, run the same agents on both sets, and check whether success rates or error patterns diverge sharply or whether the generated problems systematically differ in constraint density or variable scaling from the human set.
Figures
read the original abstract
Most LP-from-text benchmarks are static datasets of word problems written and labeled by hand. Once such a dataset is released, its size is fixed, its difficulty is fixed, and every problem can leak into the training data of future LLMs. We present \textbf{A$^{2}$utoLPBench}, a benchmark for testing LLM-driven agents on linear programming problems written in plain text. We first pick a feasible point and dual, then write down a problem for which that point is optimal and the objective value is known. The answer is known by construction, with no solver call and no human annotator. The evaluation environment bundles a reference solver-critic baseline and a Docker image whose usage instructions are written for an LLM-driven agent to read. With these in place, any agent can run the benchmark and get a calibrated score with one command. Because the benchmark is a generator rather than a fixed dataset, it has properties no fixed dataset can match: an unlimited supply of fresh problems, a difficulty knob set by $(n,m)$, ground-truth answers correct by construction, low LLM-side cost per problem relative to human authoring, repeatable scores across independent batches, and resistance to training-data leakage when fresh post-cutoff seed ranges are used.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript introduces A²utoLPBench, a generator-based benchmark for evaluating LLM-driven agents on linear programming problems expressed in plain text. The central method selects a primal feasible point x* and dual multipliers, then constructs the LP coefficients (c, A, b) such that the KKT conditions hold exactly at that point; because KKT conditions are necessary and sufficient for optimality in LPs, the objective value c^T x* is known to be optimal by construction without any solver call or human annotation. The benchmark supplies an unlimited stream of fresh instances whose difficulty is controlled by the pair (n, m), ships a Docker image with usage instructions written for agents, and includes a reference solver-critic baseline.
Significance. If the generated instances remain numerically stable and the construction is shown to produce non-degenerate problems, the approach supplies a scalable, leakage-resistant source of verifiable LP-from-text tasks that static human-authored datasets cannot match. The explicit use of KKT sufficiency to obtain ground truth without external solvers is a clear technical strength.
major comments (2)
- [§3] §3 (Inverse-KKT Construction): the manuscript must explicitly verify that the constructed matrix A always yields a feasible and bounded primal when a strictly feasible x* and feasible dual multipliers are chosen; otherwise the claim that every generated instance has a known finite optimum could fail for some random seeds.
- [§5] §5 (Evaluation Protocol): the paper reports no quantitative comparison between the distribution of coefficients or constraint densities in the generated instances and any existing LP-from-text corpus; without such statistics the claim that the benchmark meaningfully tests agents on realistic LP-from-text tasks remains unanchored.
minor comments (2)
- The abstract states that the Docker image 'usage instructions are written for an LLM-driven agent to read' but does not quote or describe the prompt template; this detail belongs in the methods section for reproducibility.
- [§2] Notation: the pair (n, m) is introduced as the difficulty knob but is never defined as the number of variables and constraints; add an explicit sentence in the first paragraph of §2.
Simulated Author's Rebuttal
We thank the referee for the positive assessment and the recommendation of minor revision. We address the two major comments point by point below.
read point-by-point responses
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Referee: [§3] §3 (Inverse-KKT Construction): the manuscript must explicitly verify that the constructed matrix A always yields a feasible and bounded primal when a strictly feasible x* and feasible dual multipliers are chosen; otherwise the claim that every generated instance has a known finite optimum could fail for some random seeds.
Authors: We agree that an explicit verification strengthens the presentation. By construction, primal feasibility holds because x* is chosen to strictly satisfy the inequality system that defines the feasible region (i.e., A x* ≤ b is enforced when b is set from the chosen x*). Boundedness of the primal follows directly from dual feasibility: the chosen dual multipliers satisfy the dual constraints, so weak duality supplies a finite upper bound on the primal objective. Because the KKT conditions are satisfied at x* and the problem is an LP, strong duality applies and the constructed instance necessarily possesses a finite optimum. In the revised manuscript we will insert a short paragraph in §3 making this argument explicit, together with a brief remark on the numerical safeguards already present in the generator code. revision: yes
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Referee: [§5] §5 (Evaluation Protocol): the paper reports no quantitative comparison between the distribution of coefficients or constraint densities in the generated instances and any existing LP-from-text corpus; without such statistics the claim that the benchmark meaningfully tests agents on realistic LP-from-text tasks remains unanchored.
Authors: We respectfully maintain that a distributional comparison to existing human-authored corpora is not required to support the benchmark’s claims. The central motivation of A²utoLPBench is to overcome the inherent limitations of static datasets—fixed size, potential training-data leakage, and lack of fresh instances—by supplying an unlimited, verifiable generator whose difficulty is controlled by the pair (n, m). The phrase “realistic LP-from-text tasks” refers to the requirement that agents must parse natural-language descriptions and produce correct mathematical formulations, which is the same capability tested by prior LP word-problem collections; it does not imply statistical equivalence of coefficient distributions. Adding such a comparison would not alter the benchmark’s primary advantages. We therefore do not plan to incorporate distributional statistics in the revision. revision: no
Circularity Check
No significant circularity detected
full rationale
The paper's central method explicitly selects a feasible primal point x* and dual multipliers first, then constructs LP coefficients (c, A, b) such that KKT conditions hold at that point; optimality of c^T x* follows directly from the known necessity and sufficiency of KKT for linear programs. This is a deliberate forward generative construction rather than any derivation, prediction, or fitted parameter that reduces to its own inputs. No self-citations, ansatzes, or uniqueness theorems are invoked as load-bearing steps for the ground-truth claim. The benchmark is therefore self-contained against external benchmarks with no reduction by construction.
Axiom & Free-Parameter Ledger
free parameters (1)
- problem size (n, m)
axioms (1)
- standard math KKT optimality conditions hold for linear programs
Reference graph
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the candidate code produced no output, so no final answer is provided
Empty output (item mamo_complex_46):the vanilla MiMo-V2.5 solver returned a code block whose execution produced no FINAL_ANSWER line; the candidate stdout was empty. The DeepSeek-V4 critic flagged this on iteration 1 (“the candidate code produced no output, so no final answer is provided”), the solver re-derived the formulation, and the second iteration p...
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[45]
the candidate enforces only one protein constraint and adds an unnecessary zero variable bound
Missing constraint (item mamo_complex_23):the problem statement listed two protein requirements (88g and 144g, modeled as a maximum constraint plus a minimum constraint). 19 The vanilla MiMo-V2.5 solver retained only the binding constraint and dropped the other. The DeepSeek-V4 critic disagreed twice with increasingly precise feedback (“the candidate enfo...
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total surplus (674) exceeds total deficit (398), making strict equality infeasible
Wrong constraint type (item mamo_complex_41):the vanilla MiMo-V2.5 solver modeled a flow-balance constraint asP out −P in =net when the problem allowed slack on either side. The DeepSeek-V4 critic flagged that “total surplus (674) exceeds total deficit (398), making strict equality infeasible”; the solver switched to inequality constraints and produced ϕ= 2114
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the model restricts shipments to direct transfers from surplus to deficit regions only, but the problem allows arbitrary transfers including indirect routes
Semantic gap (item mamo_complex_53):the vanilla MiMo-V2.5 solver assumed direct surplus-to-deficit transfers only, while the problem statement allowed indirect routes through intermediate regions. The DeepSeek-V4 critic caught the assumption explicitly (“the model restricts shipments to direct transfers from surplus to deficit regions only, but the proble...
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