The Condition-Number Barrier in Sparse Least Squares

Honghao Lin, Vahab Mirrokni, David P. Woodruff

Assuming the randomized rational-weighted exact-volume Small-Set Expansion Hypothesis, no randomized polynomial-time algorithm can guarantee both additive ε accuracy in rational sparse least squares and support O(k κₛ₊ₖ^(1−γ)) for any fixed γ∈(0,1]. The hard matrices have full column rank and at most two nonzeros per row.

Sources for this record

What was already known

Axiotis and Sviridenko obtained O(kκ) support bounds and asked whether the condition-number exponent could be improved. Earlier obstructions applied to particular algorithms, not all randomized polynomial-time methods.

AI involvement AI-autonomous

Lin, Mirrokni and Woodruff say a fully automated Gemini-based system first obtained the proof. They verified it, edited the paper and explain the graph-to-regression reduction.

The abstract and acknowledgements explicitly say a fully automated Gemini-based system first obtained the proof; no initial human mathematical step is identified.

Importance Notable

Under the stated hypothesis, extends an algorithm-specific barrier to all randomized polynomial-time sparse least-squares algorithms.

Limitations

The conclusion is conditional on the exact-volume SSE hypothesis and specific to least squares; it is not an unconditional barrier for all sparse convex objectives.

Technical verification Formal (human)

The three named human authors report verifying the complete proof of the conditional theorem before editing the final version. This is a source-reported author check, not one reproduced here; it does not verify the SSE hypothesis itself.

Formal checking

Human verification of the model-origin proof and editing of the final mathematical presentation

Checker
Honghao Lin, Vahab Mirrokni and David P. Woodruff, author-reviewers
Scope
Theorem 1.1's conditional sparse-least-squares condition-number lower bound
Basis
Reported by the linked checker
Evidence source

Checking a formal statement does not establish that it matches the original problem.

Human understanding Full

The named authors present a detailed explanation of the reduction and its exact-volume soundness step in Sections 1.2 and 4, and say they verified and clarified the proof. No specific central step is identified as unexplained.

Correction and publication history

2026-10-18 · publication

Under the stated hypothesis, extends an algorithm-specific barrier to all randomized polynomial-time sparse least-squares algorithms.

Read this published revision