x.com/konstiwohlwend/status/2107872422825537599
1 correction found
To make the proof simpler, they use absurd safety bounds like 2^50 that are entirely arbitrary.
This misdescribes why the published exponents look 'ugly.' In the cited papers, those exponents are the actual theorem or abstract bounds proved for all input sizes/asymptotically, not artifacts of restricting the proof to some arbitrary cutoff like 2^50.
Full reasoning
The available primary sources for the two examples being discussed do not present their headline exponents as arbitrary finite cutoffs.
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In OpenAI's Integer multiplication below n log n source, the main theorem says there is a machine that computes the exact product "for every n >= 1" with worst-case running time
O(n (lg n)^(1-κ)), whereκ = 2^-182. The same introduction adds: "The bound is asymptotic through all input lengths." It also explains where the power saving comes from: "This strict inequality is the source of the power saving." That is, the tiny exponent is part of the proved asymptotic theorem, not a byproduct of only proving the result above an arbitrary threshold. -
In Alman and Vassilevska Williams' 3SUM/APSP paper, the abstract explicitly states the proven running times as
O(n^1.9992)for 3SUM andO(n^2.9995)for APSP, and traces them to a thin-matrix-product result with complexityO(N^2 / D^0.063). Again, the paper presents these as the actual asymptotic bounds it proves, not as placeholders created by an arbitrary safety cutoff.
So while it may be fair to speculate that later work could tighten these exponents, the claim that the published bounds come from "absurd safety bounds like 2^50 that are entirely arbitrary" is contradicted by the papers' own theorem/abstract statements and explanations of where the exponents come from.
2 sources
- OpenAI math: Integer multiplication below n log n — introduction source
There is one deterministic Turing machine ... that computes this exact product for every n >= 1 ... T_A(n)=O(n(lg n)^{1-kappa}), kappa = 2^{-182}. ... The bound is asymptotic through all input lengths. ... This strict inequality is the source of the power saving.
- Truly Subquadratic 3SUM and Truly Subcubic APSP via Triangles in Sparse Lopsided Graphs
Abstract: we show how to deterministically solve 3SUM ... in O(n^{1.9992}) time and APSP ... in O(n^{2.9995}) time. ... We compute the entries ... in O(N^2/D^{0.063}) operations.