2026-07-24T06:34:48Z https://drops.dagstuhl.de/oai

oai:drops-oai.dagstuhl.de:17368 2024-03-06T10:59:34Z ddc:004 open_access

Computing Generalized Convolutions Faster Than Brute Force Esmer, Barış Can Kulik, Ariel Marx, Dániel Schepper, Philipp Węgrzycki, Karol Generalized Convolution Fast Fourier Transform Fast Subset Convolution In this paper, we consider a general notion of convolution. Let D be a finite domain and let Dⁿ be the set of n-length vectors (tuples) of D. Let f : D × D → D be a function and let ⊕_f be a coordinate-wise application of f. The f-Convolution of two functions g,h : Dⁿ → {-M,…,M} is (g ⊛_f h)(v) := ∑_{v_g,v_h ∈ D^n s.t. v = v_g ⊕_f v_h} g(v_g) ⋅ h(v_h) for every 𝐯 ∈ Dⁿ. This problem generalizes many fundamental convolutions such as Subset Convolution, XOR Product, Covering Product or Packing Product, etc. For arbitrary function f and domain D we can compute f-Convolution via brute-force enumeration in 𝒪̃(|D|^{2n} ⋅ polylog(M)) time. Our main result is an improvement over this naive algorithm. We show that f-Convolution can be computed exactly in 𝒪̃((c ⋅ |D|²)ⁿ ⋅ polylog(M)) for constant c := 5/6 when D has even cardinality. Our main observation is that a cyclic partition of a function f : D × D → D can be used to speed up the computation of f-Convolution, and we show that an appropriate cyclic partition exists for every f. Furthermore, we demonstrate that a single entry of the f-Convolution can be computed more efficiently. In this variant, we are given two functions g,h : Dⁿ → {-M,…,M} alongside with a vector 𝐯 ∈ Dⁿ and the task of the f-Query problem is to compute integer (g ⊛_f h)(𝐯). This is a generalization of the well-known Orthogonal Vectors problem. We show that f-Query can be computed in 𝒪̃(|D|^{(ω/2)n} ⋅ polylog(M)) time, where ω ∈ [2,2.373) is the exponent of currently fastest matrix multiplication algorithm. Schloss Dagstuhl – Leibniz-Zentrum für Informatik Barış Can Esmer and Ariel Kulik and Dániel Marx and Philipp Schepper and Karol Węgrzycki 2022 Is Part Of LIPIcs, Volume 249, 17th International Symposium on Parameterized and Exact Computation (IPEC 2022) InProceedings Text doc-type:ResearchArticle publishedVersion application/pdf doi:10.4230/LIPIcs.IPEC.2022.12 urn:nbn:de:0030-drops-173685 https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2022.12 eng https://creativecommons.org/licenses/by/4.0/legalcode