Catalytic space-efficient algorithms for Distance and Determinant

Abstract

Catalytic computation reuses potentially large but in-use space (or catalytic space) which must be restored to its initial contents while the clean space is small. This allows all problems in $\mathsf{NL}$ and even larger classes to be in catalytic logspace [Buhrman et al, STOC2014]. In [Chmel et al, CCC2026] the catalytic space for reachability was restricted to sublinear space (specifically, $n \big/ 2^{θ(\sqrt{\log n})}$ space) while remaining in polynomial time. This matches the non-catalytic bounds from [Barnes et al, SICOMP1998]. We extend the reachability bound to shortest distance, proving a simultaneous sublinear catalytic space and polynomial time bound (henceforth called, sublinear $\mathsf{CLP}$). This is the first simultaneous sublinear space and polynomial time bound for distance even without the catalytic discipline. Moreover, our bound works even for polynomially weighted graphs. Along the way we prove simultaneous near linear catalytic space ($\mathcal{O}(n\log^{O(1)}{n})$) and polynomial time bounds for the determinant. We also show some applications to planar matching problems. Our starting point was catalytic computation of reachability in directed graphs by [Cook-Pyne, ITCS2026]. [Edenhofer, arXiv:2602.21088] used it to give a tradeoff between catalytic and non-catalytic space, while [Chmel et al, CCC2026] compress the graph to a smaller graph preserving $s,t$-reachability to achieve a smaller space bound. All three can be modified to yield an algorithm for unweighted distance. Our contribution is to define an approximation to the walk polynomial in weighted graphs that allows us to infer weighted $s,t$-distance in sublinear $\mathsf{CLP}$. We do so by non-trivially combining elements from each of the above three papers.