34 research outputs found
Computability in the lattice of equivalence relations
We investigate computability in the lattice of equivalence relations on the
natural numbers. We mostly investigate whether the subsets of appropriately
defined subrecursive equivalence relations -for example the set of all
polynomial-time decidable equivalence relations- form sublattices of the
lattice.Comment: In Proceedings DICE-FOPARA 2017, arXiv:1704.0516
On Higher-Order Probabilistic Subrecursion
We study the expressive power of subrecursive probabilistic higher-order calculi. More specifically, we show that endowing a very expressive deterministic calculus like Godel's T with various forms of probabilistic choice operators may result in calculi which are not equivalent as for the class of distributions they give rise to, although they all guarantee almost-sure termination. Along the way, we introduce a probabilistic variation of the classic reducibility technique, and we prove that the simplest form of probabilistic choice leaves the expressive power of T essentially unaltered. The paper ends with some observations about the functional expressive power: expectedly, all the considered calculi capture the functions which T itself represents, at least when standard notions of observations are considered
The Parametric Complexity of Lossy Counter Machines
The reachability problem in lossy counter machines is the best-known ACKERMANN-complete problem and has been used to establish most of the ACKERMANN-hardness statements in the literature. This hides however a complexity gap when the number of counters is fixed. We close this gap and prove F_d-completeness for machines with d counters, which provides the first known uncontrived problems complete for the fast-growing complexity classes at levels 3 < d < omega. We develop for this an approach through antichain factorisations of bad sequences and analysing the length of controlled antichains
The prospects for mathematical logic in the twenty-first century
The four authors present their speculations about the future developments of
mathematical logic in the twenty-first century. The areas of recursion theory,
proof theory and logic for computer science, model theory, and set theory are
discussed independently.Comment: Association for Symbolic Logi
A tier-based typed programming language characterizing Feasible Functionals
The class of Basic Feasible Functionals BFF is the type-2 counterpart of
the class FP of type-1 functions computable in polynomial time. Several
characterizations have been suggested in the literature, but none of these
present a programming language with a type system guaranteeing this complexity
bound. We give a characterization of BFF based on an imperative language
with oracle calls using a tier-based type system whose inference is decidable.
Such a characterization should make it possible to link higher-order complexity
with programming theory. The low complexity (cubic in the size of the program)
of the type inference algorithm contrasts with the intractability of the
aforementioned methods and does not overly constrain the expressive power of
the language