945 research outputs found
Dichotomy Results for Fixed Point Counting in Boolean Dynamical Systems
We present dichotomy theorems regarding the computational complexity of
counting fixed points in boolean (discrete) dynamical systems, i.e., finite
discrete dynamical systems over the domain {0,1}. For a class F of boolean
functions and a class G of graphs, an (F,G)-system is a boolean dynamical
system with local transitions functions lying in F and graphs in G. We show
that, if local transition functions are given by lookup tables, then the
following complexity classification holds: Let F be a class of boolean
functions closed under superposition and let G be a graph class closed under
taking minors. If F contains all min-functions, all max-functions, or all
self-dual and monotone functions, and G contains all planar graphs, then it is
#P-complete to compute the number of fixed points in an (F,G)-system; otherwise
it is computable in polynomial time. We also prove a dichotomy theorem for the
case that local transition functions are given by formulas (over logical
bases). This theorem has a significantly more complicated structure than the
theorem for lookup tables. A corresponding theorem for boolean circuits
coincides with the theorem for formulas.Comment: 16 pages, extended abstract presented at 10th Italian Conference on
Theoretical Computer Science (ICTCS'2007
Reach Control on Simplices by Piecewise Affine Feedback
We study the reach control problem for affine systems on simplices, and the
focus is on cases when it is known that the problem is not solvable by
continuous state feedback. We examine from a geometric viewpoint the structural
properties of the system which make continuous state feedbacks fail. This
structure is encoded by so-called reach control indices, which are defined and
developed in the paper. Based on these indices, we propose a subdivision
algorithm and associated piecewise affine feedback. The method is shown to
solve the reach control problem in all remaining cases, assuming it is solvable
by open-loop controls
Dichotomy Results for Fixed-Point Existence Problems for Boolean Dynamical Systems
A complete classification of the computational complexity of the fixed-point
existence problem for boolean dynamical systems, i.e., finite discrete
dynamical systems over the domain {0, 1}, is presented. For function classes F
and graph classes G, an (F, G)-system is a boolean dynamical system such that
all local transition functions lie in F and the underlying graph lies in G. Let
F be a class of boolean functions which is closed under composition and let G
be a class of graphs which is closed under taking minors. The following
dichotomy theorems are shown: (1) If F contains the self-dual functions and G
contains the planar graphs then the fixed-point existence problem for (F,
G)-systems with local transition function given by truth-tables is NP-complete;
otherwise, it is decidable in polynomial time. (2) If F contains the self-dual
functions and G contains the graphs having vertex covers of size one then the
fixed-point existence problem for (F, G)-systems with local transition function
given by formulas or circuits is NP-complete; otherwise, it is decidable in
polynomial time.Comment: 17 pages; this version corrects an error/typo in the 2008/01/24
versio
Minimal Reachability is Hard To Approximate
In this note, we consider the problem of choosing which nodes of a linear
dynamical system should be actuated so that the state transfer from the
system's initial condition to a given final state is possible. Assuming a
standard complexity hypothesis, we show that this problem cannot be efficiently
solved or approximated in polynomial, or even quasi-polynomial, time
Singular Switched Systems in Discrete Time: Solvability, Observability, and Reachability Notions
Discrete-time singular (switched) systems, also known as(switched) difference-algebraic equations and discrete-time (switched)descriptor systems, have in general three solvability issues:inconsistent initial values, nonexistence ornonuniqueness of solutions, and noncausalities, which are generallynot desired in applications. To deal with those issues, newsolvability notions are proposed in the study, and the correspondingnecessary and sufficient conditions have been derived with the help of(strictly) index-1 notions. Furthermore, surrogate (switched)systems--ordinary (switched) systems that have equivalentbehavior--have also been established for solvable systems. Byutilizing those surrogate systems, fundamental analysis includingobservability, determinability, reachability, and controllability has also beencharacterized for singular linear (switched) systems. The solvabilitystudy has been extended to singular nonlinear (switched) systems, andmoreover, Lyapunov and incremental stability analyses have beenderived via single and switched Lyapunov function approaches
Reachability in Dynamical Systems with Rounding
We consider reachability in dynamical systems with discrete linear updates,
but with fixed digital precision, i.e., such that values of the system are
rounded at each step. Given a matrix , an
initial vector , a granularity and a
rounding operation projecting a vector of onto
another vector whose every entry is a multiple of , we are interested in the
behaviour of the orbit , i.e.,
the trajectory of a linear dynamical system in which the state is rounded after
each step. For arbitrary rounding functions with bounded effect, we show that
the complexity of deciding point-to-point reachability---whether a given target
belongs to ---is PSPACE-complete for
hyperbolic systems (when no eigenvalue of has modulus one). We also
establish decidability without any restrictions on eigenvalues for several
natural classes of rounding functions.Comment: To appear at FSTTCS'2
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