28,270 research outputs found
The Countdown Problem
We systematically develop a functional program that solves the countdown problem, a numbers game in which the aim is to construct arithmetic expressions satisfying certain constraints. Starting from a formal specification of the problem, we present a simple but inefficient program that solves the problem, and prove that this program is correct. We then use program fusion to calculate an equivalent but more efficient program, which is then further improved by exploiting arithmetic properties
Phase transition in the Countdown problem
Here we present a combinatorial decision problem, inspired by the celebrated
quiz show called the countdown, that involves the computation of a given target
number T from a set of k randomly chosen integers along with a set of
arithmetic operations. We find that the probability of winning the game
evidences a threshold phenomenon that can be understood in the terms of an
algorithmic phase transition as a function of the set size k. Numerical
simulations show that such probability sharply transitions from zero to one at
some critical value of the control parameter, hence separating the algorithm's
parameter space in different phases. We also find that the system is maximally
efficient close to the critical point. We then derive analytical expressions
that match the numerical results for finite size and permit us to extrapolate
the behavior in the thermodynamic limit.Comment: Submitted for publicatio
THE EFFECT OF TRAFFIC LIGHT COUNTDOWN TIMER ON RED LIGHT RUNNING
Red-light running occurs when a driver enters an intersection after the traffic
signal has turned red. This situation then resolves to minor accidents and even lost of life.
Due to this critical problem, countdown timer is installed at the traffic light with a hope
to reduce the number of red light violent. However, the effect of this countdown timer to
the red light running in Malaysia is never been studied. This project evaluated the case in
detail and clarifies the findings. Two intersections are chosen which are with and without
countdown timer that representing an upstream and a downstream. Three stations are
identified, namely Station 1 (Intersection Balai Polis Pekan Baru), Station 2 (Intersection
Silibin) and Station 3 (Intersection Pasir Puteh). Traffic survey is conducted by leaving
the video camera at the right angle of the intersection to capture the intersection
movements. The recorded data are run through a television to project the visual and
traffic count is performed. The levels of service (LOS) of all the intersections involved in
the traffic survey are obtained through aaSIDRA software. The percentages of red light
running were derived from the data summary. The Chi-Square statistical analysis is
carried out from those percentages. The statistical analysis shows that the effect of
countdown timer on the number of red light running for Station 1 and Station 2, are not
significant but shown a significant effect on Station 3 at 95% confidence level. By
percentages, the road users who comply with the red light, cross the intersection during
amber and violate the red light are approximately the same for both intersections with and
without timer at Station 1. The percentages of road users who violate the red light and
cross the intersection during amber were approximately reduced by half at intersection
with countdown timer in Station 2. The percentage of compliance to the red light was
tremendously higher at the upstream compared downstream intersection in Station 3 case.
The percentages of road user who violate the red light and cross the intersection during
amber were remarkably lower at intersection with countdown timer. Results obtained
showed that the installation of countdown timer at the signalized intersection able to
reduce the number of red light running
Automatic programming of simulation models
The concepts of software engineering were used to improve the simulation modeling environment. Emphasis was placed on the application of an element of rapid prototyping, or automatic programming, to assist the modeler define the problem specification. Then, once the problem specification has been defined, an automatic code generator is used to write the simulation code. The following two domains were selected for evaluating the concepts of software engineering for discrete event simulation: manufacturing domain and a spacecraft countdown network sequence. The specific tasks were to: (1) define the software requirements for a graphical user interface to the Automatic Manufacturing Programming System (AMPS) system; (2) develop a graphical user interface for AMPS; and (3) compare the AMPS graphical interface with the AMPS interactive user interface
A Markovian event-based framework for stochastic spiking neural networks
In spiking neural networks, the information is conveyed by the spike times,
that depend on the intrinsic dynamics of each neuron, the input they receive
and on the connections between neurons. In this article we study the Markovian
nature of the sequence of spike times in stochastic neural networks, and in
particular the ability to deduce from a spike train the next spike time, and
therefore produce a description of the network activity only based on the spike
times regardless of the membrane potential process.
To study this question in a rigorous manner, we introduce and study an
event-based description of networks of noisy integrate-and-fire neurons, i.e.
that is based on the computation of the spike times. We show that the firing
times of the neurons in the networks constitute a Markov chain, whose
transition probability is related to the probability distribution of the
interspike interval of the neurons in the network. In the cases where the
Markovian model can be developed, the transition probability is explicitly
derived in such classical cases of neural networks as the linear
integrate-and-fire neuron models with excitatory and inhibitory interactions,
for different types of synapses, possibly featuring noisy synaptic integration,
transmission delays and absolute and relative refractory period. This covers
most of the cases that have been investigated in the event-based description of
spiking deterministic neural networks
Limit Your Consumption! Finding Bounds in Average-energy Games
Energy games are infinite two-player games played in weighted arenas with
quantitative objectives that restrict the consumption of a resource modeled by
the weights, e.g., a battery that is charged and drained. Typically, upper
and/or lower bounds on the battery capacity are part of the problem
description. Here, we consider the problem of determining upper bounds on the
average accumulated energy or on the capacity while satisfying a given lower
bound, i.e., we do not determine whether a given bound is sufficient to meet
the specification, but if there exists a sufficient bound to meet it.
In the classical setting with positive and negative weights, we show that the
problem of determining the existence of a sufficient bound on the long-run
average accumulated energy can be solved in doubly-exponential time. Then, we
consider recharge games: here, all weights are negative, but there are recharge
edges that recharge the energy to some fixed capacity. We show that bounding
the long-run average energy in such games is complete for exponential time.
Then, we consider the existential version of the problem, which turns out to be
solvable in polynomial time: here, we ask whether there is a recharge capacity
that allows the system player to win the game.
We conclude by studying tradeoffs between the memory needed to implement
strategies and the bounds they realize. We give an example showing that memory
can be traded for bounds and vice versa. Also, we show that increasing the
capacity allows to lower the average accumulated energy.Comment: In Proceedings QAPL'16, arXiv:1610.0769
- …