15,800 research outputs found

    Model checking learning agent systems using Promela with embedded C code and abstraction

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    As autonomous systems become more prevalent, methods for their verification will become more widely used. Model checking is a formal verification technique that can help ensure the safety of autonomous systems, but in most cases it cannot be applied by novices, or in its straight \off-the-shelf" form. In order to be more widely applicable it is crucial that more sophisticated techniques are used, and are presented in a way that is reproducible by engineers and verifiers alike. In this paper we demonstrate in detail two techniques that are used to increase the power of model checking using the model checker SPIN. The first of these is the use of embedded C code within Promela specifications, in order to accurately re ect robot movement. The second is to use abstraction together with a simulation relation to allow us to verify multiple environments simultaneously. We apply these techniques to a fairly simple system in which a robot moves about a fixed circular environment and learns to avoid obstacles. The learning algorithm is inspired by the way that insects learn to avoid obstacles in response to pain signals received from their antennae. Crucially, we prove that our abstraction is sound for our example system { a step that is often omitted but is vital if formal verification is to be widely accepted as a useful and meaningful approach

    Generalized Ramanujan Primes

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    In 1845, Bertrand conjectured that for all integers x≥2x\ge2, there exists at least one prime in (x/2,x](x/2, x]. This was proved by Chebyshev in 1860, and then generalized by Ramanujan in 1919. He showed that for any n≥1n\ge1, there is a (smallest) prime RnR_n such that π(x)−π(x/2)≥n\pi(x)- \pi(x/2) \ge n for all x≥Rnx \ge R_n. In 2009 Sondow called RnR_n the nnth Ramanujan prime and proved the asymptotic behavior Rn∼p2nR_n \sim p_{2n} (where pmp_m is the mmth prime). In the present paper, we generalize the interval of interest by introducing a parameter c∈(0,1)c \in (0,1) and defining the nnth cc-Ramanujan prime as the smallest integer Rc,nR_{c,n} such that for all x≥Rc,nx\ge R_{c,n}, there are at least nn primes in (cx,x](cx,x]. Using consequences of strengthened versions of the Prime Number Theorem, we prove that Rc,nR_{c,n} exists for all nn and all cc, that Rc,n∼pn1−cR_{c,n} \sim p_{\frac{n}{1-c}} as n→∞n\to\infty, and that the fraction of primes which are cc-Ramanujan converges to 1−c1-c. We then study finer questions related to their distribution among the primes, and see that the cc-Ramanujan primes display striking behavior, deviating significantly from a probabilistic model based on biased coin flipping; this was first observed by Sondow, Nicholson, and Noe in the case c=1/2c = 1/2. This model is related to the Cramer model, which correctly predicts many properties of primes on large scales, but has been shown to fail in some instances on smaller scales.Comment: 13 pages, 2 tables, to appear in the CANT 2011 Conference Proceedings. This is version 2.0. Changes: fixed typos, added references to OEIS sequences, and cited Shevelev's preprin

    Pass-Through And The Prediction Of Merger Price Effects

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    We use Monte Carlo experiments to study how pass-through can improve merger price predictions, focusing on the first order approximation (FOA) proposed in Jaffe and Weyl [2013]. FOA addresses the functional form misspecification that can exist in standard merger simulations. We find that the predictions of FOA are tightly distributed around the true price effects if pass-through is precise, but that measurement error in pass-through diminishes accuracy. As a comparison to FOA, we also study a methodology that uses pass-through to select among functional forms for use in simulation. This alternative also increases accuracy relative to standard merger simulation and proves more robust to measurement error

    The Mereology of Emergence

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    The debate about the ontological innocence of mereology has generally been framed as a debate about the plausibility of Universal Fusion. Ontologically loaded fusions must be more than the sum of their parts, and this seems to violate parsimony if fusion is universal. Less attention has been paid to the question of what sort of emergence mereological fusions must exhibit if they are irreducible to their parts. The philosophy of science literature provides several models of such strong emergence. Examining those models suggests that the difficulty with emergent fusions has at least as much to do with extensionality as it does with Universal Fusion. Some accounts of emergence fail to ensure irreducibility when combined with extensional mereologies. The most promising model for the strong emergence of ontologically loaded fusions fails to validate Anti-Symmetry, which naturally leads to failures of extensionality. These results suggest that the focus on Universal Fusion may have been misplaced

    Not Another Brick in the Wall: an Extensional Mereology for Potential Parts

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    Part is not a univocal term. Uses of parthood and composition that do not obey any supplementation principle have a long philosophical tradition and strong support from contemporary physics. We call such uses potential parts. This paper first shows why potential parts are important and incompatible with supplementation, then provides a formal mereology for such parts inspired by the path-integral approach to quantum electrodynamics

    The Gift

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