50312
The distributed program reliability analysis on ring-type topologies
Abstract Distributed computing system (DCS) has become very popular for its high fault-tolerance, potential for parallel processing, and better reliability performance. One of the important issues in the design of the DCS is the reliability performance. Distributed program reliability (DPR) is addressed to obtain this reliability measure. In this paper, we propose a polynomial-time algorithm for computing the DPR of ring topology and show that solving the DPR problem on a ring of trees topology is NP-hard. Scope and purpose The widespread use of distributed computing system is due to the price–performance revolution in microelectronics, the development of cost-effective and efficient communication subsets, the development of resource sharing software, and the increased user demands for communication, economical sharing of resources, and productivity. This article is concerned with the analysis of distributed program reliability on a ring-distributed computing system. The distributed program reliability is a useful measure for reliability evaluation of distributed computing system. The distributed program reliability analyses also give a good index for designing a high-reliability-performance-distributed computing system.
5909240
The Computational Complexity of the Reliability Problem on Distributed Systems
Abstract The reliability of a distributed program in a distributed computing system is the probability that a program which runs on multiple processing elements and needs to communicate with other processing elements for remote data files will be executed successfully. This reliability varies according to 1. (1) the topology of the distributed computing system 2. (2) the reliability of the communication links 3. (3) the data files and program distribution among processing elements and 4. (4) the data files required to execute a program. This paper shows that solving this reliability problem is NP-hard even when the distributed computing system is restricted to a series-parallel, a 2-tree, a tree, or a star structure.
9041268
Modeling ice dynamics as a thin-film Stefan problem
Large, 3D ice formations such as icicles exhibit a high degree of geometric and optical complexity. Modeling these features by hand can be a daunting task, so we present a novel physically-based algorithm for simulating this phenomenon. Solidification is usually posed as a so-called 'Stefan problem', but the problem in its classic form is inappropriate for simulating the ice typically found in a winter scene. We instead use the 'thin-film' variant of the Stefan problem to derive velocity equations for a level set simulation. However, due to the scales involved in the problem, even an adaptive grid level set solver is still insufficient to track the tip of an icicle. Therefore, we derive an analytical solution for the icicle tip and use it to correct the level set simulation. The results appear to be in agreement with experimental data. We also present a physically-based technique for modeling ripples along the ice surface that alleviates the need to explicitly track small-scale geometry. To our knowledge, our approach is the most complete model available, and produces complex visual phenomena that no previous method has been able to capture.
16198203
On Semantics of Reactive Rule-Based Systems
In this paper we address special issues which arise when the rule-based programming paradigm is emlployed in development of reactive real-time systems. We begin by presenting a rule-based language which has emerged while developing intelligent cruise control systems. We describe a naive operational semantics based on an an implemented inference engine, and explain why the semantics is not appropriate in safety-critical real-time contexts. We then deene a number of correct-ness criteria ensuring termination, consistency and determinism, based on a formal declarative semantics. However, the declarative semantics is non-constructive. In order to be able to build an implementation satisfying the correctness criteria, two alternative approaches are proposed. Both approaches build upon static checks of a rule-based program. In the rst approach some correctness criteria are met by accepting only stratiied programs after the static checks. In the second approach we accept programs which are correct with respect to a constructive semantics. For both approaches we present the analysis methods and soundness results with respect to the desired declarative semantics. Abstract In this paper we address special issues which arise when the rule-based programming paradigm is emlployed in development of reactive real-time systems. We begin by presenting a rule-based language which has emerged while developing intelligent cruise control systems. We describe a naive operational semantics based on an an implemented inference engine, and explain why the semantics is not appropriate in safety-critical real-time contexts. We then deene a number of correct-ness criteria ensuring termination, consistency and determinism, based on a formal declarative semantics. However, the declarative semantics is non-constructive. In order to be able to build an implementation satisfying the correctness criteria, two alternative approaches are proposed. Both approaches build upon static checks of a rule-based program. In the rst approach some correctness criteria are met by accepting only stratiied programs after the static checks. In the second approach we accept programs which are correct with respect to a constructive semantics. For both approaches we present the analysis methods and soundness results with respect to the desired declarative semantics.
5140837
Modeling hair using level-of-detail representations
We present a novel approach for modeling hair using level-of-detail representations. The set of representations include individual strands, hair clusters, and hair strips. They are represented using subdivision curves or surfaces, and have the same underlying base skeleton to maintain consistent high-level physical behavior when a transition between different levels-of detail occurs. This framework supports automatic simplification of dynamic simulation, collision detection, and graphical rendering of animated hair. It also offers flexibility to balance between the overall performance and visual quality, and can be used to model and render different hairstyles. We have used these level-of-detail representations to animate various hairstyles and obtained noticeable performance improvement, with little loss in visual quality.
5671330
Physically based animation and rendering of lightning
We present a physically-based method for animating and rendering lightning and other electric arcs. For the simulation, we present the dielectric breakdown model, an elegant formulation of electrical pattern formation. We then extend the model to animate a sustained, 'dancing' electrical arc, by using a simplified Helmholtz equation for propagating electromagnetic waves. For rendering, we use a convolution kernel to produce results competitive with Monte Carlo ray tracing. Lastly, we present user parameters for manipulation of the simulation patterns.
15734500
Fast Animation of Lightning Using an Adaptive Mesh
We present a fast method for simulating, animating, and rendering lightning using adaptive grids. The "dielectric breakdown model" is an elegant algorithm for electrical pattern formation that we extend to enable animation of lightning. The simulation can be slow, particularly in 3D, because it involves solving a large Poisson problem. Losasso et al. recently proposed an octree data structure for simulating water and smoke, and we show that this discretization can be applied to the problem of lightning simulation as well. However, implementing the incomplete Cholesky conjugate gradient (ICCG) solver for this problem can be daunting, so we provide an extensive discussion of implementation issues. ICCG solvers can usually be accelerated using "Eisenstat's trick," but the trick cannot be directly applied to the adaptive case. Fortunately, we show that an "almost incomplete Cholesky" factorization can be computed so that Eisenstat's trick can still be used. We then present a fast rendering method based on convolution that is competitive with Monte Carlo ray tracing but orders of magnitude faster, and we also show how to further improve the visual results using jittering