206929044
Comparison of structural formalisms for modeling large Markov models
Summary form only given. Stochastic automata networks and generalized stochastic Petri nets are the main formalisms used to model complex Markov systems in a structured "Kronecker" approach. We compare them on a suite of examples using two tools, PEPS and SMART.
229363
A Pattern Recognition Approach for Speculative Firing Prediction in Distributed Saturation State-Space Generation
The saturation strategy for symbolic state-space generation is particularly effective for globally-asynchronous locally-synchronous systems. A distributed version of saturation, SaturationNOW, uses the overall memory available on a network of workstations to effectively spread the memory load, but its execution is essentially sequential. To achieve true parallelism, we explore a speculative firing prediction, where idle workstations work on predicted future event firing requests. A naive approach where all possible firings may be explored a priori, given enough idle time, can result in excessive memory requirements. Thus, we introduce a history-based approach for firing prediction that recognizes firing patterns and explores only firings conforming to these patterns. Experiments show that our heuristic improves the runtime and has a small memory overhead.
6519527
A dynamic firing speculation to speedup distributed symbolic state-space generation
The saturation strategy for symbolic state-space generation is very effective for globally-asynchronous locally-synchronous discrete-state systems. Its inherently sequential nature, however, makes it difficult to parallelize on a NOW. An initial attempt that utilizes idle workstations to recognize event firing patterns and then speculatively compute firings conforming to these patterns is at times effective but can introduce large memory overheads. We suggest an implicit method to encode the firing history of decision diagram nodes, where patterns can be shared by nodes. By preserving the actual firing history efficiently and effectively, the speculation is more informed. Experiments show that our implicit encoding method not only reduces the memory requirements but also enables dynamic speculation schemes that further improve runtime
6697965
A Fine-Grained Fullness-Guided Chaining Heuristic for Symbolic Reachability Analysis
Chaining can reduce the number of iterations required for symbolic state-space generation and model-checking, especially in Petri nets and similar asynchronous systems, but requires considerable insight and is limited to a static ordering of the events in the high-level model. We introduce a two-step approach that is instead fine-grained and dynamically applied to the decision diagrams nodes. The first step, based on a precedence relation, is guaranteed to improve convergence, while the second one, based on a notion of node fullness, is heuristic. We apply our approach to traditional breadth-first and saturation state-space generation, and show that it is effective in both cases.
17772071
Large 2P3-free graphs with bounded degree
Abstract Let ex ∗ ( D ; H ) be the maximum number of edges in a connected graph with maximum degree D and no induced subgraph H ; this is finite if and only if H is a disjoint union of paths. If the largest component of such an H has order m , then ex ∗ (D; H) = O (D 2 ex ∗ (D; P m )) . Constructively, ex ∗ (D;qP m ) = Θ( g D 2 ex ∗ (D;P m )) if q >1 and m > 2( Θ ( gD 2 ) if m = 2). For H = 2 P 3 (and D ⩾ 8), the maximum number of edges is 1 8 [D 4 + D 3 + D 2 + 6D] if D is even and 1 8 [D 4 + D 3 + 2D 2 + 3D + 1 ] if D is odd, achieved by a unique extremal graph.
92691
A Formal Approach to Managing Design Processes
To capture market opportunities, competition within the microelectronics industry demands ever-faster product development, which means ever-shorter design cycles. Shorter design cycles can be achieved by carefully managing the design process during rapid prototyping. Careful management is important because the design process must be (1) adjusted to accommodate constraints such as product performance and design time, and (2) frequently updated to take advantage of new design tools and methodologies. Traditionally, designers have used whatever tools seemed convenient to them at the time, which has made it virtually impossible to determine what methodology was used to produce a given design. These problems can be avoided through design methodology management, which ensures that appropriate tools are selected and executed in the appropriate sequence. Effective design management requires an environment equipped with a formal representation of supported design processes and tools, and an execution environment that helps designers select and execute an appropriate design process. We propose a methodology management system that provides this functionality. >