660 research outputs found
A Strategy Language for Testing Register Transfer Level Logic
The development of modern ICs requires a huge investment in RTL verification.
This is a reflection of brisk release schedules and the complexity of
contemporary chip designs. A major bottleneck to reaching verification closure
in such designs is the disproportionate effort expended in crafting directed
tests; which is necessary to reach those behaviors that other, more automated
testing methods fail to cover. This paper defines a novel language that can be
used to generate targeted stimuli for RTL logic and which mitigates the
complexities of writing directed tests. The main idea is to treat directed
testing as a meta-reasoning problem about simulation. Our language is both
formalized and prototyped as a proof-search strategy language in rewriting
logic. We illustrate its novel features and practical use with several
examples.published or submitted for publicatio
Worldsens: development and prototyping tools for application specific wireless sensors networks
International audienceIn this paper we present Worldsens, an integrated environment for development and rapid prototyping of wireless sensor network applications. Our environment relies on software simulation to help the designer during the whole development process. The refinement is done starting from the high level design choices down to the target code implementation, debug and performance analysis. In the early stages of the design, high level parameters, like for example the node sleep and activity periods, can be tuned using WS-Net, an event driven wireless network simulator. WSNet uses models for applications, protocols and radio medium communication with a parameterized accuracy. The second step of the sensor network application design takes place after the hardware implementation choices. This second step relies on the WSim cycle accurate hardware platform simulator. WSim is used to debug the application using the real target binary code. Precise performance evaluation, including real-time analysis at the interrupt level, are made possible at this low simulation level. WSim can be connected to WSNet, in place of the application and protocol models used during the high level simulation to achieve a full distributed application simulation. WSNet and WSNet+WSim allow a continuous refinement from high level estimations down to low level real-time validation. We illustrate the complete application design process using a real life demonstrator that implements a hello protocol for dynamic neighborhood discovery in a wireless sensor network environment
PARSEC: A Parametrized Simulation Engine for Ultra-High Energy Cosmic Ray Protons
We present a new simulation engine for fast generation of ultra-high energy
cosmic ray data based on parametrizations of common assumptions of UHECR origin
and propagation. Implemented are deflections in unstructured turbulent
extragalactic fields, energy losses for protons due to photo-pion production
and electron-pair production, as well as effects from the expansion of the
universe. Additionally, a simple model to estimate propagation effects from
iron nuclei is included. Deflections in galactic magnetic fields are included
using a matrix approach with precalculated lenses generated from backtracked
cosmic rays. The PARSEC program is based on object oriented programming
paradigms enabling users to extend the implemented models and is steerable with
a graphical user interface.Comment: 10 pages, 6 figures, accepted for publication in Astroparticle
Physic
Efficiency in nondeterministic control through non-forgetful backtracking
Journal ArticleNondeterministic (ND) control has long been used to express elegant solutions to complex search problems. Programs using ND control can be executed on conventional machines through a systematic examination of trial execution paths. Among the many approaches to the enumeration of these paths is backtracking, a depth-first search of the execution path tree. Despite its implementational advantages, backtracking in its purest form suffers from a "forgetfulness" of retracted execution subpaths. This can lead to exponential run-time on problems such as top-down parsing in which the same subproblem can reoccur in slightly different global contexts. This paper presents an alternative form of ND control implementation incorporating "non-forgetfulness" into backtracking. Reoccurrences of previously searched subgoals are detected and their net computational effects recreated on demand. Since each distinct goal is pursued at most once, search problems such as general top-down parsing run in polynomial time. Moreover, in contrast to an exhaustive, bottom-up approach, goals are only pursued if appropriate in some global context. A strategy for non-forgetful backtracking is outlined in terms of coroutines and ordinary backtracking. The description of an alternative implementation of this strategy using simple coroutines is referenced. Top-down parsing is used to illustrate the application of this technique in both linguistic appearance and execution effect. Finally, some directions for further research into generalizations of these results are suggested
Constraint-Based Qualitative Simulation
We consider qualitative simulation involving a finite set of qualitative
relations in presence of complete knowledge about their interrelationship. We
show how it can be naturally captured by means of constraints expressed in
temporal logic and constraint satisfaction problems. The constraints relate at
each stage the 'past' of a simulation with its 'future'. The benefit of this
approach is that it readily leads to an implementation based on constraint
technology that can be used to generate simulations and to answer queries about
them.Comment: 10 pages, to appear at the conference TIME 200
All-Solution Satisfiability Modulo Theories: applications, algorithms and benchmarks
keywords: Automated Test Generation;Bounded Model Checking;Quantitative Information Flow;Reliability Analysis;Satisfiability Modulo Theories;Symbolic ExecutionPasquale Malacaria's research was supported by grant EP/K032011/1
A simulation study on parallel backtracking with solution memoing for independent and-parallelism
Goal-level Independent and-parallelism (IAP) is exploited by scheduling for simultaneous execution two or more goals which will not interfere with each other at run time. This can be done safely even if such goals can produce multiple answers. The most successful IAP implementations to date have used recomputation of answers and sequentially ordered backtracking. While in principle simplifying the implementation, recomputation can be very inefficient if the granularity of the parallel goals is large enough and they produce several answers, while sequentially ordered backtracking limits parallelism. And, despite the expected simplification, the implementation of the classic schemes has proved to involve complex engineering, with the consequent difficulty for system maintenance and expansion, and still frequently run into the well-known trapped goal and garbage slot problems. This work presents ideas about an alternative parallel backtracking model for IAP and a simulation studio. The model features parallel out-of-order
backtracking and relies on answer memoization to reuse and combine answers. Whenever a parallel goal backtracks, its siblings also perform backtracking, but after storing the bindings generated by previous answers. The bindings are then reinstalled when combining answers. In order not to unnecessarily penalize forward execution, non-speculative and-parallel goals which have not been executed yet take precedence over sibling goals which could be backtracked over. Using a simulator, we show that this approach can bring significant performance advantages over classical approaches
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