18,289 research outputs found
Partial Order Reduction for Security Protocols
Security protocols are concurrent processes that communicate using
cryptography with the aim of achieving various security properties. Recent work
on their formal verification has brought procedures and tools for deciding
trace equivalence properties (e.g., anonymity, unlinkability, vote secrecy) for
a bounded number of sessions. However, these procedures are based on a naive
symbolic exploration of all traces of the considered processes which,
unsurprisingly, greatly limits the scalability and practical impact of the
verification tools.
In this paper, we overcome this difficulty by developing partial order
reduction techniques for the verification of security protocols. We provide
reduced transition systems that optimally eliminate redundant traces, and which
are adequate for model-checking trace equivalence properties of protocols by
means of symbolic execution. We have implemented our reductions in the tool
Apte, and demonstrated that it achieves the expected speedup on various
protocols
Apollo experience report: Command and service module sequential events control subsystem
The Apollo command and service module sequential events control subsystem is described, with particular emphasis on the major systems and component problems and solutions. The subsystem requirements, design, and development and the test and flight history of the hardware are discussed. Recommendations to avoid similar problems on future programs are outlined
Folding Transformation Rules for Constraint Logic Programs
We consider the folding transformation rule for constraint
logic programs. We propose an algorithm for applying the folding rule in the case where the constraints are linear equations and inequations over the rational or the real numbers. Basically, our algorithm consists in reducing a rule application to the solution of one or more systems
of linear equations and inequations. We also introduce two variants of the folding transformation rule. The first variant combines the folding rule with the clause splitting rule, and the second variant eliminates the existential variables of a clause, that is, those variables which occur in the body of the clause and not in its head. Finally, we present the algorithms for applying these variants of the folding rule
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Software safety : a definition and some preliminary thoughts
Software safety is the subject of a research project in its initial stages at the University of California Irvine. This research deals with critical real-time software where the cost of an error is high, e.g. human life. In this paper software techniques having a bearing on safety are described and evaluated. Initial definitions of software safety concepts are presented along with some preliminary thoughts and research questions
Deutsch-Jozsa algorithm as a test of quantum computation
A redundancy in the existing Deutsch-Jozsa quantum algorithm is removed and a
refined algorithm, which reduces the size of the register and simplifies the
function evaluation, is proposed. The refined version allows a simpler analysis
of the use of entanglement between the qubits in the algorithm and provides
criteria for deciding when the Deutsch-Jozsa algorithm constitutes a meaningful
test of quantum computation.Comment: 10 pages, 2 figures, RevTex, Approved for publication in Phys Rev
Simple and Effective Type Check Removal through Lazy Basic Block Versioning
Dynamically typed programming languages such as JavaScript and Python defer
type checking to run time. In order to maximize performance, dynamic language
VM implementations must attempt to eliminate redundant dynamic type checks.
However, type inference analyses are often costly and involve tradeoffs between
compilation time and resulting precision. This has lead to the creation of
increasingly complex multi-tiered VM architectures.
This paper introduces lazy basic block versioning, a simple JIT compilation
technique which effectively removes redundant type checks from critical code
paths. This novel approach lazily generates type-specialized versions of basic
blocks on-the-fly while propagating context-dependent type information. This
does not require the use of costly program analyses, is not restricted by the
precision limitations of traditional type analyses and avoids the
implementation complexity of speculative optimization techniques.
We have implemented intraprocedural lazy basic block versioning in a
JavaScript JIT compiler. This approach is compared with a classical flow-based
type analysis. Lazy basic block versioning performs as well or better on all
benchmarks. On average, 71% of type tests are eliminated, yielding speedups of
up to 50%. We also show that our implementation generates more efficient
machine code than TraceMonkey, a tracing JIT compiler for JavaScript, on
several benchmarks. The combination of implementation simplicity, low
algorithmic complexity and good run time performance makes basic block
versioning attractive for baseline JIT compilers
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