56,491 research outputs found
Trusting Computations: a Mechanized Proof from Partial Differential Equations to Actual Program
Computer programs may go wrong due to exceptional behaviors, out-of-bound
array accesses, or simply coding errors. Thus, they cannot be blindly trusted.
Scientific computing programs make no exception in that respect, and even bring
specific accuracy issues due to their massive use of floating-point
computations. Yet, it is uncommon to guarantee their correctness. Indeed, we
had to extend existing methods and tools for proving the correct behavior of
programs to verify an existing numerical analysis program. This C program
implements the second-order centered finite difference explicit scheme for
solving the 1D wave equation. In fact, we have gone much further as we have
mechanically verified the convergence of the numerical scheme in order to get a
complete formal proof covering all aspects from partial differential equations
to actual numerical results. To the best of our knowledge, this is the first
time such a comprehensive proof is achieved.Comment: N° RR-8197 (2012). arXiv admin note: text overlap with
arXiv:1112.179
Influence tests I: ideal composite hypothesis tests, and causal semimeasures
Ratios of universal enumerable semimeasures corresponding to hypotheses are
investigated as a solution for statistical composite hypotheses testing if an
unbounded amount of computation time can be assumed.
Influence testing for discrete time series is defined using generalized
structural equations. Several ideal tests are introduced, and it is argued that
when Halting information is transmitted, in some cases, instantaneous cause and
consequence can be inferred where this is not possible classically.
The approach is contrasted with Bayesian definitions of influence, where it
is left open whether all Bayesian causal associations of universal semimeasures
are equal within a constant. Finally the approach is also contrasted with
existing engineering procedures for influence and theoretical definitions of
causation.Comment: 29 pages, 3 figures, draf
Chiral effective action of QCD: Precision tests, questions and electroweak extensions
This talk first discusses some aspects of the chiral expansion with three
light flavours related to the (non) applicability of the OZI rule. Next, the
extension of ChPT to an effective theory of the full standard model is
considered. Some applications of a systematic description of the coupling
constants by sum rules (e.g. to the determination of quark masses and
decays) are presented.Comment: 6 pages, plenary talk at the International Conference on QCD and
Hadronic physics, Beijing 16-20 June 200
Explaining Adaptation in Genetic Algorithms With Uniform Crossover: The Hyperclimbing Hypothesis
The hyperclimbing hypothesis is a hypothetical explanation for adaptation in
genetic algorithms with uniform crossover (UGAs). Hyperclimbing is an
intuitive, general-purpose, non-local search heuristic applicable to discrete
product spaces with rugged or stochastic cost functions. The strength of this
heuristic lie in its insusceptibility to local optima when the cost function is
deterministic, and its tolerance for noise when the cost function is
stochastic. Hyperclimbing works by decimating a search space, i.e. by
iteratively fixing the values of small numbers of variables. The hyperclimbing
hypothesis holds that UGAs work by implementing efficient hyperclimbing. Proof
of concept for this hypothesis comes from the use of a novel analytic technique
involving the exploitation of algorithmic symmetry. We have also obtained
experimental results that show that a simple tweak inspired by the
hyperclimbing hypothesis dramatically improves the performance of a UGA on
large, random instances of MAX-3SAT and the Sherrington Kirkpatrick Spin
Glasses problem.Comment: 22 pages, 5 figure
Computing hypergeometric functions rigorously
We present an efficient implementation of hypergeometric functions in
arbitrary-precision interval arithmetic. The functions , ,
and (or the Kummer -function) are supported for
unrestricted complex parameters and argument, and by extension, we cover
exponential and trigonometric integrals, error functions, Fresnel integrals,
incomplete gamma and beta functions, Bessel functions, Airy functions, Legendre
functions, Jacobi polynomials, complete elliptic integrals, and other special
functions. The output can be used directly for interval computations or to
generate provably correct floating-point approximations in any format.
Performance is competitive with earlier arbitrary-precision software, and
sometimes orders of magnitude faster. We also partially cover the generalized
hypergeometric function and computation of high-order parameter
derivatives.Comment: v2: corrected example in section 3.1; corrected timing data for case
E-G in section 8.5 (table 6, figure 2); adjusted paper siz
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