73,682 research outputs found
Experiments towards model-based testing using Plan 9: Labelled transition file systems, stacking file systems, on-the-fly coverage measuring
We report on experiments that we did on Plan 9/Inferno to gain more experience with the file-system-as-tool-interface approach. We reimplemented functionality that we earlier worked on in Unix, trying to use Plan 9 file system interfaces. The application domain for those experiments was model-based testing.\ud
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The idea we wanted to experiment with consists of building small, reusable pieces of functionality which are then composed to achieve the intended functionality. In particular we want to experiment with the idea of 'stacking' file servers (fs) on top of each other, where the upper fs acts as a 'filter' on the data and structure provided by the lower fs.\ud
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For this experiment we designed a file system interface (ltsfs) that gives fine-grained access to a labelled transition system, and made two implementations of it.\ud
We developed a small fs that, when 'stacked' on top of the ltsfs, extends it with additional files, and an application that uses the resulting file system.\ud
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The hope was that an interface like the one offered by ltsfs could be used as a general interface between (specification language specific) programs that give access to state spaces and (specification language independent) programs that use (walk) those state spaces like simulators, model checkers, or test derivation programs.\ud
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Initial results (obtained on a less-than-modern machine) suggest that, although the approach by itself is definitely feasible in principle, in practice the fine-grained access offered by ltsfs may involve many file (9p) transactions which may seriously affect performance. In Unix we used a more conservative approach where the access was less fine-grained which likely explains why there we did not suffer from this problem.\ud
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In addition we report on experiments to use acid to obtain coverage information that is updated on-the-fly while the program is running. This worked quite well. The main observation from those experiments is that the basic block notion of this approach, which has a more 'semantical' nature, differs from the more 'syntactical' nature of the basic block notion in Unix coverage measurement tools\ud
like tcov or gcov
Average site perimeter of directed animals on the two-dimensional lattices
We introduce new combinatorial (bijective) methods that enable us to compute
the average value of three parameters of directed animals of a given area,
including the site perimeter. Our results cover directed animals of any
one-line source on the square lattice and its bounded variants, and we give
counterparts for most of them in the triangular lattices. We thus prove
conjectures by Conway and Le Borgne. The techniques used are based on Viennot's
correspondence between directed animals and heaps of pieces (or elements of a
partially commutative monoid)
The infrared fixed point of Landau gauge Yang-Mills theory: A renormalization group analysis
The infrared behavior of gluon and ghost propagators in Landau gauge
Yang-Mills theory has been at the center of an intense debate over the last
decade. Different solutions of the Dyson-Schwinger equations show a different
behavior of the propagators in the infrared: in the so-called scaling solutions
both propagators follow a power law, while in the decoupling solutions the
gluon propagator shows a massive behavior. The latest lattice results favor the
decoupling solutions. In this contribution, after giving a brief overview of
the present status of analytical and semi-analytical approaches to the infrared
regime of Landau gauge Yang-Mills theory, we will show how Callan-Symanzik
renormalization group equations in an epsilon expansion reproduce both types of
solutions and single out the decoupling solutions as the infrared-stable ones
for space-time dimensions greater than two, in agreement with the lattice
calculations.Comment: 17 pages. Talk delivered at the XIII Mexican Workshop on Particles
and Fields in Leon, Guanajuato, Mexico, October 2011. Slightly extended
version of the contribution to the conference proceeding
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