3,313 research outputs found
The alldifferent Constraint: A Survey
The constraint of difference is known to the constraint programming community
since Lauriere introduced Alice in 1978. Since then, several solving strategies
have been designed for this constraint. In this paper we give both a practical
overview and an abstract comparison of these different strategies.Comment: 12 pages, 3 figures, paper accepted at the 6th Annual workshop of the
ERCIM Working Group on Constraint
An object-oriented approach to application generation
The TUBA system consists of a set of integrated tools for the generation of business-oriented applications. Tools and applications have a modular structure, represented by class objects. The article describes the architecture of the environments for file processing, screen handling and report writing
Generation of file processing programs based on JSP
This paper describes the generation of file processing programmes within the TUBA environment. Program structures are derived from data structures according to the JSP method. Expressions describing output data are specified in user-system dialogues. The program specifications are stored in the dictionary. Complete executable programs can be generated from these specifications
Postponing Branching Decisions
Solution techniques for Constraint Satisfaction and Optimisation Problems
often make use of backtrack search methods, exploiting variable and value
ordering heuristics. In this paper, we propose and analyse a very simple method
to apply in case the value ordering heuristic produces ties: postponing the
branching decision. To this end, we group together values in a tie, branch on
this sub-domain, and defer the decision among them to lower levels of the
search tree. We show theoretically and experimentally that this simple
modification can dramatically improve the efficiency of the search strategy.
Although in practise similar methods may have been applied already, to our
knowledge, no empirical or theoretical study has been proposed in the
literature to identify when and to what extent this strategy should be used.Comment: 11 pages, 3 figure
Decomposition Based Search - A theoretical and experimental evaluation
In this paper we present and evaluate a search strategy called Decomposition
Based Search (DBS) which is based on two steps: subproblem generation and
subproblem solution. The generation of subproblems is done through value
ranking and domain splitting. Subdomains are explored so as to generate,
according to the heuristic chosen, promising subproblems first.
We show that two well known search strategies, Limited Discrepancy Search
(LDS) and Iterative Broadening (IB), can be seen as special cases of DBS. First
we present a tuning of DBS that visits the same search nodes as IB, but avoids
restarts. Then we compare both theoretically and computationally DBS and LDS
using the same heuristic. We prove that DBS has a higher probability of being
successful than LDS on a comparable number of nodes, under realistic
assumptions. Experiments on a constraint satisfaction problem and an
optimization problem show that DBS is indeed very effective if compared to LDS.Comment: 16 pages, 8 figures. LIA Technical Report LIA00203, University of
Bologna, 200
On Global Warming (Softening Global Constraints)
We describe soft versions of the global cardinality constraint and the
regular constraint, with efficient filtering algorithms maintaining domain
consistency. For both constraints, the softening is achieved by augmenting the
underlying graph. The softened constraints can be used to extend the
meta-constraint framework for over-constrained problems proposed by Petit,
Regin and Bessiere.Comment: 15 pages, 7 figures. Accepted at the 6th International Workshop on
Preferences and Soft Constraint
Microbubble formation and pinch-off scaling exponent in flow-focusing devices
We investigate the gas jet breakup and the resulting microbubble formation in
a microfluidic flow-focusing device using ultra high-speed imaging at 1 million
frames/s. In recent experiments [Dollet et al., Phys. Rev. Lett. 100, 034504
(2008)] it was found that in the final stage of the collapse the radius of the
neck scales with time with a 1/3 power-law exponent, which suggested that gas
inertia and the Bernoulli suction effect become important. Here, ultra
high-speed imaging was used to capture the complete bubble contour and quantify
the gas flow through the neck. It revealed that the resulting decrease in
pressure, due to Bernoulli suction, is too low to account for an accelerated
pinch-off. The high temporal resolution images enable us to approach the final
moment of pinch-off to within 1 {\mu}s. We observe that the final moment of
bubble pinch-off is characterized by a scaling exponent of 0.41 +/- 0.01. This
exponent is approximately 2/5, which can be derived, based on the observation
that during the collapse the neck becomes less slender, due to the exclusive
driving through liquid inertia
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