Reports de recerca
http://hdl.handle.net/2117/3094
Fri, 09 Oct 2015 12:30:50 GMT2015-10-09T12:30:50ZAdaptive clock with useful jitter
http://hdl.handle.net/2117/27967
Adaptive clock with useful jitter
Cortadella Fortuny, Jordi; Lavagno, Luciano; López Muñoz, Pedro; Lupon Navazo, Marc; Moreno Vega, Alberto; Roca Pérez, Antoni; Sapatnekar, Sachin S.
The growing variability in nanoelectronic devices due to uncertainties from the manufacturing process and environmental conditions (power supply, temperature, aging) requires increasing design guardbands, forcing circuits to work with conservative clock frequencies. Various schemes for clock generation based on ring oscillators have been proposed with the goal to mitigate the power and performance losses
attributable to variability. However, there has been no systematic analysis to quantify the benefits of such schemes.This paper presents and analyzes an Adaptive Clocking scheme with
Useful Jitter (ACUJ) that uses variability as an opportunity to reduce power by adapting the clock frequency to the varying environmental conditions and, thus, reducing guardband margins significantly. Power can be reduced between 20% and 40% at iso-performance and performance can be boosted by similar amounts at iso-power. Additionally, energy savings can be translated to substantial advantages in terms of reliability and thermal management. More importantly, the technology can be adopted with minimal modifications to conventional EDA flows.
Report - Departament Ciències de la Computació
Tue, 19 May 2015 00:00:00 GMThttp://hdl.handle.net/2117/279672015-05-19T00:00:00ZOn the complexity of exchanging
http://hdl.handle.net/2117/27400
On the complexity of exchanging
Molinero Albareda, Xavier; Olsen, Martin; Serna Iglesias, María José
We analyze the computational complexity of the problem of deciding
whether, for a given simple game, there exists the possibility of rearranging the participants in a set of j given losing coalitions into a set of j winning coalitions. We also look at the problem of turning winning coalitions into losing coalitions. We analyze the problem when the simple game is represented by a list of wining, losing, minimal winning or maximal loosing coalitions.
Tue, 24 Mar 2015 00:00:00 GMThttp://hdl.handle.net/2117/274002015-03-24T00:00:00ZEvent-based real-time decomposed conformance analysis
http://hdl.handle.net/2117/22872
Event-based real-time decomposed conformance analysis
vanden Broucke, Seppe; Muñoz Gama, Jorge; Carmona Vargas, Josep; Baesens, Bart; Vanthienen, Jan
Process mining deals with the extraction of knowledge from event logs. One important task within this research field is denoted as conformance checking, which aims to diagnose deviations and discrepancies between modeled behavior and real-life, observed behavior. Conformance checking techniques still face some challenges, among which scalability, timeliness and traceability issues. In this paper, we propose a novel conformance analysis methodology to support the real-time monitoring of event-based data streams, which is shown to be more efficient than related approaches and able to localize deviations in a more fine-grained manner. Our developed approach can be directly applied in business process contexts where rapid reaction times are crucial; an exhaustive case example is provided to evidence the validity of the approach.
Fri, 13 Dec 2013 00:00:00 GMThttp://hdl.handle.net/2117/228722013-12-13T00:00:00ZOn the proper intervalization of colored caterpillar trees
http://hdl.handle.net/2117/12953
On the proper intervalization of colored caterpillar trees
Álvarez Faura, M. del Carme; Serna Iglesias, María José
This paper studies the computational complexity of the Proper interval colored graph problem (picg), when the input graph is a colored caterpillar, parameterized by hair length. In order prove our result we establish a close relationship between the picg and a graph layout problem the Proper colored layout problem (pclp). We show a dichotomy: the picg and the pclp are NP-complete for colored caterpillars of hair length ≥ 2, while both problems are in P for colored caterpillars of hair length < 2. For the hardness results we provide a reduction from the Multiprocessor Scheduling problem, while the polynomial time results follow from a characterization in terms of forbidden subgraphs.
Sun, 01 Nov 2009 00:00:00 GMThttp://hdl.handle.net/2117/129532009-11-01T00:00:00ZSensor field: a computational model
http://hdl.handle.net/2117/12934
Sensor field: a computational model
Álvarez Faura, M. del Carme; Duch Brown, Amalia; Gabarró Vallès, Joaquim; Serna Iglesias, María José
We introduce a formal model of computation for networks of tiny artifacts, the static synchronous sensor field model (SSSF) which
considers that the devices communicate through a fixed communication graph and interact with the environment through input/output data streams. We analyze the performance of SSSFs solving two sensing problems the Average Monitoring and the Alerting problems. For constant memory SSSFs we show that the set of recognized languages is contained in DSPACE(n+m) where n is the number of nodes of the communication graph and m its number of edges. Finally we explore the capabilities of SSSFs having sensing and additional non-sensing constant memory devices.
Wed, 23 Sep 2009 00:00:00 GMThttp://hdl.handle.net/2117/129342009-09-23T00:00:00ZTheoretical aspects of graph models for MANETS
http://hdl.handle.net/2117/9758
Theoretical aspects of graph models for MANETS
Díaz Cort, Josep; Dieter Wilhelm, Mitsche; Santi, Paolo
We survey the main theoretical aspects of models for Mobile Ad
Hoc Networks (MANETs). We present theoretical characterizations of mobile
network structural properties, di erent dynamic graph models of MANETs,
and nally we give detailed summaries of a few selected articles. In particular,
we focus on articles dealing with connectivity of mobile networks, and on articles
which show that mobility can be used to propagate information between
nodes of the network while at the same time maintaining small transmission
distances, and thus saving energy.
Mon, 01 Mar 2010 00:00:00 GMThttp://hdl.handle.net/2117/97582010-03-01T00:00:00ZMaximum tolerance and maximum greatest tolerance
http://hdl.handle.net/2117/9550
Maximum tolerance and maximum greatest tolerance
Freixas Bosch, Josep; Molinero Albareda, Xavier
An important consideration when applying neural networks is the sensitivity
to weights and threshold in strict separating systems representing a
linearly separable function. Two parameters have been introduced to measure
the relative errors in weights and threshold of strict separating systems:
the tolerance and the greatest tolerance. Given an arbitrary separating system
we study which is the equivalent separating system that provides maximum
tolerance or/and maximum greatest tolerance.
Wed, 23 Sep 2009 00:00:00 GMThttp://hdl.handle.net/2117/95502009-09-23T00:00:00ZWeighted games without a unique minimal representation in integers
http://hdl.handle.net/2117/9295
Weighted games without a unique minimal representation in integers
Freixas Bosch, Josep; Molinero Albareda, Xavier
Recerca de jocs amb mínim número de jugadors sense representacions enteres mínimes o mínimes normalitzades
Isbell in 1959 was the first to find a weighted game without a minimum integer realization
in which the affected players do not play a symmetric role in the game. His example has 12
players is a weighted decisive game, i.e. a weighted game for which a coalition wins iff its
complement loses. The goal of this paper is to provide a procedure for weighted games that
allows finding out what is the minimum number of players needed to get a weighted game
without a minimum integer weighted representation in which the affected players do not play
a symmetric role in the game. We prove, by means of an algorithm, that the minimum number
of voters required is 9.
Thu, 01 Jan 2009 00:00:00 GMThttp://hdl.handle.net/2117/92952009-01-01T00:00:00ZOn the complexity of problems on simple games
http://hdl.handle.net/2117/8956
On the complexity of problems on simple games
Freixas Bosch, Josep; Molinero Albareda, Xavier; Olsen, Martin; Serna Iglesias, María José
Simple games cover voting systems in which a single alternative, such
as a bill or an amendment, is pitted against the status quo. A simple game
or a yes–no voting system is a set of rules that specifies exactly which
collections of “yea” votes yield passage of the issue at hand, each of these
collections of “yea” voters forms a winning coalition. We are interested in
performing a complexity analysis on problems defined on such families of
games. This analysis as usual depends on the game representation used as
input. We consider four natural explicit representations: winning, losing,
minimal winning, and maximal losing. We first analyze the complexity of
testing whether a game is simple and testing whether a game is weighted.
We show that, for the four types of representations, both problems can be
solved in polynomial time. Finally, we provide results on the complexity
of testing whether a simple game or a weighted game is of a special type.
We analyze strongness, properness, decisiveness and homogeneity, which
are desirable properties to be fulfilled for a simple game. We finalize
with some considerations on the possibility of representing a game in a
more succinct representation showing a natural representation in which
the recognition problem is hard.
Thu, 08 Oct 2009 00:00:00 GMThttp://hdl.handle.net/2117/89562009-10-08T00:00:00ZA Fibonacci sequence for linear structures with two types of components
http://hdl.handle.net/2117/7703
A Fibonacci sequence for linear structures with two types of components
Freixas Bosch, Josep; Molinero Albareda, Xavier; Roura Ferret, Salvador
We investigate binary voting systems with two types of voters and a hierarchy among
the members in each type, so that members in one class have more influence or importance
than members in the other class. The purpose of this paper is to count, up to isomorphism,
the number of these voting systems for an arbitrary number of voters. We obtain a closed formula for the number of these systems, this formula follows a Fibonacci sequence with a smooth polynomial variation on the number of voters.
Thu, 23 Jul 2009 00:00:00 GMThttp://hdl.handle.net/2117/77032009-07-23T00:00:00Z