Reports de recerca
http://hdl.handle.net/2117/3488
Fri, 17 Nov 2017 09:58:01 GMT2017-11-17T09:58:01ZOn some "non uniform" complexity measures
http://hdl.handle.net/2117/110729
On some "non uniform" complexity measures
Balcázar Navarro, José Luis; Díaz Cort, Josep; Gabarró Vallès, Joaquim
Non-uniform complexity measures origined in Automata and Formal Languages Theory are characterized in terms of well-known uniform complexity classes. The initial index of languages is introduced by means of several computational models. It is shown to be closely related to context-free cost, boolean circuits straight line programs, and Turing machines with sparse oracles and time or space bounds.
Thu, 16 Nov 2017 09:17:25 GMThttp://hdl.handle.net/2117/1107292017-11-16T09:17:25ZBalcázar Navarro, José LuisDíaz Cort, JosepGabarró Vallès, JoaquimNon-uniform complexity measures origined in Automata and Formal Languages Theory are characterized in terms of well-known uniform complexity classes. The initial index of languages is introduced by means of several computational models. It is shown to be closely related to context-free cost, boolean circuits straight line programs, and Turing machines with sparse oracles and time or space bounds.Diameter minimization in networks for SIMD machines
http://hdl.handle.net/2117/110701
Diameter minimization in networks for SIMD machines
Beivide Palacio, Ramon; Balcázar Navarro, José Luis
We propose an algebraic constructive method which allows to find a certain kind of networks having optimal diameter. These interconnection networks have been proposed for SIMD machines. We comapare the results with other designs, pointing out the improvement achieved with this method.
Wed, 15 Nov 2017 16:07:32 GMThttp://hdl.handle.net/2117/1107012017-11-15T16:07:32ZBeivide Palacio, RamonBalcázar Navarro, José LuisWe propose an algebraic constructive method which allows to find a certain kind of networks having optimal diameter. These interconnection networks have been proposed for SIMD machines. We comapare the results with other designs, pointing out the improvement achieved with this method.Uniform characterizations of non-uniform complexity measures
http://hdl.handle.net/2117/110675
Uniform characterizations of non-uniform complexity measures
Balcázar Navarro, José Luis; Díaz Cort, Josep; Gabarró Vallès, Joaquim
The class PSPACE/ply of sets decided within polynomial space by machines with polynomial advices is characterized in several way: we give an algebraic characterization, a parallel model characterization. Finally we define a dual class and state some of its properties.
Wed, 15 Nov 2017 12:09:44 GMThttp://hdl.handle.net/2117/1106752017-11-15T12:09:44ZBalcázar Navarro, José LuisDíaz Cort, JosepGabarró Vallès, JoaquimThe class PSPACE/ply of sets decided within polynomial space by machines with polynomial advices is characterized in several way: we give an algebraic characterization, a parallel model characterization. Finally we define a dual class and state some of its properties.Deriving specifications of embeddings in recursive program design
http://hdl.handle.net/2117/110673
Deriving specifications of embeddings in recursive program design
Roselló Balanyà, Celestí; Balcázar Navarro, José Luis; Peña Marí, Ricardo
The design of recursive functions is a well-studied subject. Design methods require a specification to start with, however, when an embedding design is attempted at, it is not clear how the specification of the embedding relates to that of the initial function. We propose a method for deriving specifications of embeddings. We show how other known formal methods, such as loop derivation or program transformation, can be related to our method in a clear fashion. The use of embedding to enhance the efficiency of programs is also discussed.
Wed, 15 Nov 2017 11:55:04 GMThttp://hdl.handle.net/2117/1106732017-11-15T11:55:04ZRoselló Balanyà, CelestíBalcázar Navarro, José LuisPeña Marí, RicardoThe design of recursive functions is a well-studied subject. Design methods require a specification to start with, however, when an embedding design is attempted at, it is not clear how the specification of the embedding relates to that of the initial function. We propose a method for deriving specifications of embeddings. We show how other known formal methods, such as loop derivation or program transformation, can be related to our method in a clear fashion. The use of embedding to enhance the efficiency of programs is also discussed.Optimal distance networks of low degree for parallel computers
http://hdl.handle.net/2117/108974
Optimal distance networks of low degree for parallel computers
Beivide Palacio, Ramon; Herrada Lillo, Enrique; Balcázar Navarro, José Luis; Arruabarrena, Agustín
We introduce and study a family of interconnection schemes, the Midimew networks, based on circulant graphs of degree 4. A family of such circulants is determined and shown to be optimal with respect to two distance parameters simultaneously, namely maximum distance and average distance, among all circulants of degree 4.. These graphs are regular, point-symmetric, and maximally connected, and one such optimal graph exists for any given number of nodes. The proposed interconnection schemes consist of mesh-connected networks with wrap-around links, and are isomorphic to the optimal distance circulants previously considered. Ways to construct one such network for any number of nodes are shown, their good properties to build interconnection schemes for multicomputers are examined, and some interesting particular cases are discussed. The problem of routing is also addressed, and a basic algorithm is provided which is adequate for implementing the routing policy required to convey messages, traversing shortest paths between nodes.
Mon, 23 Oct 2017 13:37:52 GMThttp://hdl.handle.net/2117/1089742017-10-23T13:37:52ZBeivide Palacio, RamonHerrada Lillo, EnriqueBalcázar Navarro, José LuisArruabarrena, AgustínWe introduce and study a family of interconnection schemes, the Midimew networks, based on circulant graphs of degree 4. A family of such circulants is determined and shown to be optimal with respect to two distance parameters simultaneously, namely maximum distance and average distance, among all circulants of degree 4.. These graphs are regular, point-symmetric, and maximally connected, and one such optimal graph exists for any given number of nodes. The proposed interconnection schemes consist of mesh-connected networks with wrap-around links, and are isomorphic to the optimal distance circulants previously considered. Ways to construct one such network for any number of nodes are shown, their good properties to build interconnection schemes for multicomputers are examined, and some interesting particular cases are discussed. The problem of routing is also addressed, and a basic algorithm is provided which is adequate for implementing the routing policy required to convey messages, traversing shortest paths between nodes.Identifiability and transportability in dynamic causal networks
http://hdl.handle.net/2117/101979
Identifiability and transportability in dynamic causal networks
Blondel, Gilles; Arias Vicente, Marta; Gavaldà Mestre, Ricard
In this paper we propose a causal analog to the purely observational Dynamic Bayesian Networks, which we call Dynamic Causal Networks.
We provide a sound and complete algorithm for identification of Dynamic Causal Networks, namely, for computing the effect of an intervention or experiment, based on passive observations only, whenever possible. We note the existence of two types of confounder variables that affect in substantially different ways the identification
procedures, a distinction with no analog in either Dynamic Bayesian Networks or standard causal graphs. We further propose a procedure
for the transportability of causal effects in Dynamic Causal Network settings, where the result of causal experiments in a source domain may be used for the identification of causal effects in a target domain.
Mon, 06 Mar 2017 16:15:45 GMThttp://hdl.handle.net/2117/1019792017-03-06T16:15:45ZBlondel, GillesArias Vicente, MartaGavaldà Mestre, RicardIn this paper we propose a causal analog to the purely observational Dynamic Bayesian Networks, which we call Dynamic Causal Networks.
We provide a sound and complete algorithm for identification of Dynamic Causal Networks, namely, for computing the effect of an intervention or experiment, based on passive observations only, whenever possible. We note the existence of two types of confounder variables that affect in substantially different ways the identification
procedures, a distinction with no analog in either Dynamic Bayesian Networks or standard causal graphs. We further propose a procedure
for the transportability of causal effects in Dynamic Causal Network settings, where the result of causal experiments in a source domain may be used for the identification of causal effects in a target domain.Generalising discontinuity
http://hdl.handle.net/2117/100910
Generalising discontinuity
Morrill, Glyn; Merenciano Saladrigas, Josep Maria
This paper makes two generalisations of categorial calculus of discontinuity. In the first we introduce unary modalities which mediate between continuous and discontinuous strings. In the second each of the modes of adjunction of the proposal to date, concatenation, juxtaposition and interpolation, are augmented with variants. Linguistic illustration and motivation is provided, and we show how adherence to a discipline of sorting renders the generalisations tractable within a particularly efficient logic programming paradigm.
Mon, 13 Feb 2017 11:51:52 GMThttp://hdl.handle.net/2117/1009102017-02-13T11:51:52ZMorrill, GlynMerenciano Saladrigas, Josep MariaThis paper makes two generalisations of categorial calculus of discontinuity. In the first we introduce unary modalities which mediate between continuous and discontinuous strings. In the second each of the modes of adjunction of the proposal to date, concatenation, juxtaposition and interpolation, are augmented with variants. Linguistic illustration and motivation is provided, and we show how adherence to a discipline of sorting renders the generalisations tractable within a particularly efficient logic programming paradigm.An efficient closed frequent itemset miner for the MOA stream mining system
http://hdl.handle.net/2117/99416
An efficient closed frequent itemset miner for the MOA stream mining system
Quadrana, Massimo; Bifet Figuerol, Albert Carles; Gavaldà Mestre, Ricard
Mining itemsets is a central task in data mining, both in the batch and the streaming paradigms. While robust, efficient, and well-tested implementations exist for batch mining, hardly any publicly available equivalent exists for the streaming scenario. The lack of an efficient, usable tool for the task hinders its use by practitioners and makes it difficult to assess new research in the area. To alleviate this situation, we review the algorithms described in the literature, and implement and evaluate the IncMine algorithm by Cheng, Ke, and Ng (2008) for mining frequent closed itemsets from data streams. Our implementation works on top of the MOA (Massive Online Analysis) stream mining framework to ease its use and integration with other stream mining tasks. We provide a PAC-style rigorous analysis of the quality of the output of IncMine as a function of its parameters; this type of analysis is rare in pattern mining algorithms. As a by-product, the analysis shows how one of the user-provided parameters in the original description can be removed entirely while retaining the performance guarantees. Finally, we experimentally confirm both on synthetic and real data the excellent performance of the algorithm, as reported in the original paper, and its ability to handle concept drift.
Tue, 17 Jan 2017 10:16:22 GMThttp://hdl.handle.net/2117/994162017-01-17T10:16:22ZQuadrana, MassimoBifet Figuerol, Albert CarlesGavaldà Mestre, RicardMining itemsets is a central task in data mining, both in the batch and the streaming paradigms. While robust, efficient, and well-tested implementations exist for batch mining, hardly any publicly available equivalent exists for the streaming scenario. The lack of an efficient, usable tool for the task hinders its use by practitioners and makes it difficult to assess new research in the area. To alleviate this situation, we review the algorithms described in the literature, and implement and evaluate the IncMine algorithm by Cheng, Ke, and Ng (2008) for mining frequent closed itemsets from data streams. Our implementation works on top of the MOA (Massive Online Analysis) stream mining framework to ease its use and integration with other stream mining tasks. We provide a PAC-style rigorous analysis of the quality of the output of IncMine as a function of its parameters; this type of analysis is rare in pattern mining algorithms. As a by-product, the analysis shows how one of the user-provided parameters in the original description can be removed entirely while retaining the performance guarantees. Finally, we experimentally confirm both on synthetic and real data the excellent performance of the algorithm, as reported in the original paper, and its ability to handle concept drift.Modeling cloud resources using machine learning
http://hdl.handle.net/2117/99413
Modeling cloud resources using machine learning
Berral, Josep Ll.; Gavaldà Mestre, Ricard; Torres Viñals, Jordi
Cloud computing is a new Internet infrastructure paradigm where management optimization has become a challenge to be solved, as all current management systems are human-driven or ad-hoc automatic systems that must be tuned manually by experts. Management of cloud resources require accurate information about all the elements involved (host machines, resources, offered services, and clients), and some of this information can only be obtained a posteriori. Here we present the cloud and part of its architecture as a new scenario where data mining and machine learning can be applied to discover information and improve its management thanks to modeling and prediction. As a novel case of study we show in this work the modeling of basic cloud resources using machine learning, predicting resource requirements from context information like amount of load and clients, and also predicting the quality of service from resource planning, in order to feed cloud schedulers. Further, this work is an important part of our ongoing research program, where accurate models and predictors are essential to optimize cloud management autonomic systems.
Tue, 17 Jan 2017 10:07:13 GMThttp://hdl.handle.net/2117/994132017-01-17T10:07:13ZBerral, Josep Ll.Gavaldà Mestre, RicardTorres Viñals, JordiCloud computing is a new Internet infrastructure paradigm where management optimization has become a challenge to be solved, as all current management systems are human-driven or ad-hoc automatic systems that must be tuned manually by experts. Management of cloud resources require accurate information about all the elements involved (host machines, resources, offered services, and clients), and some of this information can only be obtained a posteriori. Here we present the cloud and part of its architecture as a new scenario where data mining and machine learning can be applied to discover information and improve its management thanks to modeling and prediction. As a novel case of study we show in this work the modeling of basic cloud resources using machine learning, predicting resource requirements from context information like amount of load and clients, and also predicting the quality of service from resource planning, in order to feed cloud schedulers. Further, this work is an important part of our ongoing research program, where accurate models and predictors are essential to optimize cloud management autonomic systems.The Plogi and ACi-1 operators on the polynomial time hierarchy
http://hdl.handle.net/2117/97278
The Plogi and ACi-1 operators on the polynomial time hierarchy
Castro Rabal, Jorge; Seara Ojea, Carlos
In a previous paper ([CS-92]) we studied the agreement of operators P_{log^i} and AC^{i-1} acting on NP. In this article we extend this work to other classes of the polynomial time hierarchy. We show that on Sigma_k^p, Pi_k^p, Delta_k^P and Theta_k^P-classes both operators have the same behaviour, but this coincidence does not seem to be true on other classes included in the PH hierarchy: we give a set A such that, relativized to A, P_{log^i}(P_{log^j}(NP)) is different from AC^{i-1}(P_{log^j}(NP)). As a result of these characterizations we show P_{log}(Theta_k^p) = Theta_k^p, an equality that is useful to show lowness properties. In fact, we get easily the Theta-lowness results given by Long and Sheu in their paper [LS-91]. Besides, we clarify the situation of the classes in L_2^{p,Delta} for which their membership to L_2^{p,Theta} was not clear.
Mon, 28 Nov 2016 09:01:43 GMThttp://hdl.handle.net/2117/972782016-11-28T09:01:43ZCastro Rabal, JorgeSeara Ojea, CarlosIn a previous paper ([CS-92]) we studied the agreement of operators P_{log^i} and AC^{i-1} acting on NP. In this article we extend this work to other classes of the polynomial time hierarchy. We show that on Sigma_k^p, Pi_k^p, Delta_k^P and Theta_k^P-classes both operators have the same behaviour, but this coincidence does not seem to be true on other classes included in the PH hierarchy: we give a set A such that, relativized to A, P_{log^i}(P_{log^j}(NP)) is different from AC^{i-1}(P_{log^j}(NP)). As a result of these characterizations we show P_{log}(Theta_k^p) = Theta_k^p, an equality that is useful to show lowness properties. In fact, we get easily the Theta-lowness results given by Long and Sheu in their paper [LS-91]. Besides, we clarify the situation of the classes in L_2^{p,Delta} for which their membership to L_2^{p,Theta} was not clear.