ALBCOM  Algorismia, Bioinformàtica, Complexitat i Mètodes Formals
http://hdl.handle.net/2117/3092
Fri, 23 Mar 2018 17:01:36 GMT
20180323T17:01:36Z

Institutions for navigational logics for graphical structures
http://hdl.handle.net/2117/115595
Institutions for navigational logics for graphical structures
Orejas Valdés, Fernando; Pino Blanco, Elvira; Navarro Gómez, Marisa; Lambers, Leen
We show that a Navigational Logic, i.e., a logic to express properties about graphs and about paths in graphs is a semiexact institution. In this way, we can use a number of operations to structure and modularize our specifications. Moreover, using the properties of our institution, we also show how to structure single formulas, which in our formalism could be quite complex.
Fri, 23 Mar 2018 07:50:09 GMT
http://hdl.handle.net/2117/115595
20180323T07:50:09Z
Orejas Valdés, Fernando
Pino Blanco, Elvira
Navarro Gómez, Marisa
Lambers, Leen
We show that a Navigational Logic, i.e., a logic to express properties about graphs and about paths in graphs is a semiexact institution. In this way, we can use a number of operations to structure and modularize our specifications. Moreover, using the properties of our institution, we also show how to structure single formulas, which in our formalism could be quite complex.

Underthecell routing to improve manufacturability
http://hdl.handle.net/2117/115584
Underthecell routing to improve manufacturability
Vidal Obiols, Alexandre; Cortadella Fortuny, Jordi; Petit Silvestre, Jordi
The progressive miniaturization of technology and the unequal scalability of the BEOL and FEOL layers aggravate the routing congestion problem and have a negative impact on manufacturability. Standard cells are designed in a way that they can be treated as black boxes during physical design. However, this abstraction often prevents an efficient use of its internal free resources.
This paper proposes an effective approach for using internal routing resources without sacrificing modularity. By using cell generation tools for regular layouts, libraries are enriched with cell instances that have lateral pins and allow underthecell connections between adjacent cells, thus reducing pin count, via count and routing congestion.
An approach to generate cells with regular layouts and lateral pins is proposed. Additionally, algorithms to maximize the impact of underthecell routing are presented. The proposed techniques are integrated in an industrial design flow. Experimental results show a significant reduction of design rule check violations with negligible impact on timing.
Thu, 22 Mar 2018 14:26:47 GMT
http://hdl.handle.net/2117/115584
20180322T14:26:47Z
Vidal Obiols, Alexandre
Cortadella Fortuny, Jordi
Petit Silvestre, Jordi
The progressive miniaturization of technology and the unequal scalability of the BEOL and FEOL layers aggravate the routing congestion problem and have a negative impact on manufacturability. Standard cells are designed in a way that they can be treated as black boxes during physical design. However, this abstraction often prevents an efficient use of its internal free resources.
This paper proposes an effective approach for using internal routing resources without sacrificing modularity. By using cell generation tools for regular layouts, libraries are enriched with cell instances that have lateral pins and allow underthecell connections between adjacent cells, thus reducing pin count, via count and routing congestion.
An approach to generate cells with regular layouts and lateral pins is proposed. Additionally, algorithms to maximize the impact of underthecell routing are presented. The proposed techniques are integrated in an industrial design flow. Experimental results show a significant reduction of design rule check violations with negligible impact on timing.

An agentbased model of the emergence and evolution of a language system for boolean coordination
http://hdl.handle.net/2117/115433
An agentbased model of the emergence and evolution of a language system for boolean coordination
Sierra Santibáñez, Josefina
This paper presents an agentbased model of the emergence and evolution of a language system for Boolean coordination. The model assumes the agents have cognitive capacities for invention, adoption, abstraction, repair and adaptation, a common lexicon for basic concepts, and the ability to construct complex concepts using recursive combinations of basic concepts and logical operations such as negation, conjunction or disjunction. It also supposes the agents initially have neither a lexicon for logical operations nor the ability to express logical combinations of basic concepts through language. The results of the experiments we have performed show that a language system for Boolean coordination emerges as a result of a process of selforganisation of the agents' linguistic interactions when these agents adapt their preferences for vocabulary, syntactic categories and word order to those they observe are used more often by other agents.
Such a language system allows the unambiguous communication of higherorder logic terms representing logical combinations of basic properties with nontrivial recursive structure, and it can be reliably transmitted across generations according to the results of our experiments.
Furthermore, the conceptual and linguistic systems, and simplification and repair operations of the agentbased model proposed are more general than those defined in previous works, because they not only allow the simulation of the emergence and evolution of a language system for the Boolean coordination of basic properties, but also for the Boolean coordination of higherorder logic terms of any Boolean type which can represent the meaning of nouns, sentences, verbs, adjectives, adverbs, prepositions, prepositional phrases and subexpressions not traditionally analysed as forming constituents, using linguistic devices such as syntactic categories, word order and function words.
Tue, 20 Mar 2018 08:32:10 GMT
http://hdl.handle.net/2117/115433
20180320T08:32:10Z
Sierra Santibáñez, Josefina
This paper presents an agentbased model of the emergence and evolution of a language system for Boolean coordination. The model assumes the agents have cognitive capacities for invention, adoption, abstraction, repair and adaptation, a common lexicon for basic concepts, and the ability to construct complex concepts using recursive combinations of basic concepts and logical operations such as negation, conjunction or disjunction. It also supposes the agents initially have neither a lexicon for logical operations nor the ability to express logical combinations of basic concepts through language. The results of the experiments we have performed show that a language system for Boolean coordination emerges as a result of a process of selforganisation of the agents' linguistic interactions when these agents adapt their preferences for vocabulary, syntactic categories and word order to those they observe are used more often by other agents.
Such a language system allows the unambiguous communication of higherorder logic terms representing logical combinations of basic properties with nontrivial recursive structure, and it can be reliably transmitted across generations according to the results of our experiments.
Furthermore, the conceptual and linguistic systems, and simplification and repair operations of the agentbased model proposed are more general than those defined in previous works, because they not only allow the simulation of the emergence and evolution of a language system for the Boolean coordination of basic properties, but also for the Boolean coordination of higherorder logic terms of any Boolean type which can represent the meaning of nouns, sentences, verbs, adjectives, adverbs, prepositions, prepositional phrases and subexpressions not traditionally analysed as forming constituents, using linguistic devices such as syntactic categories, word order and function words.

Synthesis of alldigital delay lines
http://hdl.handle.net/2117/115402
Synthesis of alldigital delay lines
Moreno Vega, Alberto; Cortadella Fortuny, Jordi
The synthesis of delay lines (DLs) is a core task during the generation of matched delays, ring oscillator clocks or delay monitors. The main figure of merit of a DL is the fidelity to track variability. Unfortunately, complex systems have a great diversity of timing paths that exhibit different sensitivities to static and dynamic variations. Designing DLs that capture this diversity is an ardous task. This paper proposes an algorithmic approach for the synthesis of DLs that can be integrated in a conventional design flow. The algorithm uses heuristics to perform a combinatorial search in a vast space of solutions that combine different types of gates and wire lengths. The synthesized DLs are (1) all digital, i.e., built of conventional standard cells, (2) accurate in tracking variability and (3) configurable at runtime. Experimental results with a commercial standard cell library confirm the quality of the DLs that only exhibit delay mismatches of about 1% on average over all PVT corners.
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Mon, 19 Mar 2018 12:51:27 GMT
http://hdl.handle.net/2117/115402
20180319T12:51:27Z
Moreno Vega, Alberto
Cortadella Fortuny, Jordi
The synthesis of delay lines (DLs) is a core task during the generation of matched delays, ring oscillator clocks or delay monitors. The main figure of merit of a DL is the fidelity to track variability. Unfortunately, complex systems have a great diversity of timing paths that exhibit different sensitivities to static and dynamic variations. Designing DLs that capture this diversity is an ardous task. This paper proposes an algorithmic approach for the synthesis of DLs that can be integrated in a conventional design flow. The algorithm uses heuristics to perform a combinatorial search in a vast space of solutions that combine different types of gates and wire lengths. The synthesized DLs are (1) all digital, i.e., built of conventional standard cells, (2) accurate in tracking variability and (3) configurable at runtime. Experimental results with a commercial standard cell library confirm the quality of the DLs that only exhibit delay mismatches of about 1% on average over all PVT corners.

The parallel approximability of a subclass of quadratic programming
http://hdl.handle.net/2117/115216
The parallel approximability of a subclass of quadratic programming
Serna Iglesias, María José; Xhafa Xhafa, Fatos
In this paper we deal with the parallel approximability of a special class of Quadratic Programming (QP), called Smooth Positive Quadratic Programming. This subclass of QP is obtained by imposing restrictions on the coefficients of the QP instance. The Smoothness condition restricts the magnitudes of the coefficients while the positiveness requires that all the coefficients be nonnegative. Interestingly, even with these restrictions several combinatorial problems can be modeled by Smooth QP. We show NC Approximation Schemes for the instances of Smooth Positive QP. This is done by reducing the instance of QP to an instance of Positive Linear Programming, finding in NC an approximate fractional solution to the obtained program, and then rounding the fractional solution to an integer approximate solution for the original problem. Then we show how to extend the result for positive instances of bounded degree to Smooth Integer Programming problems. Finally, we formulate several important combinatorial problems as Positive Quadratic Programs (or Positive Integer Programs) in packing/covering form and show that the techniques presented can be used to obtain NC Approximation Schemes for "dense" instances of such problems.
Thu, 15 Mar 2018 13:50:18 GMT
http://hdl.handle.net/2117/115216
20180315T13:50:18Z
Serna Iglesias, María José
Xhafa Xhafa, Fatos
In this paper we deal with the parallel approximability of a special class of Quadratic Programming (QP), called Smooth Positive Quadratic Programming. This subclass of QP is obtained by imposing restrictions on the coefficients of the QP instance. The Smoothness condition restricts the magnitudes of the coefficients while the positiveness requires that all the coefficients be nonnegative. Interestingly, even with these restrictions several combinatorial problems can be modeled by Smooth QP. We show NC Approximation Schemes for the instances of Smooth Positive QP. This is done by reducing the instance of QP to an instance of Positive Linear Programming, finding in NC an approximate fractional solution to the obtained program, and then rounding the fractional solution to an integer approximate solution for the original problem. Then we show how to extend the result for positive instances of bounded degree to Smooth Integer Programming problems. Finally, we formulate several important combinatorial problems as Positive Quadratic Programs (or Positive Integer Programs) in packing/covering form and show that the techniques presented can be used to obtain NC Approximation Schemes for "dense" instances of such problems.

Parallel skeletons for Tabu search method
http://hdl.handle.net/2117/115214
Parallel skeletons for Tabu search method
Blesa Aguilera, Maria Josep; Hernàndez, Lluis; Xhafa Xhafa, Fatos
We present two generic parallel skeletons for the tabu search methoda well known metaheuristic for approximately solving combinatorial optimization problems. The first skeleton is based on independent runs while the second in the classical masterslave model. Our starting point is the design and implementation of a sequential skeleton that is used later as basis for the two parallel skeletons. Both skeletons provide the user with the following: a permit to obtain parallel implementations of the tabu search method for concrete combinatorial optimization problems from existing sequential implementations; there is no need for the user to know either parallel programming or communication libraries; and the parallel implementation of tabu search for a concrete problem is obtained automatically from a sequential implementation of tabu search for the problem. The skeletons, however, require from the user a sequential instantiation of the tabu search method for the problem at hand. The skeletons are implemented in C++ using MPI as the communication library and offer genericity, flexibility, component reuse, robustness and time savings. We have instantiated the two skeletons for the 01 multidimensional knapsack problem, among others, for which we report computational results.
Thu, 15 Mar 2018 13:33:27 GMT
http://hdl.handle.net/2117/115214
20180315T13:33:27Z
Blesa Aguilera, Maria Josep
Hernàndez, Lluis
Xhafa Xhafa, Fatos
We present two generic parallel skeletons for the tabu search methoda well known metaheuristic for approximately solving combinatorial optimization problems. The first skeleton is based on independent runs while the second in the classical masterslave model. Our starting point is the design and implementation of a sequential skeleton that is used later as basis for the two parallel skeletons. Both skeletons provide the user with the following: a permit to obtain parallel implementations of the tabu search method for concrete combinatorial optimization problems from existing sequential implementations; there is no need for the user to know either parallel programming or communication libraries; and the parallel implementation of tabu search for a concrete problem is obtained automatically from a sequential implementation of tabu search for the problem. The skeletons, however, require from the user a sequential instantiation of the tabu search method for the problem at hand. The skeletons are implemented in C++ using MPI as the communication library and offer genericity, flexibility, component reuse, robustness and time savings. We have instantiated the two skeletons for the 01 multidimensional knapsack problem, among others, for which we report computational results.

On the relation between graph distance and Euclidean distance in random geometric graphs
http://hdl.handle.net/2117/115054
On the relation between graph distance and Euclidean distance in random geometric graphs
Díaz Cort, Josep; Dieter Wilhelm, Mitsche; Perarnau Llobet, Guillem; Pérez Giménez, Xavier
Given any two vertices u, v of a random geometric graph G(n, r), denote by dE(u, v) their Euclidean distance and by dE(u, v) their graph distance. The problem of finding upper bounds on dG(u, v) conditional on dE(u, v) that hold asymptotically almost surely has received quite a bit of attention in the literature. In this paper we improve the known upper bounds for values of r=¿(vlogn) (that is, for r above the connectivity threshold). Our result also improves the best known estimates on the diameter of random geometric graphs. We also provide a lower bound on dE(u, v) conditional on dE(u, v).
Mon, 12 Mar 2018 09:24:10 GMT
http://hdl.handle.net/2117/115054
20180312T09:24:10Z
Díaz Cort, Josep
Dieter Wilhelm, Mitsche
Perarnau Llobet, Guillem
Pérez Giménez, Xavier
Given any two vertices u, v of a random geometric graph G(n, r), denote by dE(u, v) their Euclidean distance and by dE(u, v) their graph distance. The problem of finding upper bounds on dG(u, v) conditional on dE(u, v) that hold asymptotically almost surely has received quite a bit of attention in the literature. In this paper we improve the known upper bounds for values of r=¿(vlogn) (that is, for r above the connectivity threshold). Our result also improves the best known estimates on the diameter of random geometric graphs. We also provide a lower bound on dE(u, v) conditional on dE(u, v).

Network creation games: structure vs anarchy
http://hdl.handle.net/2117/114967
Network creation games: structure vs anarchy
Álvarez Faura, M. del Carme; Messegué Buisan, Arnau
We study Nash equilibria and the price of anarchy in the classical model of Network Creation Games introduced by Fabrikant et al. In this model every agent (node) buys links at a prefixed price a > 0 in order to get connected to the network formed by all the n agents. In this setting, the reformulated tree conjecture states that for a > n, every Nash equilibrium network is a tree. Since it was shown that the price of anarchy for trees is constant, if the tree conjecture were true, then the price of anarchy would be constant for a > n. Moreover, Demaine et al. conjectured that the price of anarchy for this model is constant.
Up to now the last conjecture has been proven in (i) the lower range, for a = O(n1o¿) with o¿ = 1 and (ii) in the upper range, for a > 65n. In
¿log n
contrast, the best upper bound known for the price of anarchy for the
remaining range is 2O(vlog n).
In this paper we give new insights into the structure of the Nash equilibria for different ranges of a and we enlarge the range for which the price of anarchy is constant. Regarding the upper range, we prove that every Nash equilibrium is a tree for a > 17n and that the price of anarchy is constant even for a > 9n. In the lower range, we show that any Nash equilibrium for a < n/C with C > 4, induces an o¿distancealmost uniform graph.
Fri, 09 Mar 2018 08:25:09 GMT
http://hdl.handle.net/2117/114967
20180309T08:25:09Z
Álvarez Faura, M. del Carme
Messegué Buisan, Arnau
We study Nash equilibria and the price of anarchy in the classical model of Network Creation Games introduced by Fabrikant et al. In this model every agent (node) buys links at a prefixed price a > 0 in order to get connected to the network formed by all the n agents. In this setting, the reformulated tree conjecture states that for a > n, every Nash equilibrium network is a tree. Since it was shown that the price of anarchy for trees is constant, if the tree conjecture were true, then the price of anarchy would be constant for a > n. Moreover, Demaine et al. conjectured that the price of anarchy for this model is constant.
Up to now the last conjecture has been proven in (i) the lower range, for a = O(n1o¿) with o¿ = 1 and (ii) in the upper range, for a > 65n. In
¿log n
contrast, the best upper bound known for the price of anarchy for the
remaining range is 2O(vlog n).
In this paper we give new insights into the structure of the Nash equilibria for different ranges of a and we enlarge the range for which the price of anarchy is constant. Regarding the upper range, we prove that every Nash equilibrium is a tree for a > 17n and that the price of anarchy is constant even for a > 9n. In the lower range, we show that any Nash equilibrium for a < n/C with C > 4, induces an o¿distancealmost uniform graph.

Increasing the robustness of digital circuits with ring oscillator clocks
http://hdl.handle.net/2117/114922
Increasing the robustness of digital circuits with ring oscillator clocks
Machado, Lucas; Roca Pérez, Antoni; Cortadella Fortuny, Jordi
Technology scaling enables lower supply voltages, but also increases power density of integrated circuits. In this context, power integrity becomes a major concern in the implementation of highperformance designs. This paper analyzes the influence of Ring Oscillator Clocks (ROCs) on mitigating the impacts of voltage noise. A design with an ROC as the clock source is able to work correctly even in the presence of severe and unpredictable voltage emergencies, without degrading the average performance and power metrics of the circuit. ROCs offer an instantaneous and continuous adaptation to the environment conditions, thus reducing the margins used to prevent timing failures. ROCs provide robustness independently of the power delivery network, thus relaxing
the constraints required for the design of the PCB and package. As a byproduct, the inherent jitter generated by ROCs produces a spreadspectrum effect that reduces electromagnetic emissions.
Thu, 08 Mar 2018 11:16:26 GMT
http://hdl.handle.net/2117/114922
20180308T11:16:26Z
Machado, Lucas
Roca Pérez, Antoni
Cortadella Fortuny, Jordi
Technology scaling enables lower supply voltages, but also increases power density of integrated circuits. In this context, power integrity becomes a major concern in the implementation of highperformance designs. This paper analyzes the influence of Ring Oscillator Clocks (ROCs) on mitigating the impacts of voltage noise. A design with an ROC as the clock source is able to work correctly even in the presence of severe and unpredictable voltage emergencies, without degrading the average performance and power metrics of the circuit. ROCs offer an instantaneous and continuous adaptation to the environment conditions, thus reducing the margins used to prevent timing failures. ROCs provide robustness independently of the power delivery network, thus relaxing
the constraints required for the design of the PCB and package. As a byproduct, the inherent jitter generated by ROCs produces a spreadspectrum effect that reduces electromagnetic emissions.

Waveform Transition Graphs: a designerfriendly formalism for asynchronous behaviours
http://hdl.handle.net/2117/114897
Waveform Transition Graphs: a designerfriendly formalism for asynchronous behaviours
Cortadella Fortuny, Jordi; Moreno Vega, Alberto; Sokolov, Danil; Yakovlev, Alex; Lloyd, David
The paper proposes a new formal model for describing asynchronous behaviours involving the interplay of causality, concurrency and choice. The model is called Waveform Transition Graphs. Its main aim is simplifying the learning process for industrial engineers in accessing powerful synthesis tools provided for Signal Transition Graphs by sacrificing some of the expressive power of the latter. This formalism is developed based on feedback from engineers of Dialog Semiconductor.
Wed, 07 Mar 2018 12:36:21 GMT
http://hdl.handle.net/2117/114897
20180307T12:36:21Z
Cortadella Fortuny, Jordi
Moreno Vega, Alberto
Sokolov, Danil
Yakovlev, Alex
Lloyd, David
The paper proposes a new formal model for describing asynchronous behaviours involving the interplay of causality, concurrency and choice. The model is called Waveform Transition Graphs. Its main aim is simplifying the learning process for industrial engineers in accessing powerful synthesis tools provided for Signal Transition Graphs by sacrificing some of the expressive power of the latter. This formalism is developed based on feedback from engineers of Dialog Semiconductor.