A spill code minimization algorithm for loops

Loops are the main source of parallelism in applications. The issue of finding an optimal register allocation to loops has been an open issue for some time. In this case optimal refers to the minimization of spills from registers to memory. In this paper we address this issue and present an optimal, but exponential algorithm which allocates registers to loop bodies such that the spill code is minimal. We also show heuristic modifications to the algorithm which perform in practice as well as the exponential approach. Finally, we examine this algorithm's feasibility in production compilers

Percolation scheduling for non-VLIW machines

Percolation Scheduling, a technique for compile-time code parallelization, has proven very successful for exploiting fine-grain irregular parallelism in ordinary programs. Currently, this technology is targeted only to VLIW (Very Long Instruction Word) machines, which have the advantages of 'free' synchronization and communication. Shared memory multi-processors can simulate the execution characteristics of VLIW machines with the use of static barriers. Preliminary results show that Percolation Scheduling can be used with good results on this type of architecture by increasing the granularity from operation level to source statement level, removing any redundant synchronization, and providing an efficient implementation of multi-way jumps

Applying an abstract data structure description approach to parallelizing scientific pointer programs

Even though impressive progress has been made in the area of parallelizing scientific programs with arrays, the application of similar techniques to programs with pointer data structures has remained difficult. Unlike arrays which have a small number of well-defined properties that can be utilized by a parallelizing compiler, pointer data structures are used to implement a wide variety of structures that exhibit a much more diverse set of properties. The complexity and diversity of such properties means that, in general, scientific programs with pointer data structures cannot be effectively analyzed by an optimizing and parallelizing compiler.In order to provide a system in which the compiler can fully utilize the properties of different types of pointer data structures, we have developed a mechanism for the Abstract Description of Data Structures (ADDS). With our approach, the programmer can explicitly describe important properties such as dimensionality of the pointer data structure, independence of dimensions, and direction of traversal. These abstract descriptions of pointer data structures are then used by the compiler to guide analysis, optimization, and parallelization.In this paper we summarize the ADDS approach through the use of numerous examples of data structures used in scientific computations, we illustrate how such declarations are natural and non-tedious to specify, and we show how the ADDS declarations can be used to improve compile-time analysis. In order to demonstrate the viability of our approach, we show how such techniques can be used to parallelize an important class of scientific codes which naturally use recursive pointer data structures. In particular, we use our approach to develop the parallelization of an N-body simulation that is based on a relatively complicated pointer data structure, and we report the speedup results for a Sequent multiprocessor

STOCHASTIC CHOICE ANALYSIS OF TOURISM DESTINATIONS

The analysis of tourist destination choice, defined by intra-country administrative units and by product types "coastal/inland and village/city", permits the characterisation of tourist flow behaviour, which is fundamental for public planning and business management. In this study, we analyse the determinant factors of tourist destination choice, proposing various research hypotheses relative to the impact of destination attributes and the personal characteristics of tourists. The methodology applied estimates Nested and Random Coefficients Multinomial Logit Models, which allow control over possible correlations among different destinations. The empirical application is realised in Spain on a sample of 3,781 individuals and allows us to conclude that prices, distance to the destination and personal motivations are determinants in destination choice.Tourism Marketing, Intra-country destination, Coastal/inland, Village/city, Nested and Random Coefficients Logit Models.

ANALYSING THREE BASIC DECISIONS OF TOURISTS: GOING AWAY, GOING ABROAD AND GOING ON TOUR

This study analyses determinant factors in the taking of three basic decisions on the part of holidaymakers: going on holiday, foreign holidays and multi-destination holidays. We propose various research hypotheses relating to the impact on these decisions of various personal characteristics. The methodology used estimates various Binomial Logit models. The empirical application carried out in Spain on a sample of 3,781 individuals allows us to conclude that personal characteristics related to the chosen destination, personal restrictions and socio-demographic and psychographic characteristics are determinants of these decisions. This study analyses determinant factors in the taking of three basic decisions onthe part of holidaymakers: going on holiday, foreign holidays and multi-destinationholidays. We propose various research hypotheses relating to the impact on thesedecisions of various personal characteristics. The methodology used estimates variousBinomial Logit models. The empirical application carried out in Spain on a sample of3,781 individuals allows us to conclude that personal characteristics related to thechosen destination, personal restrictions and socio-demographic and psychographiccharacteristics are determinants of these decisions.Tourism Marketing, Choice Behaviour, Probabilistic Choice Models Marketing Turístico, Comportamiento de Elección, Modelos Probabilísticos de Elección.

Oscillation of generalized differences of H\"older and Zygmund functions

In this paper we analyze the oscillation of functions having derivatives in the H\"older or Zygmund class in terms of generalized differences and prove that its growth is governed by a version of the classical Kolmogorov's Law of the Iterated Logarithm. A better behavior is obtained for functions in the Lipschitz class via an interesting connection with Calder\'on-Zygmund operators.Comment: 16 page

Fine-grain loop scheduling for MIMD machines

Previous algorithms for parallelizing loops on MIMD machines have been based on assigning one or more loop iterations to each processor, introducing synchronization as required. These methods exploit only iteration level parallelism, and ignore the parallelism that may exist at a lower level.In order to exploit parallelism both within and across iterations, our algorithm analyzes and schedules the loop at the statement level. The loop schedule reflects the expected communication and synchronization costs of the target machine. We provide test results that show that this algorithm can produce good speedup of loops on an MIMD machine

HECKIT MODELLING OF THE TWO-STAGE TOURIST CHOICE PROCESS: GOING ON HOLIDAY AND TOURISM EXPENDITURES

The objective of this paper is to decompose the process of tourist choice into two stages: taking a holiday and tourism expenditures, using the Heckit model, which avoids the problems of the methodologies applied to date. We propose hypotheses on the effect on the above decisions of tourist characteristics relating to the destination, personal restrictions and socio-demographic and psychographic characteristics. The empirical application, which is carried out in Spain on a sample of 3,781 individuals, finds a two-stage tourist choice process as the expenditure decision is correlated with that of taking a holiday. In addition, these decisions are also explained by individual tourist characteristics. El objetivo de esta investigación consiste descomponer el proceso de elecciónturístico en dos etapas, salir de vacaciones y gasto turístico, utilizando la modelizaciónHeckit que evita los problemas de las metodologías aplicadas hasta la fecha. Para ello,se proponen hipótesis de investigación acerca del efecto en las decisiones anteriores delas características de los turistas relacionadas con el destino, las restriccionespersonales, las características socio-demográficas y psicográficas. La aplicaciónempírica, efectuada en España sobre una muestra de 3.781 individuos, evidencia unproceso de elección turística bietápico ya que la decisión de gasto está correlacionadacon la de salir de vacaciones. Además, estas decisiones vienen explicadas por lascaracterísticas individuales del turista.Proceso de elección turística bietápica, salir de vacaciones, gastos en turismo, modelo Heckit. Two-stage tourist choice process, going on holiday, tourism expenditures, Heckit model.