SAMIE-LSQ: set-associative multiple-instruction entry load/store queue

The load/store queue (LSQ) is one of the most complex parts of contemporary processors. Its latency is critical for the processor performance and it is usually one of the processor hotspots. This paper presents a highly banked, set-associative, multiple-instruction entry LSQ (SAMIE-LSQ,) that achieves high performance with small energy requirements. The SAMIE-LSQ classifies the memory instructions (loads and stores) based on the address to be accessed, and groups those instructions accessing the same cache line in the same entry. Our approach relies on the fact that many in-flight memory instructions access the same cache lines. Each SAMIE-LSQ entry has space for several memory instructions accessing the same cache line. This arrangement has a number of advantages. First, it significantly reduces the address comparison activity needed for memory disambiguation since there are less addresses to be compared. It also reduces the activity in the data TLB, the cache tag and cache data arrays. This is achieved by caching the cache line location and address translation in the corresponding SAMIE-LSQ entry once the access of one of the instructions in an entry is performed, so instructions that share an entry can reuse the translation, avoid the tag check and get the data directly from the concrete cache way without checking the others. Besides, the delay of the proposed scheme is lower than that required by a conventional LSQ. We show that the SAMIE-LSQ saves 82% dynamic energy for the load/store queue, 42% for the LI data cache and 73% for the data TLB, with a negligible impact on performance (0.6%)Peer ReviewedPostprint (published version

Inherently workload-balanced clustered microarchitecture

The performance of clustered microarchitectures relies on steering schemes that try to find the best trade-off between workload balance and inter-cluster communication penalties. In previously proposed clustered processors, reducing communication penalties and balancing the workload are opposite targets, since improving one usually implies a detriment in the other. In this paper we propose a new clustered microarchitecture that can minimize communication penalties without compromising workload balance. The key idea is to arrange the clusters in a ring topology in such a way that results of one cluster can be forwarded to the neighbor cluster with a very short latency. In this way, minimizing communication penalties is favored when the producer of a value and its consumer are placed in adjacent clusters, which also favors workload balance. The proposed microarchitecture is shown to outperform a state-of-the-art clustered processor. For instance, for an 8-cluster configuration and just one fully pipelined unidirectional bus, 15% speedup is achieved on average for FP programs.Peer ReviewedPostprint (published version

Low-complexity distributed issue queue

As technology evolves, power density significantly increases and cooling systems become more complex and expensive. The issue logic is one of the processor hotspots and, at the same time, its latency is crucial for the processor performance. We present a low-complexity FP issue logic (MB/spl I.bar/distr) that achieves high performance with small energy requirements. The MB/spl I.bar/distr scheme is based on classifying instructions and dispatching them into a set of queues depending on their data dependences. These instructions are selected for issuing based on an estimation of when their operands will be available, so the conventional wakeup activity is not required. Additionally, the functional units are distributed across the different queues. The energy required by the proposed scheme is substantially lower than that required by a conventional issue design, even if the latter has the ability of waking-up only unready operands. MB/spl I.bar/distr scheme reduces the energy-delay product by 35% and the energy-delay product by 18% with respect to a state-of-the-art approach.Peer ReviewedPostprint (published version

A multivariate generalized independent factor GARCH model with an application to financial stock returns

We propose a new multivariate factor GARCH model, the GICA-GARCH model , where the data are assumed to be generated by a set of independent components (ICs). This model applies independent component analysis (ICA) to search the conditionally heteroskedastic latent factors. We will use two ICA approaches to estimate the ICs. The first one estimates the components maximizing their non-gaussianity, and the second one exploits the temporal structure of the data. After estimating the ICs, we fit an univariate GARCH model to the volatility of each IC. Thus, the GICA-GARCH reduces the complexity to estimate a multivariate GARCH model by transforming it into a small number of univariate volatility models. We report some simulation experiments to show the ability of ICA to discover leading factors in a multivariate vector of financial data. An empirical application to the Madrid stock market will be presented, where we compare the forecasting accuracy of the GICA-GARCH model versus the orthogonal GARCH one

Natural expansion versus translocation in a previously human-persecuted bird of prey

Many threatened species in Europe have been expanding their distributions during recent decades owing to protection measures that overcome historical human activity that has limited their distributions. Range expansion has come about via two processes, natural expansion from existing range and reintroductions to new ranges. Reintroductions may prove to be a better way to establish populations because individuals are less subject to competitive relationships lowering breeding success than individuals expanding from existing populations. Whether this is true, however, remains uncertain. We compared success of breeding pairs of an expanding and a reintroduced population of spanish imperial eagles monitored for over 15 years in the south of Spain. We found significant differences in productivity between breeding pairs of each population. Newly established territories in reintroduction areas were almost three times more productive than new territories established as individuals expanded out from an existing population. We conclude that among these eagle populations reintroduced to new areas may fare as well or better than individuals expanding out form existing populations

La inmigración de origen familiar (I): el control de flujos y el proceso de integración en algunos países europeos

La agrupación familiar constituye una importante vía de entrada de inmigración en todos los países europeos. Los debates que se plantean en torno a su integración suelen estar poco fundados en información fiable. En este documento se hace un breve repaso de lo que se sabe sobre los orígenes, desarrollo y consecuencias de los procesos de reagrupación familiar en Europa. En un documento posterior, que complementará a éste, se expondrá lo que se ha conocido más recientemente sobre este fenómeno en España, con la esperanza de que ello aporte alguna luz sobre los caminos a elegir para el futuro o, al menos, sobre los que se deberían evitar

Efectos macroeconómicos de la inmigración : impacto sobre el empleo y los salarios de los nativos

El presente artículo examina la reflexión teórica y la evidencia empírica disponible acerca de los efectos macro-económicos de la mano de obra inmigrante. En particular sus efectos sobre el empleo y los salarios de los autóctonos. Tras desentrañar las asunciones subyacentes a la hipótesis del reemplazo y de la segmentación, compara los resultados de los estudios empíricos realizados en EEUU y en Europa. A la luz de dicha evidencia concluye que la inmigración no ha provocado un aumento del desempleo, ni en EEUU ni en Europa, si bien puede haber contribuido, aunque menos que la apertura comercial, al incremento de la desigualdad salarial en EEUU desde los años ochenta.This article analyses both the literature and available evidence on the macro-economic effects of immigration. In particular, it focuses on its effects on the native employment and wages. After disentangling the assumptions underlying the substitution and segmentation hypotheses, it compares the empirical results obtained by the European and American investigations. From this evidence, it concludes that immigration has not increased the native unemployment, neither in USA nor Europe, but it might have contributed -although in a minor extent than international trade openness- to the increasing wage inequality in USA since the early eighties

A multivariate generalized independent factor GARCH model with an application to financial stock returns

We propose a new multivariate factor GARCH model, the GICA-GARCH model , where the data are assumed to be generated by a set of independent components (ICs). This model applies independent component analysis (ICA) to search the conditionally heteroskedastic latent factors. We will use two ICA approaches to estimate the ICs. The first one estimates the components maximizing their non-gaussianity, and the second one exploits the temporal structure of the data. After estimating the ICs, we fit an univariate GARCH model to the volatility of each IC. Thus, the GICA-GARCH reduces the complexity to estimate a multivariate GARCH model by transforming it into a small number of univariate volatility models. We report some simulation experiments to show the ability of ICA to discover leading factors in a multivariate vector of financial data. An empirical application to the Madrid stock market will be presented, where we compare the forecasting accuracy of the GICA-GARCH model versus the orthogonal GARCH one.ICA, Multivariate GARCH, Factor models, Forecasting volatility

The process of family reunification among original guest-workers in Germany

'In diesem Beitrag wird der Prozess der Familienzusammenführung bei den ursprünglichen Gastarbeitern in Deutschland untersucht. Im Gegensatz zur gängigen Darstellung legen meine Erkenntnisse nahe, dass die Mehrzahl der Familienzusammenführungen schon vor dem Anwerbestopp Mitte der 1970er Jahre stattfand. Unter Verwendung von Daten des Sozio-ökonomischen Panels (SOEP) stellte ich fest, dass ungefähr die Hälfte der Ehefrauen, die ihren Männern nach Deutschland folgten, im gleichen Jahr wie ihre Männer auswanderten. Tatsächlich scheint es nicht so zu sein, dass - wie gemeinhin angenommen - der Anwerbestopp einen beschleunigenden Effekt auf die Familienzusammenführung hatte. Nach den vorliegenden Ergebnissen hatte die Kindergeldreform im Jahre 1975 einen eindeutigeren und stärkeren Einfluss auf die Erklärung der Entscheidungen der ursprünglichen Gastarbeiter in Deutschland hinsichtlich der Familienzusammenführungen. Anderseits sind aber auch andere Variablen, die sich auf die makro-ökonomischen Bedingungen in den Herkunftsländern und im Aufnahmeland, die Haushaltsgröße, das Alter der Kinder sowie die Arbeitsmarktcharakteristika der Mütter beziehen, für die Erklärung der unterschiedlichen Zeiträume, die vergingen, ehe die männlichen Einwanderer ihre Familien im Ausland wieder zusammenführten, bedeutsam.' (Autorenreferat)'This article examines the process of family reunification among original guest-workers in Germany. Contrary to conventional accounts, the findings indicate that the bulk of family reunification occurred for the most part before the halt on recruitment was imposed in the mid-seventies. Using data from the German Socio-Economic Panel (GSOEP), I find that approximately half of wives who joined their husbands in Germany migrated in the same year as their husbands. In fact, it does not seem that the ban on labour recruitment had an accelerating effect on the reunification process, as it is generally assumed. According to the obtained results, the reform of the children's allowances in 1975 had a clearer and stronger impact in explaining the family migration decisions of original guest-workers in Germany. On the other hand, variables related to the macroeconomic conditions at the origin and destination countries, the size of the household, the age of the children, and the labour market characteristics of the mother are important to account for differences in the time that elapsed until male immigrants had their families reunified abroad.' (author's abstract