Récursion terminale

Résumé

En informatique, la récursion terminale, aussi appelée, récursion finale, est un cas particulier de récursivité assimilée à une itération. Principe Une fonction à récursivité terminale est une fonction où l'appel récursif est la dernière instruction à être évaluée. Cette instruction est alors nécessairement « pure », c'est-à-dire qu'elle consiste en un simple appel à la fonction, et jamais à un calcul ou une composition. Par exemple, dans un langage de programmation fictif : fonction récursionTerminale(n) : // ... renvoie récursionTerminale(n - 1) fonction récursionNonTerminale(n) : // ... renvoie n + récursionNonTerminale(n - 1) récursionNonTerminale() n'est pas une récursion terminale car sa dernière instruction est une composition faisant intervenir l'appel récursif. Dans le premier cas, aucune référence aux résultats précédents n'est à conserver en mémoire, tandis que dans le second cas, tous les résultats intermédiaires doivent l'être. Les algorithme

Source officielle

https://fr.wikipedia.org/wiki/R%C3%A9cursion_terminale

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A problem that often has to be solved by compilers for functional languages targeting the Java Virtual Machine is the elimination of tail calls. This paper explains how we solved it in our Funnel compiler and presents some experimental results about the impact our technique has on both performance and size of the compiled programs.

2001

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Caching All Plans with Just One Optimizer Call

Anastasia Ailamaki, Ioannis Alagiannis, Debabrata Dash, Cristina Ileana Maier

Modern database management systems (DBMS) answer a multitude of complex queries on increasingly larger datasets. Given the complexities of the queries and the numerous design features, manual design is no longer an option. Instead, automatically designing the database is vital to maximize its performance and to reduce the total cost of ownership. For this purpose, commercial DBMS feature automated physical designers suggesting an efficient DB design by using the optimizer as a cost model. Unfortunately, consulting the optimizer is timeconsuming, an effect which is typically counter-acted by drastically pruning the search space, thereby potentially missing the optimal solution. Recently techniques cache the optimizer’s output and evaluate some plans with the cached results, reducing the number of calls to the optimizer. Still, however, the cost of invoking the optimizer to fill the cache is nontrivial, undermining scalability when running workloads with thousands of queries. In this paper, we use the intermediate optimization results in a dynamic programming based optimizer to reduce the cache initialization overhead. We demonstrate the accuracy and efficiency of our techniques by implementing them on the PostgreSQL open source query optimizer. For a star-schema workload, our techniques build the cost model 5 to 10 times faster than the conventional approach, while preserving accuracy.

2010

Chargement

Compact solid-state CMOS single-photon detector array for in vivo NIR fluorescence lifetime oncology measurements

Claudio Bruschini, Edoardo Charbon, Krisztian Homicsko, Harald Arjan Robert Homulle, François Eric Powolny, Riccardo Sinisi

In near infrared fluorescence-guided surgical oncology, it is challenging to distinguish healthy from cancerous tissue. One promising research avenue consists in the analysis of the exogenous fluorophores' lifetime, which are however in the (sub-)nanosecond range. We have integrated a single-photon pixel array, based on standard CMOS SPADs (single-photon avalanche diodes), in a compact, time-gated measurement system, named FluoCam. In vivo measurements were carried out with indocyanine green (ICG)-modified derivatives targeting the alpha(v)beta(3) integrin, initially on a genetically engineered mouse model of melanoma injected with ICG conjugated with tetrameric cyclic pentapeptide (ICG-E[c(RGDfK)(4)]), then on mice carrying tumour xenografts of U87-MG (a human primary glioblastoma cell line) injected with monomeric ICG c (RGDfK). Measurements on tumor, muscle and tail locations allowed us to demonstrate the feasibility of in vivo lifetime measurements with the FluoCam, to determine the characteristic lifetimes (around 500 ps) and subtle lifetime differences between bound and unbound ICG-modified fluorophores (10% level), as well as to estimate the available photon fluxes under realistic conditions. (C) 2016 Optical Society of America

Optical Soc Amer2016

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