Sous-programme

Résumé

En informatique, un sous-programme est un sous-ensemble du programme dans sa hiérarchie fonctionnelle. Un sous-programme doit pouvoir mémoriser l'adresse du code appelant pour permettre, à l'aide d'une instruction spécifique, de charger le pointeur de programme avec cette adresse de retour. Cela correspond bien souvent à une routine. Cependant, la notion de sous-programme est un peu plus générale, car il ne possède pas nécessairement son propre espace de noms. C'est le cas par exemple des sous-programmes appelés par l'instruction en BASIC. Dans ce cas, la notion de variable locale n'existe donc pas. Ce terme est utilisé dans le contexte d'une conception fonctionnelle d'un logiciel, c’est-à-dire lorsque son architecture a été pensée et construite à partir des opérations qui doivent la composer. Exemple Prenons l'algorithme suivant : PROGRAMME prendre un repas DEBUT mettre_la_table () presenter (plat_du_jour) manger (plat_du_jour) presenter (dessert) manger

Source officielle

https://fr.wikipedia.org/wiki/Sous-programme

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Chargement

Complex event recognition through wearable sensors

Jean-Eudes Marie Ranvier

Complex events are instrumental in understanding advanced behaviours and properties of a system. They can represent more meaningful events as compared to simple events. In this thesis we propose to use wearable sensor signals to detect complex events. These signals are pertaining to the user's state and therefore allow us to understand advanced characteristics about her. We propose a hierarchical approach to detect simple events from the wearable sensors data and then build complex events on top of them. In order to address privacy concerns that rise from the use of sensitive signals, we propose to perform all the computation on device. While this ensures the privacy of the data, it poses the problem of having limited computational resources. This problem is tackled by introducing energy efficient approaches based on incremental algorithms. A second challenge is the multiple levels of noise in the process. A first level of noise concerns the raw signals that are inherently imprecise (e.g. inaccuracy in GPS readings). A second level of noise, that we call semantic noise, is present among the simple events detected. Some of these simple events can disturb the detection of complex events effectively acting as noise. We apply the hierarchical approach in two different contexts defining the two different parts of our thesis. In the first part, we present a mobile system that builds a representation of the user's life. This system is based on the episodic memory model, which is responsible for the storage and recollection of past experiences. Following the hierarchical approach, the system processes raw signals to detect simple events such as places where the user stayed a certain amount of time to perform an activity, therefore building sequences of detected activities. These activities are in turn processed to detect complex events that we call routines and that represent recurrent patterns in the life of the user. In the second part of this thesis, we focus on the detection of glycemic events for diabetes type-1 patients in a non-invasive manner. Diabetics are not able to properly regulate their glucose, leading to periods of high and low blood sugar. We leverage signals (Electrocardiogram (ECG), accelerometer, breathing rate) from a sport belt to infer such glycemic events. We propose a physiological model based on the variations of the ECG when the patient has low blood sugar, and an energy-based model that computes the current glucose level of the user based on her glucose intake, insulin intake and glucose consumption via physical activity. For both contexts, we evaluate our systems in term of accuracy by assessing wether the detected routines are meaningful, and wether the glycemic events are correctly detected, and in term of mobile performance, which confirms the fitness of our approaches for mobile computation.

EPFL2017

Chargement

Application of large-scale computing infrastructure for diverse environmental research applications using GC3Pie

Mathias Thierry Pierre Bavay, Michael Lehning, Sofiane Sarni

The Swiss Experiment platform (SwissEx: http://www.swiss-experiment.ch) provides a distributed storage and processing infrastructure for environmental research experiments. The aim of the second phase project (the Open Support Platform for Environmental Research, OSPER, 2012-2015) is to develop the existing infrastructure to provide scientists with an improved workflow. This improved workflow will include pre-defined, documented and connected processing routines. A large-scale computing and data facility is required to provide reliable and scalable access to data for analysis, and it is desirable that such an infrastructure should be free of traditional data handling methods. Such an infrastructure has been developed using the cloud-based part of the Swiss national infrastructure SMSCG (http://www.smscg.ch) and Academic Cloud. The infrastructure under construction supports two main usage models: 1) Ad-hoc data analysis scripts: These scripts are simple processing scripts, written by the environmental researchers themselves, which can be applied to large data sets via the high power infrastructure. Examples of this type of script are spatial statistical analysis scripts (R-based scripts), mostly computed on raw meteorological and/or soil moisture data. These provide processed output in the form of a grid, a plot, or a kml. 2) Complex models: A more intense data analysis pipeline centered (initially) around the physical process model, Alpine3D, and the MeteoIO plugin; depending on the data set, this may require a tightly coupled infrastructure. SMSCG already supports Alpine3D executions as both regular grid jobs and as virtual software appliances. A dedicated appliance with the Alpine3D specific libraries has been created and made available through the SMSCG infrastructure. The analysis pipelines are activated and supervised by simple control scripts that, depending on the data fetched from the meteorological stations, launch new instances of the Alpine3D appliance, execute locationbased subroutines at each grid point and store the results back into the central repository for post-processing. An optional extension of this infrastructure will be to provide a ’ring buffer’-type database infrastructure, such that model results (e.g. test runs made to check parameter dependency or for development) can be visualised and downloaded after completion without submitting them to a permanent storage infrastructure. Data organization Data collected from sensors are archived and classified in distributed sites connected with an open-source software middleware, GSN. Publicly available data are available through common web services and via a cloud storage server (based on Swift). Collocation of the data and processing in the cloud would eventually eliminate data transfer requirements. Execution control logic Execution of the data analysis pipelines (for both the R-based analysis and the Alpine3D simulations) has been implemented using the GC3Pie framework developed by UZH. (https://code.google.com/p/gc3pie/). This allows large-scale, fault-tolerant execution of the pipelines to be described in terms of software appliances. GC3Pie also allows supervision of the execution of large campaigns of appliances as a single simulation. This poster will present the fundamental architectural components of the data analysis pipelines together with initial experimental results.

2013

Chargement

This thesis discusses replication of non-deterministic objects in distributed systems to achieve fault tolerance against crash failures. The objects replicated are the virtual nodes of a distributed application. Replication is viewed as an issue that is to be dealt with only during the configuration of a distributed application and that should not affect the development of the application. Hence, replication of virtual nodes should be transparent to the application. Like all measures to achieve fault tolerance, replication introduces redundancy in the system. Not surprisingly, the main difficulty is guaranteeing the consistency of all replicas such that they behave in the same way as if the object was not replicated (replication transparency). This is further complicated if active objects (like virtual nodes) are replicated, and these objects themselves can be clients of still further objects in the distributed application. The problems of replication of active non-deterministic objects are analyzed in the context of distributed Ada 95 applications. The ISO standard for Ada 95 defines a model for distributed execution based on remote procedure calls (RPC). Virtual nodes in Ada 95 use this as their sole communication paradigm, but they may contain tasks to execute activities concurrently, thus making the execution potentially non-deterministic due to implicit timing dependencies. Such non-determinism cannot be avoided by choosing deterministic tasking policies. I present two different approaches to maintain replica consistency despite this non-determinism. In a first approach, I consider the run-time support of Ada 95 as a black box (except for the part handling remote communications). This corresponds to a non-deterministic computation model. I show that replication of non-deterministic virtual nodes requires that remote procedure calls are implemented as nested transactions. Unfortunately, effects of failures are not local to the replicas of a virtual node: when a failure occurs, nested remote calls made to other virtual nodes must be undone. Also, using transactional semantics for RPCs necessitates a compromise regarding transparency: the application must identify global state for it cannot be determined reliably in an automatic way. Further study reveals that this approach cannot be implemented in a transparent way at all because the consistency criterion of Ada 95 (linearizability) is much weaker than that of transactions (serializability). An execution of remote procedure calls as transactions may thus lead to incompatibilities with the semantics of the programming language. If remotely called subprograms on a replicated virtual node perform partial operations, i.e., entry calls on global protected objects, deadlocks that cannot be broken can occur in certain cases. Such deadlocks do not occur when the virtual node is not replicated. The transactional semantics of RPCs must therefore be exposed to the application. A second approach is based on a piecewise deterministic computation model, i.e., the execution of a virtual node is seen as a sequence of deterministic state intervals. Whenever a non-deterministic event occurs, a new state interval is started. I study replica organization under this computation model (semi-active replication). In this model, all non-deterministic decisions are made on one distinguished replica (the leader), while all other replicas (the followers) are forced to follow the same sequence of non-deterministic events. I show that it suffices to synchronize the followers with the leader upon each observable event, i.e., when the leader sends a message to some other virtual node. It is not necessary to synchronize upon each and every non-deterministic event — which would incur a prohibitively high overhead. Non-deterministic events occurring on the leader between observable events are logged and sent to the followers just before the leader executes an observable event. Consequently, it is guaranteed that the followers will reach the same state as the leader, and thus the effects of failures remain mostly local to the replicas. A prototype implementation called RAPIDS (Replicated Ada Partitions In Distributed Systems) serves as a proof of concept for this second approach, demonstrating its feasibility. RAPIDS is an Ada 95 implementation of a replication manager for semi-active replication for the GNAT development system for Ada 95. It is entirely contained within the run-time support and hence largely transparent for the application.

EPFL1998

Chargement

Application of large-scale computing infrastructure for diverse environmental research applications using GC3Pie

Mathias Thierry Pierre Bavay, Michael Lehning, Sofiane Sarni

2013

EPFL1998

Complex event recognition through wearable sensors

Jean-Eudes Marie Ranvier

EPFL2017