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Publicações

Publicações por Luis Miguel Pinho

2015

Investigation on AUTOSAR-Compliant Solutions for Many-Core Architectures

Autores
Becker, M; Dasari, D; Nelis, V; Behnam, M; Pinho, LM; Nolte, T;

Publicação
2015 EUROMICRO CONFERENCE ON DIGITAL SYSTEM DESIGN (DSD)

Abstract
As of today, AUTOSAR is the de facto standard in the automotive industry, providing a common software architecture and development process for automotive applications. While this standard is originally written for singlecore operated Electronic Control Units (ECU), new guidelines and recommendations have been added recently to provide support for multicore architectures. This update came as a response to the steady increase of the number and complexity of the software functions embedded in modern vehicles, which call for the computing power of multicore execution environments. In this paper, we enumerate and analyze the design options and the challenges of porting AUTOSAR-based automotive applications onto multicore platforms. In particular, we investigate those options when considering the emerging many-core architectures that provide a more scalable environment than the traditional multicore systems. Such platforms are suitable to enable massive parallel execution, and their design is more suitable for partitioning and isolating the software components.

2015

A Multi-DAG Model for Real-Time Parallel Applications with Conditional Execution

Autores
Fonseca, JC; Nelis, V; Raravi, G; Pinho, LM;

Publicação
30TH ANNUAL ACM SYMPOSIUM ON APPLIED COMPUTING, VOLS I AND II

Abstract
Owing to the current trends for higher performance and the ever growing availability of multiprocessors in the embedded computing (EC) domain, there is nowadays a strong push towards the parallelization of modern embedded applications. Several real-time task models have recently been proposed to capture different forms of parallelism. However, they do not deal explicitly with control flow information as they assume that all the threads of a parallel task must execute every time the task is activated. In contrast, in this paper, we present a multi-DAG model where each task is characterized by a set of execution flows, each of which represents a different execution path throughout the task code and is modeled as a DAG of sub-tasks. We propose a two-step solution that computes a single synchronous DAG of servers for a task modeled by a multi-DAG and show that these servers are able to supply every execution flow of that task with the required cpu-budget so that the task can execute entirely, irrespective of the execution flow taken at run-time, while satisfying its precedence constraints. As a result, each task can be modeled by its single DAG of servers, which facilitates in leveraging the existing single-DAG schedulability analyses techniques for analyzing the schedulability of parallel tasks with multiple execution flows.

2016

The variability of application execution times on a multi-core platform

Autores
Nélis, V; Yomsi, PM; Pinho, LM;

Publicação
OpenAccess Series in Informatics

Abstract
It is a known fact that processes running concurrently on different cores in a multicore environment interfere with each other on the processor shared resources. The contention on these shared resources considerably slows down the execution on every core since sometimes the cores must stall while their requests to access the resources are being served. But by how much the execution may be slowed down due to this interference? In this paper we answer this question with numbers coming from experimentation. That is, we quantify the magnitude of the impact of the interference on the execution time by running programs taken from the TACLeBench benchmark suite, a popular benchmark suite in the real-time research community, on the first generation of Kalray manycore processor family, the MPPA-256 (the development board) that goes by the codename "Andey". © Vincent Nélis, Patrick Meumeu Yomsi and Luís Miguel Pinho.

2016

DYNAMIC CHARACTERIZATION OF INFILL MANSORY WALLS: IN-SITU AMBIENT VIBRATION TESTS

Autores
Pinho, M; Furtado, A; Rodrigues, H; Arede, A; Varum, H;

Publicação
IRF2016: 5TH INTERNATIONAL CONFERENCE INTEGRITY-RELIABILITY-FAILURE

Abstract
The present research work presents an experimental campaign of ambient vibration tests performed on twenty infill masonry walls from two buildings under construction and from another existent building. The main objective is to evaluate the influence of the boundary conditions, geometric dimensions, presence of openings with different dimensions as well as the existence of grooves along the wall for the installation of electrical cables, in the out-of-plane main frequencies of the infill walls tested. In the paper, it is presented a detailed description of the studied buildings, testing setups, equipment used, and further information regarding the walls tested. The main test results are presented and discussed.

2016

A Closer Look into the AER Model

Autores
Maia, C; Nogueira, L; Pinho, LM; Perez, DG;

Publicação
2016 IEEE 21ST INTERNATIONAL CONFERENCE ON EMERGING TECHNOLOGIES AND FACTORY AUTOMATION (ETFA)

Abstract
Commercial-of-the-shelf based multi-core systems present timing anomalies that cannot be ignored by the real-time systems community due to their unpredictable behaviour. These timing anomalies, often caused by applications' uncontrolled accesses to shared resources such as the components in the memory hierarchy or in the 1/0 subsystem, introduce interference that may lead to deadline misses if the problem is neglected. The Acquisition Execution Restitution (AER) execution model was previously proposed to circumvent this problem and, therefore, mitigate inter-task interference. In this model, applications decouple communication (acquisition and restitution phases) from the actual execution in a way that at most one acquisition or restitution phase is in execution at any instant of time while the execution phase of different tasks can progress in parallel on multiple cores. Thus, keeping each task's derived worst-case execution time closer to the one measured in isolation. In this paper, we study the AER execution model and compare it against a global Earliest Deadline First (EDF) approach where interferences are considered. Our results show that a priority assignment heuristic which assigns the priorities based on the tasks' periods dominates all the other proposed heuristics and that due to interference it can also schedule task sets which are not schedulable by using the global EDF approach.

2016

On Routing Flexibility of Wormhole-Switched Priority-Preemptive NoCs

Autores
Nikolic, B; Pinho, LM; Indrusiak, LS;

Publicação
2016 IEEE 22ND INTERNATIONAL CONFERENCE ON EMBEDDED AND REAL-TIME COMPUTING SYSTEMS AND APPLICATIONS (RTCSA)

Abstract
Flit-level preemptions via virtual channels have been proposed as one viable method to implement priority-preemptive arbitration policies in NoC routers, and integrate NoCs in the hard real-time domain. In recent years, researchers have explored several aspects of priority-preemptive NoCs, such as different arbitration techniques, different priority assignment methods (where applicable) and different workload mapping approaches, all with the common objective to use interconnect mediums more efficiently. Yet, the impact of different routing techniques on such a model is still an unexplored topic. Motivated by this reality, in this work we study the effects of routing flexibility on wormhole-switched priority-preemptive NoCs.

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