35,343 research outputs found
Towards Ad Hoc Recovery for Soft Errors
The coming exascale era is a great opportunity for high performance computing (HPC) applications. However, high failure rates on these systems will hazard the successful completion of their execution. Bit-flip errors in dynamic random access memory (DRAM) account for a noticeable share of the failures in supercomputers. Hardware mechanisms, such as error correcting code (ECC), can detect and correct single-bit errors and can detect some multi-bit errors while others can go undiscovered. Unfortunately, detected multi-bit errors will most of the time force the termination of the application and lead to a global restart. Thus, other strategies at the software level are needed to tolerate these type of faults more efficiently and to avoid a global restart. In this work, we extend the FTI checkpointing library to facilitate the implementation of custom recovery strategies for MPI applications, minimizing the overhead introduced when coping with soft errors. The new functionalities are evaluated by implementing local forward recovery on three HPC benchmarks with different reliability requirements. Our results demonstrate a reduction on the recovery times by up to 14%.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 708566 (DURO). This research is also supported by the Ministry of Economy and Competitiveness of Spain and FEDER funds of
the EU (Projects TIN2016-75845-P and the predoctoral grant of Nuria Losada ref. BES-2014-068066), and by the Galician
Government (Xunta de Galicia) under the Consolidation Program of Competitive Research (ref. ED431C 2017/04).Peer ReviewedPostprint (author's final draft
Recommended from our members
Software safety : a definition and some preliminary thoughts
Software safety is the subject of a research project in its initial stages at the University of California Irvine. This research deals with critical real-time software where the cost of an error is high, e.g. human life. In this paper software techniques having a bearing on safety are described and evaluated. Initial definitions of software safety concepts are presented along with some preliminary thoughts and research questions
A novel cooperative opportunistic routing scheme for underwater sensor networks
Increasing attention has recently been devoted to underwater sensor networks (UWSNs) because of their capabilities in the ocean monitoring and resource discovery. UWSNs are faced with different challenges, the most notable of which is perhaps how to efficiently deliver packets taking into account all of the constraints of the available acoustic communication channel. The opportunistic routing provides a reliable solution with the aid of intermediate nodes’ collaboration to relay a packet toward the destination. In this paper, we propose a new routing protocol, called opportunistic void avoidance routing (OVAR), to address the void problem and also the energy-reliability trade-off in the forwarding set selection. OVAR takes advantage of distributed beaconing, constructs the adjacency graph at each hop and selects a forwarding set that holds the best trade-off between reliability and energy efficiency. The unique features of OVAR in selecting the candidate nodes in the vicinity of each other leads to the resolution of the hidden node problem. OVAR is also able to select the forwarding set in any direction from the sender, which increases its flexibility to bypass any kind of void area with the minimum deviation from the optimal path. The results of our extensive simulation study show that OVAR outperforms other protocols in terms of the packet delivery ratio, energy consumption, end-to-end delay, hop count and traversed distance
Application-level Fault Tolerance and Resilience in HPC Applications
Programa Oficial de Doutoramento en Investigación en Tecnoloxías da Información. 524V01[Resumo]
As necesidades computacionais das distintas ramas da ciencia medraron enormemente
nos últimos anos, o que provocou un gran crecemento no rendemento proporcionado
polos supercomputadores. Cada vez constrúense sistemas de computación
de altas prestacións de maior tamaño, con máis recursos hardware de distintos tipos,
o que fai que as taxas de fallo destes sistemas tamén medren. Polo tanto, o
estudo de técnicas de tolerancia a fallos eficientes é indispensábel para garantires
que os programas científicos poidan completar a súa execución, evitando ademais
que se dispare o consumo de enerxía. O checkpoint/restart é unha das técnicas máis
populares. Sen embargo, a maioría da investigación levada a cabo nas últimas décadas
céntrase en estratexias stop-and-restart para aplicacións de memoria distribuída
tralo acontecemento dun fallo-parada. Esta tese propón técnicas checkpoint/restart
a nivel de aplicación para os modelos de programación paralela roáis populares en
supercomputación. Implementáronse protocolos de checkpointing para aplicacións
híbridas MPI-OpenMP e aplicacións heteroxéneas baseadas en OpenCL, en ámbolos
dous casos prestando especial coidado á portabilidade e maleabilidade da solución.
En canto a aplicacións de memoria distribuída, proponse unha solución de resiliencia
que pode ser empregada de forma xenérica en aplicacións MPI SPMD, permitindo
detectar e reaccionar a fallos-parada sen abortar a execución. Neste caso, os procesos
fallidos vólvense a lanzar e o estado da aplicación recupérase cunha volta atrás global.
A maiores, esta solución de resiliencia optimizouse implementando unha volta
atrás local, na que só os procesos fallidos volven atrás, empregando un protocolo de
almacenaxe de mensaxes para garantires a consistencia e o progreso da execución.
Por último, propónse a extensión dunha librería de checkpointing para facilitares a implementación de estratexias de recuperación ad hoc ante conupcións de memoria.
En moitas ocasións, estos erros poden ser xestionados a nivel de aplicación, evitando
desencadear un fallo-parada e permitindo unha recuperación máis eficiente.[Resumen]
El rápido aumento de las necesidades de cómputo de distintas ramas de la ciencia
ha provocado un gran crecimiento en el rendimiento ofrecido por los supercomputadores.
Cada vez se construyen sistemas de computación de altas prestaciones mayores,
con más recursos hardware de distintos tipos, lo que hace que las tasas de
fallo del sistema aumenten. Por tanto, el estudio de técnicas de tolerancia a fallos
eficientes resulta indispensable para garantizar que los programas científicos puedan
completar su ejecución, evitando además que se dispare el consumo de energía. La
técnica checkpoint/restart es una de las más populares. Sin embargo, la mayor parte
de la investigación en este campo se ha centrado en estrategias stop-and-restart
para aplicaciones de memoria distribuida tras la ocurrencia de fallos-parada. Esta
tesis propone técnicas checkpoint/restart a nivel de aplicación para los modelos de
programación paralela más populares en supercomputación. Se han implementado
protocolos de checkpointing para aplicaciones híbridas MPI-OpenMP y aplicaciones
heterogéneas basadas en OpenCL, prestando en ambos casos especial atención a la
portabilidad y la maleabilidad de la solución. Con respecto a aplicaciones de memoria
distribuida, se propone una solución de resiliencia que puede ser usada de forma
genérica en aplicaciones MPI SPMD, permitiendo detectar y reaccionar a fallosparada
sin abortar la ejecución. En su lugar, se vuelven a lanzar los procesos fallidos
y se recupera el estado de la aplicación con una vuelta atrás global. A mayores, esta
solución de resiliencia ha sido optimizada implementando una vuelta atrás local, en
la que solo los procesos fallidos vuelven atrás, empleando un protocolo de almacenaje
de mensajes para garantizar la consistencia y el progreso de la ejecución. Por
último, se propone una extensión de una librería de checkpointing para facilitar la
implementación de estrategias de recuperación ad hoc ante corrupciones de memoria.
Muchas veces, este tipo de errores puede gestionarse a nivel de aplicación, evitando
desencadenar un fallo-parada y permitiendo una recuperación más eficiente.[Abstract]
The rapid increase in the computational demands of science has lead to a pronounced
growth in the performance offered by supercomputers. As High Performance
Computing (HPC) systems grow larger, including more hardware components
of different types, the system's failure rate becomes higher. Efficient fault
tolerance techniques are essential not only to ensure the execution completion but
also to save energy. Checkpoint/restart is one of the most popular fault tolerance
techniques. However, most of the research in this field is focused on stop-and-restart
strategies for distributed-memory applications in the event of fail-stop failures. Thís
thesis focuses on the implementation of application-level checkpoint/restart solutions
for the most popular parallel programming models used in HPC. Hence, we
have implemented checkpointing solutions to cope with fail-stop failures in hybrid
MPI-OpenMP applications and OpenCL-based programs. Both strategies maximize
the restart portability and malleability, ie., the recovery can take place on
machines with different CPU / accelerator architectures, and/ or operating systems,
and can be adapted to the available resources (number of cores/accelerators). Regarding
distributed-memory applications, we propose a resilience solution that can
be generally applied to SPMD MPI programs. Resilient applications can detect and
react to failures without aborting their execution upon fail-stop failures. Instead,
failed processes are re-spawned, and the application state is recovered through a
global rollback. Moreover, we have optimized this resilience proposal by implementing
a local rollback protocol, in which only failed processes rollback to a previous
state, while message logging enables global consistency and further progress of the
computation. Finally, we have extended a checkpointing library to facilitate the
implementation of ad hoc recovery strategies in the event of soft errors) caused by
memory corruptions. Many times, these errors can be handled at the software-Ievel,
tIms, avoiding fail-stop failures and enabling a more efficient recovery
Adaptive Process Management in Cyber-Physical Domains
The increasing application of process-oriented approaches in new challenging cyber-physical domains beyond business computing (e.g., personalized healthcare, emergency management, factories of the future, home automation, etc.) has led to reconsider the level of flexibility and support required to manage complex processes in such domains. A cyber-physical domain is characterized by the presence of a cyber-physical system coordinating heterogeneous ICT components (PCs, smartphones, sensors, actuators) and involving real world entities (humans, machines, agents, robots, etc.) that perform complex tasks in the “physical” real world to achieve a common goal. The physical world, however, is not entirely predictable, and processes enacted in cyber-physical domains must be robust to unexpected conditions and adaptable to unanticipated exceptions. This demands a more flexible approach in process design and enactment, recognizing that in real-world environments it is not adequate to assume that all possible recovery activities can be predefined for dealing with the exceptions that can ensue. In this chapter, we tackle the above issue and we propose a general approach, a concrete framework and a process management system implementation, called SmartPM, for automatically adapting processes enacted in cyber-physical domains in case of unanticipated exceptions and exogenous events. The adaptation mechanism provided by SmartPM is based on declarative task specifications, execution monitoring for detecting failures and context changes at run-time, and automated planning techniques to self-repair the running process, without requiring to predefine any specific adaptation policy or exception handler at design-time
- …