Parallel and Distributed Systems Group

Computer Science Department of Telecom SudParis

PhD defense: Anatole Lefort, March 24th – A Support for Persistent Memory in Java


It is my pleasure to invite you all to the defense of my Ph.D. thesis,
prepared at Télécom SudParis and supervised by Pierre Sutra & Gaël Thomas.

    When: Friday, March 24 @ 9:30 A.M.
    Title: “A Support for Persistent Memory in Java”
    Virtual link:

It will be held in hybrid format - all details are available below.

Hope to see you there!


Anatole Lefort

--- Full Details ---

WHO: Anatole Lefort, Télécom SudParis

WHEN: Friday, March 24 @ 9:30 A.M.


   Amphi 7, Télécom (Sud)Paris
   19 place Marguerite Perey, 91120 Palaiseau, France
   Accès: Gare Massy-Palaiseau (TGV, RER) -> Bus 91.06.

TITLE: “A Support for Persistent Memory in Java”


Recently released non-volatile main memory (NVMM), as fast and durable
memory, dramatically increases storage performance over traditional
media (SSD, hard disk).
A substantial and unique property of NVMM is byte-addressability -
complex memory data structures, maintained with regular load/store
instructions, can now resist machine power-cycles, software faults or
system crashes.
However, correctly managing persistence with the fine grain of memory
instructions is laborious, with increased risk of compromising data
integrity and recovery at any misstep.
Programming abstractions from software libraries and support from
language runtime and compilers are necessary to avoid memory bugs that
are exacerbated with persistence.

In this thesis, we address the challenges of supporting persistent
memory in managed language environments by introducing J-NVM, a
framework to efficiently access NVMM in Java.
With J-NVM, we demonstrate how to design an efficient, simple and
complete interface to weave NVMM-devised persistence into
object-oriented programming, while remaining unobtrusive to the language
runtime itself.
In detail, J-NVM offers a fully-fledged interface to persist plain Java
objects using failure-atomic sections.
This interface relies internally on proxy objects that intermediate
direct off-heap access to NVMM.
The framework also provides a library of highly-optimized persistent
data types that resist reboots and power failures.
We evaluate J-NVM by implementing a persistent backend for Infinispan,
an industrial-grade data store.
Our experimental results, obtained with a TPC-B like benchmark and YCSB,
show that J-NVM is consistently faster than other approaches at
accessing NVMM in Java.


Mr. Paolo ROMANO, Associate Professor, University of Lisbon - Reviewer
Mr. Vivien QUEMA, Full Professor, Grenoble INP/ENSIMAG - Reviewer
Ms. Panagiota FATOUROU, Full Professor, University of Crete - Examiner
Ms. Sara BOUCHENAK, Full Professor, INSA Lyon - Examiner
Mr. Pierre SUTRA, Associate Professor, Télécom SudParis - Advisor
Mr. Gaël THOMAS, Full Professor, Télécom SudParis - Advisor

--- EOF ---

PhD defense: Alexis Colin – November, 28th – From trace collection to the prediction of the behaviour of parallel applications

Bonjour,J’ai le plaisir de vous inviter à ma soutenance de thèse intitulée “De la collecte de trace à la prédiction du comportement d’applications parallèles” [pdf]. Le résumé est disponible ci-dessous.

La soutenance aura lieu en français le lundi 28 novembre à 14h, dans l’amphithéâtre 3 des locaux de Télécom SudParis au 19 place Marguerite Perey, 91120 Palaiseau. Un accès en visioconférence sera disponible au lien suivant :

Le jury sera composé de :
– Mme Amel Bouzeghoub, Professeure – Télécom SudParis (Examinatrice)
– M. Patrick Carribault, Chercheur – CEA/DAM (Examinateur)
– M. Denis Conan, Maître de conférences HDR – Télécom SudParis (Directeur de thèse)
– Mme Camille Coti, Professeure – Université du Québec à Montréal (Rapporteuse)
– M. Arnaud Legrand, Directeur de recherche – INRIA Grenoble (Examinateur)
– M. Samuel Thibault, Professeur – Université de Bordeaux (Rapporteur)
– M. François Trahay, Maître de conférences HDR – Télécom SudParis (Encadrant)

La soutenance sera suivie d’un pot.

Résumé :

Afin d’exploiter les ressources des serveurs et des supercalculateurs, les développeurs ont recours à des modèles de programmations spécifiques qui sont mis en œuvre par des runtimes dont le rôle est de permettre à chaque programme d’exploiter pleinement les capacités de la machine qui l’exécute. Pour cela, les runtimes doivent prendre des décisions qui ont un impact direct sur les performances. Pour prendre de bonnes décisions, les runtimes essaient d’anticiper le comportement futur des programmes, mais les moyens à leur disposition sont limités.

Nous présentons Pythia, un oracle générique permettant aux runtimes de prédire le comportement futur d’un programme. Nous décrivons comment enregistrer une trace d’exécution d’un programme pour en capturer la structure sous la forme d’une grammaire. Nous développons un algorithme performant capable de construire une telle grammaire à la volée pendant l’exécution d’un programme sans dégrader ses performances. Nous montrons ensuite comment utiliser une grammaire représentant la structure d’une exécution d’un programme pour prédire son comportement futur lors de ses exécutions ultérieures. Pythia permet en particulier d’explorer un arbre probabilisé des prochaines actions potentielles d’un programme.

L’évaluation de notre travail montre que les prédictions de Pythia peuvent être utilisées pour implémenter des optimisations au sein d’un runtime. Nous faisons aussi la démonstration de l’utilisabilité de Pythia en l’utilisant pour mettre en œuvre une stratégie de parallélisme adaptatif au sein d’un runtime OpenMP existant.



Dear colleagues,

I have the pleasure to invite you to the defense of my PhD entitled “From trace collection to the prediction of the behaviour of parallel applications”. The abstract is below. The defense will take place in French on Monday, November 28 at 2:00 pm, in amphitheater 3 of the Télécom SudParis building at 19 place Marguerite Perey, 91120 Palaiseau. A videoconference access will be available at the following url:

The jury will be composed of:
– Mrs. Amel Bouzeghoub, Professor – Télécom SudParis (Examiner)
– Mr. Patrick Carribault, Researcher – CEA/DAM (Examiner)
– Mr. Denis Conan, Associate Professor HDR – Télécom SudParis (Director)
– Mrs. Camille Coti, Professor – Université du Québec à Montréal (Reviewer)
– Mr. Arnaud Legrand, Research director – INRIA Grenoble (Examiner)
– Mr. Samuel Thibault, Professor – Université de Bordeaux (Reviewer)
– Mr. François Trahay, Associate Professor HDR – Télécom SudParis (Co-director)

The defense will be followed by a buffet.


In order to exploit the resources of servers and supercomputers, developers use specific programming models that are implemented by runtimes. Runtimes allow each program to fully exploit the capacities of the machine that executes it. To do this, runtimes take decisions that have a direct impact on the performance of the programs. In order to take good decisions, runtimes try to anticipate the future behavior of the programs, but the means at their disposal are limited.

We present Pythia, a generic oracle allowing runtimes to predict the future behavior of a program. We describe how to record an execution trace and to capture its structure in the form of a grammar. We develop an algorithm capable of building such a grammar on the fly during the execution of a program without degrading its performance. We then show how to use a grammar representing the structure of a program execution to predict its future behavior during its subsequent executions. In particular, Pythia allows to explore a probabilized tree of potential next actions of a program.

The evaluation of our work shows that the predictions of Pythia can be used to implement optimizations within a runtime. We have also demonstrated the usability of Pythia by using it to implement an adaptive parallelism strategy within an existing OpenMP runtime.

Muktikanta Sa joined the PDS group as postdoc

Muktikanta Sa joined the PDS group as postdoc, welcome!

Mathieu Bacou joined the PDS group as associate professor

Mathieu Bacou joined the PDS group as associate professor, welcome!

Aurèle Maheo joined the PDS group as postdoc

Aurèle Maheo joined the PDS group as postdoc, welcome!

Yohan Pipereau, Damien Thenot, and Boubacar Kane joined the PDS group as PhD students

Yohan Pipereau, Damien Thenot, and Boubacar Kane joined the PDS group as PhD students. Welcome!