Scalable RDMA performance in PGAS languages

Partitioned global address space (PGAS) languages provide a unique programming model that can span shared-memory multiprocessor (SMP) architectures, distributed memory machines, or cluster ofSMPs. Users can program large scale machines with easy-to-use, shared memory paradigms. In order to exploit large scale machines efficiently, PGAS language implementations and their runtime system must be designed for scalability and performance. The IBM XLUPC compiler and runtime system provide a scalable design through the use of the shared variable directory (SVD). The SVD stores meta-information needed to access shared data. It is dereferenced, in the worst case, for every shared memory access, thus exposing a potential performance problem. In this paper we present a cache of remote addresses as an optimization that will reduce the SVD access overhead and allow the exploitation of native (remote) direct memory accesses. It results in a significant performance improvement while maintaining the run-time portability and scalability.Postprint (published version

An Escape Room For Learning Computer Programming

Game-based learning is a strategy where games are used as a challenge for students to learn and apply the contents of a subject matter. In this sense, game-based learning is an instance of problem-based learning. In this paper we discuss how game based strategies can be used to motivate students to perform the actions required for each of the learning phases. Namely: motivation, information, understanding, application and validation (feed-back). Then we present the application of those strategies to the design of an escape room where computer programs are required to solve the puzzles of the game. The designed escape room is then used as a game-based strategy in an introductory seminar on the Python programming language.Peer ReviewedPostprint (author's final draft

TXT as a vehicle for service learning

Service-learning is a method of teaching, learning and reflecting that combines academic classroom curriculum with meaningful service throughout the community. As a teaching methodology, it falls under the philosophy of experiential education. More specifically, it integrates meaningful community service with instruction and reflection to enrich the learning experience, teach civic responsibility, encourage lifelong civic engagement, and strengthen communities for the common good. Technology for everybody (TXT) is an association of people from the computer science and telecommunication schools at UPC. The main goal is to share our knowledge in Information and Communication Technology to communities that may benefit. In the last few years we have seen how technology has changed our everyday life and has became an inner part of a modern society. Lack of access to this knowledge enlarges the distance between communities. In this context, people in TXT aim to narrow the gap by providing technical knowledge to nongovernmental social institutions where this information could be useful. Another important task for TXT is building student's community awareness of international and local cooperation. The association tries to engage students into taking civil responsibilities, at the same time their learning experience are enriched. To that aim TxT runs the reuse workshop (among other projects); this initiative is managed by the Center of Cooperation and Development (CCD) the Technical University in Catalonia (UPC) and the association Technology for Everybody (TXT). It is a hands-on session where participants learn how to repair a computer.Peer Reviewe

Using shared-data localization to reduce the cost of inspector-execution in unified-parallel-C programs

Programs written in the Unified Parallel C (UPC) language can access any location of the entire local and remote address space via read/write operations. However, UPC programs that contain fine-grained shared accesses can exhibit performance degradation. One solution is to use the inspector-executor technique to coalesce fine-grained shared accesses to larger remote access operations. A straightforward implementation of the inspector executor transformation results in excessive instrumentation that hinders performance.; This paper addresses this issue and introduces various techniques that aim at reducing the generated instrumentation code: a shared-data localization transformation based on Constant-Stride Linear Memory Descriptors (CSLMADs) [S. Aarseth, Gravitational N-Body Simulations: Tools and Algorithms, Cambridge Monographs on Mathematical Physics, Cambridge University Press, 2003.], the inlining of data locality checks and the usage of an index vector to aggregate the data. Finally, the paper introduces a lightweight loop code motion transformation to privatize shared scalars that were propagated through the loop body.; A performance evaluation, using up to 2048 cores of a POWER 775, explores the impact of each optimization and characterizes the overheads of UPC programs. It also shows that the presented optimizations increase performance of UPC programs up to 1.8 x their UPC hand-optimized counterpart for applications with regular accesses and up to 6.3 x for applications with irregular accesses.Peer ReviewedPostprint (author's final draft

Game-based Learning in Computer Engineering: A Workshop

Gamification has gained popularity in the last years, it is used in primary and secondary schools, as well as in companies and universities (Call, 2021). Along with this growth in popularity the number of available computer tools that facilitate the implementation of quizzes, competitions, simulations, WebQuests etc. has also grown. Play engages students and enhances learning, however not all sorts of games are equally fruitful. As in (Dave Eng, 2019), we make a distinction between gamification and game-based learning (GBL). An example of gamification is a contest where students get points for solving the usual exercises of the subject matter. An example of game-based learning is an escape room where students get involved in studying and solving subject matter problems to get the required hints to continue the game. In this sense, game-based learning is an instance of problem-based learning (PBL) [Lima, 2017]. An interesting reflection on GBL can be found in [Valero, 2018]. The main objective of GBL is to provide an active learning environment, where students need to learn and apply the subject matter in order to participate and eventually solve the game. Compared with frontal lectures, active learning has been shown to provide higher motivation and deeper learning [Call, 2021] [Lopez-Fernandez, 2021]. From a general point of view, we can say that learning takes place in five stages [Bofill, 2007]. Namely: motivation, information retrieval, understanding, application (or practice) and reflection or feed-back. GBL, then, reinforces the autonomous realization of each of these stages. An escape room is a game where players must solve different puzzles and riddles in order to finish the game (in order to escape from the room). Escape rooms have been used extensively in education, since they allow for the organization of subject matter exercises in a pleasant way [Veldamp, 2020].Peer ReviewedPostprint (published version

An escape room for an alternative evaluation system

Our traditional education system spins around evaluation and its traditional grading system: summative assessment. In that system, professors spend time and effort trying to be “fair” when they mark the exercises, while students' main concern is snatching enough points to pass. We believe learning should be at the center. Students should put their energy on learning and professors on facilitating this learning process. However, we are still required to give a mark. We propose a game to achieve formative assessment. Play is a source of motivation to both engage students and enhance learning. The aim is that students should learn and enjoy their learning. We have designed an escape room with different sets of questions, each set corresponds to one topic. The student is presented with one activity to solve correctly. There is no grading but feedback: the answer can either be correct or incorrect. If the answer is correct, the student moves on to the next set of questions, otherwise the student is challenged with another activity of the same set. This goes on until the student solves one exercise correctly of each set. The student can only escape the room if one exercise of each topic is solved correctly. All activities proposed are of a basic level and if the student escapes the room he has a pass. Another bundle of sets can be done with more advanced exercises and if the student escapes the room he would achieve a higher mark. The method emphasizes two fundamental (but neglected) aspects of education: (i) the joy of learning; and (ii) diversity, as we give students as many opportunities as they need to learn at their own pace without penalty.This work has been supported by the Institut de Ciències de l’Educació (ICE) Convocatòria de projectes d’innovació docent 2021 (Acord CG/2021/02/34, de 9 d'abril de 2021) and by Escola Tècnica d’Enginyeria de Telecomunicació (upctelecos-BarcelonaTech).Peer ReviewedPostprint (published version

Game-based learning in computer engineering: a workshop

Gamification has gained popularity in the last years, it is used in primary and secondary schools, as well as in companies and universities (Call, 2021). Along with this growth in popularity the number of available computer tools that facilitate the implementation of quizzes, competitions, simulations, WebQuests etc. has also grown. Play engages students and enhances learning, however not all sorts of games are equally fruitful. As in (Dave Eng, 2019), we make a distinction between gamification and game-based learning (GBL). An example of gamification is a contest where students get points for solving the usual exercises of the subject matter. An example of game-based learning is an escape room where students get involved in studying and solving subject matter problems to get the required hints to continue the game. In this sense, game-based learning is an instance of problem-based learning (PBL) [Lima, 2017]. An interesting reflection on GBL can be found in [Valero, 2018]. The main objective of GBL is to provide an active learning environment, where students need to learn and apply the subject matter in order to participate and eventually solve the game. Compared with frontal lectures, active learning has been shown to provide higher motivation and deeper learning [Call, 2021] [Lopez-Fernandez, 2021]. From a general point of view, we can say that learning takes place in five stages [Bofill, 2007]. Namely: motivation, information retrieval, understanding, application (or practice) and reflection or feed-back. GBL, then, reinforces the autonomous realization of each of these stages. An escape room is a game where players must solve different puzzles and riddles in order to finish the game (in order to escape from the room). Escape rooms have been used extensively in education, since they allow for the organization of subject matter exercises in a pleasant way [Veldamp, 2020]

Game-based Learning vs Gamification: A Hands-On

An example of gamification is a contest where students get points for solving the usual exercises of the subject matter. An example of game-based learning is an escape room where students get involved in studying and solving subject matter problems to get the required hints to continue the game. In this sense, game-based learning is an instance of problem based learning. We propose a hand-on sesion where participants will get engaged into: first, a gamification activity; and later a game-based learning (GBL) activity. They will be encouraged to notice the differences and make a distinction between them. Afterwards, participants will be required to design a simple escape room situation involving problems for their own courses.Postprint (author's final draft

Exploring the predictability of MPI messages

Scalability to a large number of processes is one of the weaknesses of current MPI implementations. Standard implementations are able to scale to hundreds of nodes, but none beyond that. The main problem of current implementations is that performance is more important than scalability and thus some assumptions about resources are taken that will not scale well. The objective of the paper is twofold. On one hand, we show that characteristics such as the size and the sender of MPI messages are very predictable (accuracy above 90%). On the other hand, we present some examples where current MPI implementations would not work well when run on a large configuration and how this predictability could be used to solve the scalability problem.This work has been supported by the Ministry of Science and Technology of Spain and the European Union (FEDER funds) under contract TIC2001-0995-C02-01.Peer ReviewedPostprint (author's final draft