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Different shades of green on small islands

Teresa Tiago, Sandra Dias Faria, João Luís Cogumbreiro, João Pedro Couto, Flávio Tiago
2016 Island Studies Journal  
Introduction The earth contains approximately 180,497 islands of different sizes, political frameworks, geographical positions and natural resources (Tiago, Tiago & Amaral, 2015) .  ... 
doaj:11f956d5dc454bcd8d96978a9f8031d4 fatcat:2v7nfihwerhc3cwwloigdwufnq

Checking Data-Race Freedom of GPU Kernels, Compositionally (Artifact) [article]

Tiago Cogumbreiro, Julien Lange, Dennis Liew Zhen Rong, Hannah Zicarelli
2021 Zenodo  
The artifact of the CAV 2021 paper entitled "Checking Data-Race Freedom of GPU Kernels, Compositionally".
doi:10.5281/zenodo.4726300 fatcat:unawnvlgvvc7ljhhhbzqxjizne

Coordinating Phased Activities while Maintaining Progress [chapter]

Tiago Cogumbreiro, Francisco Martins, Vasco Thudichum Vasconcelos
2013 Lecture Notes in Computer Science  
In order to develop reliable applications for parallel machines, programming languages and systems need to provide for flexible parallel programming coordination techniques. Barriers, clocks and phasers constitute promising synchronisation mechanisms, but they exhibit intricate semantics and allow writing programs that can easily deadlock. We present an operational semantics and a type system for a fork/join programming model equipped with a flexible variant of phasers. Our proposal allows for
more » ... precise control over the maximum number of synchronisation steps each task can be ahead of others. A type system ensures that programs do not deadlock, even when they use multiple phasers.
doi:10.1007/978-3-642-38493-6_3 fatcat:qpsmcnw7rvftbiurp7vkpvm5rq

Dynamic deadlock verification for general barrier synchronisation

Tiago Cogumbreiro, Raymond Hu, Francisco Martins, Nobuko Yoshida
2015 SIGPLAN notices  
Cogumbreiro et al. [8] propose a static typing system to ensure the correctness of phased activities for a fragment of X10 that disallows awaiting on a particular clock.  ... 
doi:10.1145/2858788.2688519 fatcat:tn3tnmgbhba4dpojydqrpxeiam

Formalization of Phase Ordering

Tiago Cogumbreiro, Jun Shirako, Vivek Sarkar
2016 Electronic Proceedings in Theoretical Computer Science  
Phasers pose an interesting synchronization mechanism that generalizes many collective synchronization patterns seen in parallel programming languages, including barriers, clocks, and point-to-point synchronization using latches or semaphores. This work characterizes scheduling constraints on phaser operations, by relating the execution state of two tasks that operate on the same phaser. We propose a formalization of Habanero phasers, May-Happen-In-Parallel, and Happens-Before relations for
more » ... er operations, and show that these relations conform with the semantics. Our formalization and proofs are fully mechanized using the Coq proof assistant, and are available online.
doi:10.4204/eptcs.211.2 fatcat:5aefxhn67fhgvcltnxbgcgqfoi

Types for X10 Clocks

Francisco Martins, Vasco T. Vasconcelos, Tiago Cogumbreiro
2011 Electronic Proceedings in Theoretical Computer Science  
X10 is a modern language built from the ground up to handle future parallel systems, from multicore machines to cluster configurations. We take a closer look at a pair of synchronisation mechanisms: finish and clocks. The former waits for the termination of parallel computations, the latter allow multiple concurrent activities to wait for each other at certain points in time. In order to better understand these concepts we study a type system for a stripped down version of X10. The main result
more » ... ssures that well typed programs do not run into the errors identified in the X10 language reference, namely the ClockUseException. The study will open, we hope, doors to a more flexible utilisation of clocks in the X10 language.
doi:10.4204/eptcs.69.8 fatcat:e57mj3orxva3bfowxpjyth26dy

Checking Data-Race Freedom of GPU Kernels, Compositionally [chapter]

Tiago Cogumbreiro, Julien Lange, Dennis Liew Zhen Rong, Hannah Zicarelli
2021 Lecture Notes in Computer Science  
AbstractGPUs offer parallelism as a commodity, but they are difficult to program correctly. Static analyzers that guarantee data-race freedom (DRF) are essential to help programmers establish the correctness of their programs (kernels). However, existing approaches produce too many false alarms and struggle to handle larger programs. To address these limitations we formalize a novel compositional analysis for DRF, based on access memory protocols. These protocols are behavioral types that
more » ... the way threads interact over shared memory.Our work includes fully mechanized proofs of our theoretical results, the first mechanized proofs in the field of DRF analysis for GPU kernels. Our theory is implemented in , a tool that outperforms the state-of-the-art. Notably, it can correctly verify at least $$1.42{\times }$$ 1.42 × more real-world kernels, and it exhibits a linear growth in 4 out of 5 experiments, while others grow exponentially in all 5 experiments.
doi:10.1007/978-3-030-81685-8_19 fatcat:ny7z6swaivbpdlrbvlfeqgf4eq

Compiling the π-calculus into a Multithreaded Typed Assembly Language

Tiago Cogumbreiro, Francisco Martins, Vasco T. Vasconcelos
2009 Electronical Notes in Theoretical Computer Science  
We extend a previous work on a multithreaded typed assembly language (MIL) targeted at shared memory multiprocessors, and describe the design of a type-preserving compiler from the π-calculus into MIL. The language enforces a policy on lock usage through a typing system that also ensures race-freedom for typable programs, while allowing for typing various important concurrency patterns. Our translation to MIL generates code that is then linked to a library supporting a generic unbounded buffer
more » ... onitor, variant of Hoare's bounded buffer monitor, entirely written in MIL. Such a monitor shields client code (the π-calculus compiler in particular) from the hazardous task of direct lock manipulation, while allowing for the representation of π-calculus channels. The compiler produces type correct MIL programs from type correct source code, generating low-contention cooperative multithreaded programs.
doi:10.1016/j.entcs.2009.06.004 fatcat:4epbszgohneqtbwmszx3wjjere


Tiago Cogumbreiro, Gregory Blike
2022 Proceedings of the 27th ACM Conference on on Innovation and Technology in Computer Science Education Vol. 1  
Generating visualizations of Formal Languages and Automata (FLA) is often a laborious and error prone task. Existing tools either offer the ability to fully customize the appearance of the artifacts, or offer reusability and abstraction, but do not offer both at the same time. In this paper, we introduce a system called Gidayu for creating mathematical diagrams of automata, of their computations, and of their transformations. Many kinds of automata are supported: (non)deterministic finite
more » ... ta, generalized nondeterministic finite automata, and (non)-deterministic pushdown automata. Gidayu fosters experimentation and rapid prototyping, as diagrams are generated automatically. The specification language includes directives to fine tune the presentation of each element; and, users can customize the visual notation used by our system. We discuss various parameters Gidayu offers to visualize diagrams and their importance in the instruction of FLA. CCS CONCEPTS • Human-centered computing → Visualization toolkits; Visualization design and evaluation methods; • Theory of computation → Regular languages.
doi:10.1145/3502718.3524742 fatcat:pjtnhealbbfw3aenrlued67a4a

Provable GPU Data-Races in Static Race Detection

Dennis Liew, Tiago Cogumbreiro, Julien Lange
2022 Electronic Proceedings in Theoretical Computer Science  
We extend the theory behind the Faial tool-chain, which can soundly prove that CUDA programs (aka, kernels) are data-race free using specialized behavioral types called memory access protocols (MAPs). In this paper we extend the theory of MAPs to characterize kernels for which alarms can be identified as true alarms. We introduce a core calculus for CUDA, which we named BabyCUDA, and a behavioral type system for it. We show that if a BabyCUDA program can be assigned a MAP, then any alarm raised by Faial for this program is a true alarm.
doi:10.4204/eptcs.356.4 fatcat:q2qqrwmz5nhwxcdadja5uo3ktq

Dynamic deadlock verification for general barrier synchronisation

Tiago Cogumbreiro, Raymond Hu, Francisco Martins, Nobuko Yoshida
2015 Proceedings of the 20th ACM SIGPLAN Symposium on Principles and Practice of Parallel Programming - PPoPP 2015  
Cogumbreiro et al. [8] propose a static typing system to ensure the correctness of phased activities for a fragment of X10 that disallows awaiting on a particular clock.  ... 
doi:10.1145/2688500.2688519 dblp:conf/ppopp/CogumbreiroHMY15 fatcat:zpos24esf5hgnjhvhiyvfbfk7y

Type Inference for Deadlock Detection in a Multithreaded Polymorphic Typed Assembly Language

Vasco T. Vasconcelos, Francisco Martins, Tiago Cogumbreiro
2010 Electronic Proceedings in Theoretical Computer Science  
We previously developed a polymorphic type system and a type checker for a multithreaded lock-based polymorphic typed assembly language (MIL) that ensures that well-typed programs do not encounter race conditions. This paper extends such work by taking into consideration deadlocks. The extended type system verifies that locks are acquired in the proper order. Towards this end we require a language with annotations that specify the locking order. Rather than asking the programmer (or the
more » ... 's backend) to specifically annotate each newly introduced lock, we present an algorithm to infer the annotations. The result is a type checker whose input language is non-decorated as before, but that further checks that programs are exempt from deadlocks.
doi:10.4204/eptcs.17.8 fatcat:ksnwj4lbfncejklfxun55nnfsu


Vanda Nascimento
2017 Movimento (ESEFID/UFRGS)  
Dando corpo à reflexão que se vem apresentando sobre o corpo na dança, transcrevemos as palavras de Tiago Rodrigues constantes da folha de sala do espetáculo: [...]  ...  Essa peça, escrita e dirigida por Tiago Rodrigues (ator, encenador e dramaturgo português), em diálogo permanente com música original e ao vivo de Mário Laginha (compositor e pianista português), desenvolve-se  ... 
doi:10.22456/1982-8918.71021 fatcat:vbbufowqvjfvdnbhz2sa7vkxam

Artifact Evaluation Experience CGO'15 / PPoPP'15

Grigori Fursin
2019 Zenodo  
Cogumbreiro, Raymond Hu, Francisco Martins and Nobuko Yoshida •Low-Overhead Software Transactional Memory with Progress Guarantees and Strong Semantics Minjia Zhang, Jipeng Huang, Man Cao and Michael  ...  Implementation of 3D Unstructured Meshes Computation: A Case Study on Matrix Assembly Loïc Thébault, Eric Petit and Quang Dinh •Dynamic deadlock verification for general barrier synchronisation Tiago  ... 
doi:10.5281/zenodo.2544246 fatcat:563x3tktpze3zpnw4cbtmr7t2e

Digital sustainability communication in tourism

Flavio Tiago, Artur Gil, Sara Stemberger, Teresa Borges-Tiago
2020 Journal of Innovation & Knowledge  
A similar situation was reported by Tiago, Faria, Cogumbreiro, Couto, and Tiago (2016) ; they emphasized that not all tourists value the green efforts of lodging firms.  ...  Nevertheless, some tourism stakeholders emphasize the challenges in promoting and creating value from sustainable practices on small islands (Tiago et al., 2016) , highlighting inadequate access to revenue  ... 
doi:10.1016/j.jik.2019.12.002 fatcat:ebyi6q7cvbgrvfvqaz6dn3stzu
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