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People of ACM - Jeannette Wing (2014)

In order to explore the fundamental trade-off between delay performance and implementation overhead, we consider an asymptotic regime where the total arrival rate and number of servers N grow large in proportion and the diversity parameter d(N) depends on N. We show that the fluid limit and the diffusion limit correspond to those for the ordinary JSQ policy when d(N) tends to infinity and d(N) / (sqrt(N) log(N)) tends to infinity, respectively, as the number of servers N grows large. Thus, the optimality of the JSQ policy can be retained at fluid level and diffusion level while reducing the amount of communication overhead by nearly a factor N and sqrt(N) / log(N), respectively. In addition, we analyze load balancing mechanisms which leverage memory at the dispatcher in order to reduce the amount of communication overhead further while maintaining low delay.

A key facet of the supermarket model is that any task can be handled equally efficiently by any server, which provides analytical tractability but does not cover situations where the processing speeds of a specific task at the various servers may be different. These scenarios may arise due to data locality, task-server affinity relations, or broader compatibility constraints. In order to capture such heterogeneity features, we broaden the attention to network scenarios where the various servers are interconnected by some underlying graph topology G_N. Tasks arrive with rate lambda at each of the N servers, and each task is assigned to the server with the shortest queue among the one where it appears and its neighbors in the graph G_N. We establish conditions - in terms of the average degree and structure of the graph G_N - for the fluid-scaled and diffusion-scaled occupancy processes to be equivalent to those for the case of a clique. The results demonstrate that the optimality of a clique can be asymptotically achieved with far fewer connections, provided the graph topology G_N is suitably random.

- quantum computers will be able to simulate physical systems that are hard to simulate classically (with applications to materials and chemistry);
- quantum computers will be able to factor large numbers and, therefore, break the currently used public key cryptosystems such as RSA;
- quantum computers will provide speedup for a variety of search problems, from naive exhaustive search to finding the best move in 2 player games.
I will describe these three big applications, with an emphasis of search problems.

Andris Ambainis is one of the leading experts in the world in computer science aspects of quantum computing. He has made many important contributions, from quantum walks (quantum counterparts of random walks) as one of main methods for quantum algorithms to "quantum adversary" method for proving optimality of quantum algorithms.

Cláudia is going to talk mainly about "paires d'amis" (couple of friends or even pair) as their main results were about friendship, explaining how "paires d'amis" can be used to color graphs. She is going to remember their search for "pair d'amis" in planar graphs, claw-free graphs, dart-free graphs and C_4-free graphs, and how they turn their search to mesure the quality of the greedy and b-heuristics colorings, already together with Ana.

Ana Shirley F. da Silva é professora no Departamento de Matemática da Universidade Federal do Ceará. Ela obteve seu título de doutora em 2010 também sob a supervisão de Frédéric Maffray na Université de Grenoble, França, e passou um ano com bolsa de pós-doutorado no Centrum Wiskunde & Informatica, Amsterdã, entre 2015 e 2016. Ela é bolsista de produtividade nível 2 e trabalha principalmente com problemas de coloração em grafos.

The term Blockchain 2.0 refers to new applications of the blockchain to go beyond transactions and enable exchange of assets without powerful intermediaries. Examples of applications are smart contracts, persistent digital ids, intellectual property rights, blogging, voting, reputation, etc. Blockchain 2.0 could dramatically cut down transaction costs, by automating operations and removing intermediaries. It could allow people to monetize their own information and creators of intellectual property to be properly compensated. The potential impact on society is huge, as excluded people could join freely the global economy.