Federated learning allows each client to keep its data locally when training machine learning models in a distributed setting. Significant recent research established the requirements that the input must satisfy in order to guarantee convergence of the training loop. This line of work uses averaging as the aggregation rule for the training models. In particular, we are interested in whether federated learning is robust to Byzantine behavior, and observe and investigate a tradeoff between the average/centroid and the validity conditions from distributed computing. We show that the various validity conditions alone do not guarantee a good approximation of the average. Furthermore, we show that reaching good approximation does not give good results in experimental settings due to possible Byzantine outliers. Our main contribution is the first lower bound of $\min\{\frac{n-t}{t},\sqrt{d}\}$ on the centroid approximation under box validity that is often considered in the literature, where $n$ is the number of clients, $t$ the upper bound on the number of Byzantine faults, and $d$ is the dimension of the machine learning model. We complement this lower bound by an upper bound of $2\min\{n,\sqrt{d}\}$, by providing a new analysis for the case $n

Al Jazeera drone video shows the widespread destruction of neighbourhoods in Khan Younis, an area of Gaza that was declared a'safe zone' for displaced Palestinians early in the war before Israeli forces later bombed and occupied it.

Iran's navy has released two American surface drones hours after seizing them in the Red Sea, accusing the unmanned vessels of jeopardising maritime safety, Iranian state television reports, in the second such incident this week. "The [Iranian navy] frigate Jamaran seized the two vessels on Thursday to prevent any possible accident after issuing warnings to the US fleet. After international shipping lanes were secured, the two vessels were released in a safe area," the state TV reported on Friday. Footage appeared to show more than a dozen Iranian navy personnel pushing two drones into the sea from the deck of their vessel – the latest maritime incident involving the United States Navy's new drone fleet in the Middle East as negotiations over Tehran's nuclear deal with the world powers hang in the balance. The state TV said an Iranian naval flotilla found "several unmanned spying vessels abandoned in the international maritime routes" and "after warning an American destroyer twice, seized the two drone vessels to prevent possible accidents".

When learning to ride a bike, a child falls down a number of times before achieving the first success. As falling down usually has only mild consequences, it can be seen as a tolerable failure in exchange for a faster learning process, as it provides rich information about an undesired behavior. In the context of Bayesian optimization under unknown constraints (BOC), typical strategies for safe learning explore conservatively and avoid failures by all means. On the other side of the spectrum, non conservative BOC algorithms that allow failing may fail an unbounded number of times before reaching the optimum. In this work, we propose a novel decision maker grounded in control theory that controls the amount of risk we allow in the search as a function of a given budget of failures. Empirical validation shows that our algorithm uses the failures budget more efficiently in a variety of optimization experiments, and generally achieves lower regret, than state-of-the-art methods. In addition, we propose an original algorithm for unconstrained Bayesian optimization inspired by the notion of excursion sets in stochastic processes, upon which the failures-aware algorithm is built.

Finding the optimum path for a robot for moving from start to the goal position through obstacles is still a challenging issue. Thi s paper presents a novel path planning method, named D - point trigonometric, based on Q - learning algorithm for dynamic and uncertain environments, in which all the obstacles and the target are moving. We define a new state, action and reward functions for t he Q - learning by which the agent can find the best action in every state to reach the goal in the most appropriate path. Moreover, the experiment s in Unity3D confirmed the high convergence speed, the high hit rate, as well as the low dependency on environmental parameters of the proposed method compared with an opponent approach. The planning has been considered as a challenging concern in video games [1], transportation systems [2], and mobile robots [3] [4] . A s the most important path planning issues, w e can refer to the dynamics and the uncertainty of the environment, the smoothness and the length of the path, obstacle avoidance, and the computation al cost . In the last few decades, researchers have done numerous research efforts to present new approaches to solve them [5] [6] [7] [8] . Generally, most of the path planning approaches are categorized to one of the following methods [9] [10] [11]: ( 1) Classical methods (a) Computational geometry (CG) (b) Probabilistic r oadmap (PRM) (c) Potential fields method (PFM) ( 2) Heuristic and meta heuristic methods (a) Soft computing (b) Hybrid algorithms Since the complexity and the execution time of CG methods were high [11], PRMs were proposed to red uce the search space using techniques like milestones [12] .

Social attachment theory states that individuals seek the proximity of attachment figures (e.g. family members, friends, colleagues, familiar places or objects) when faced with threat. During disasters, this means that family members may seek each other before evacuating, gather personal property before heading to familiar exits and places, or follow groups/crowds, etc. This hard-wired human tendency should be considered in the assessment of risk and the creation of disaster management plans. Doing so may result in more realistic evacuation procedures and may minimise the number of casualties and injuries. In this context, a dynamic spatio-temporal analysis of seismic risk is presented using SOLACE, a multi-agent model of pedestrian behaviour based on social attachment theory implemented using the Belief-Desire-Intention approach. The model focuses on the influence of human, social, physical and temporal factors on successful evacuation. Human factors considered include perception and mobility defined by age. Social factors are defined by attachment bonds, social groups, population distribution, and cultural norms. Physical factors refer to the location of the epicentre of the earthquake, spatial distribution/layout and attributes of environmental objects such as buildings, roads, barriers (cars), placement of safe areas, evacuation routes, and the resulting debris/damage from the earthquake. Experiments tested the influence of time of the day, presence of disabled persons and earthquake intensity. Initial results show that factors that influence arrivals in safe areas include (a) human factors (age, disability, speed), (b) pre-evacuation behaviours, (c) perception distance (social attachment, time of day), (d) social interaction during evacuation, and (e) physical and spatial aspects, such as limitations imposed by debris (damage), and the distance to safe areas. To validate the results, scenarios will be designed with stakeholders, who will also take part in the definition of a serious game. The recommendation of this research is that both social and physical aspects should be considered when defining vulnerability in the analysis of risk.