Federated Bandit

In this paper, we study Federated Bandit, a decentralized Multi-Armed Bandit problem with a set of N agents, who can only communicate their local data with neighbors described by a connected graph G. Each agent makes a sequence of decisions on selecting an arm from M candidates, yet they only have access to local and potentially biased feedback/evaluation of the true reward for each action taken. Learning only locally will lead agents to sub-optimal actions while converging to a no-regret strategy requires a collection of distributed data. Motivated by the proposal of federated learning, we aim for a solution with which agents will never share their local observations with a central entity, and will be allowed to only share a private copy of his/her own information with their neighbors. We first propose a decentralized bandit algorithm \textttGossip\_UCB, which is a coupling of variants of both the classical gossiping algorithm and the celebrated Upper Confidence Bound (UCB) bandit algorithm. We show that \textttGossip\_UCB successfully adapts local bandit learning into a global gossiping process for sharing information among connected agents, and achieves guaranteed regret at the order of O(\max\ \textttpoly (N,M) łog T, \textttpoly (N,M)łog_łambda_2^-1 N\ ) for all N agents, where łambda_2\in(0,1) is the second largest eigenvalue of the expected gossip matrix, which is a function of G. We then propose \textttFed\_UCB, a differentially private version of \textttGossip\_UCB, in which the agents preserve ε-differential privacy of their local data while achieving O(\max \\frac\textttpoly (N,M) ε łog^2.5 T, \textttpoly (N,M) (łog_łambda_2^-1 N + łog T) \ ) regret.

Short Stories, Poems, Letters

This chapter reviews the most neglected forms of Penelope Fitzgerald’s writing: her short stories, poems and letters. Although Fitzgerald claimed not to be able to write short stories, the evidence of the ten stories collected in The Means of Escape, and of the other eleven uncollected stories that survive, suggests otherwise. The chapter shows how Fitzgerald’s short fiction shares with her novels themes of misunderstanding, disappointment and loneliness. Other continuities include Fitzgerald’s tragicomic wit, art of compression, and taste for the macabre. Yet the chapter also shows how the stories differ from the novels. The sense of disruption of the accepted order of things is concentrated in the stories to the point of menace. The author’s presence, more pervasive and inescapable in the stories than in the novels, obscures the dividing line between author and narrator. By contrast, Fitzgerald’s handful of poems are surprisingly intimate and self-revealing, confronting the reader with a starker, more private version of Fitzgerald’s authorial persona. The letters, written to family, friends, literary editors and writers, provide a different kind of evidence of Fitzgerald’s sharp wit, intelligence and powers of observation.

Dzienniki Marii Dąbrowskiej: przygody człowieka etycznego

In analysing the complete diaries, the author points out that they are a specific form of personal document in which we encounter a doubly personalised approach to the world (through the author of the diaries and those who appear in the diary because they feature in her life). In the diary Dąbrowska is completely turned towards the world – primarily towards the other person (an exocentric, not egocentric, diary). It is from the point of view that the author describes four basic lines of tension in the diary – the private–public, the personal–social and historic, the internal–external, the conscious–subconscious, as well as its important function (keeping a balance of a situation of almost permanent crisis which is a part of the relationship between “me” and the world). Later, the author points to the most important components of Dąbrowska’s consciousness (the interrelated experiences of danger and the secrets of existence, the reality of the other person and its values and the undiminished ties which link people constituting a metaphysical and ethical component of their condition) and their sources (Abramowski, Conrad). The description of Dąbrowska identifies her embracing the “ethos of the democratic Polish intelligentsia” as well as her particular place within it. At the end the author emphasises that Dąbrowska’s private version as presented in the manuscripts of the diary is more authentic and real than the published version and that it demands the earliest possible publication of the whole diary in a philological edition (without footnotes), followed by academic work on it using the full critical apparatus.