archimedes-Artificial Intelligence, Data Science, Algorithms-greece

 
Artificial Intelligence
 
Data Science
 
Algorithms

[Archimedes Mechanism Design Theme invited talk]Learning in Budgeted Auctions with Spacing Objectives

Dates
2025-01-22 14:30 - 16:00
Venue
Artemidos 1 - Amphitheater
Title: Learning in Budgeted Auctions with Spacing Objectives

Speaker: Giannis Fikioris (PhD Student at Cornell University, USA)

Abstract: In many repeated auction settings, participants care not only about how frequently they win but also how their winnings are distributed over time. This problem arises in various practical domains where avoiding congested demand is crucial, such as online retail sales and compute services, as well as in advertising campaigns that require sustained visibility over time. We introduce a simple model of this phenomenon, modeling it as a budgeted auction where the value of a win is a concave function of the time since the last win. This implies that for a given number of wins, even spacing over time is optimal. The goal is to maximize and evenly space conversions rather than just wins.

We study the optimal policies for this setting in second-price auctions and offer learning algorithms for the bidders that achieve low regret against the optimal bidding policy in a Bayesian online setting. Our main result is a computationally efficient online learning algorithm that achieves O(sqrt(T)) regret. We achieve this by showing that an infinite-horizon Markov decision process (MDP) with the budget constraint in expectation is essentially equivalent to our problem, even when limiting that MDP to a very small number of states. The algorithm achieves low regret by learning a bidding policy that chooses bids as a function of the context and the system's state, which will be the time elapsed since the last win (or conversion).

Short Bio: Giannis Fikioris  is a 5th-year PhD student in the department of Computer Science at Cornell University, advised by Eva Tardos. Before that, he got his diploma from NTUA, advised by Dimitris Fotakis. His interests include mainly Algorithmic Game Theory and Online Learning. Specifically, he has worked on Online Learning with Constraints, Online Resource Allocation, and Repeated Budgeted Auctions. His PhD has been supported by the NDSEG fellowship, the Onassis Scholarship, and the Google PhD fellowship.


You can attend remotely via MS-Teams through:

https://teams.microsoft.com/l/meetup-join/19%3ameeting_NzE4MjZkZGItZWE3NS00NzQ5LTk0OTItNWMzMzE3NjdkYjU4%40thread.v2/0?context=%7b%22Tid%22%3a%226ae07702-c5f7-4f38-9b87-acad62a75d93%22%2c%22Oid%22%3a%22700280a8-c91f-41bd-9bf8-38b7959b4a6f%22%7d   







 
 

Vision

To position Greece as a leading player in AI and Data Science

image
image

Mission

To build an AI Excellence Hub in Greece where the international research community can connect, groundbreaking ideas can thrive, and the next generation of scientists emerges, shaping a brighter future for Greece and the world

 

Welcome to ARCHIMEDES, a vibrant research hub connecting the global AI and Data Science research community fostering groundbreaking research in Greece and beyond. Its dedicated core team, comprising lead researchers, affiliated researchers, Post-Docs, PhDs and interns, is committed to advancing basic and applied research in Artificial Intelligence and its supporting disciplines, including Algorithms, Statistics, Learning Theory, and Game Theory organized around 8 core research areas. By collaborating with Greek and Foreign Universities and Research Institutes, ARCHIMEDES disseminates its research findings fostering knowledge exchange and providing enriching opportunities for students. Leveraging AI to address real-world challenges, ARCHIMEDES promotes innovation within the Greek ecosystem and extends its societal impact. Established in January 2022, as a research unit of the Athena Research Center with support from the Committee Greece 2021, ARCHIMEDES is funded for its first four years by the EU Recovery and Resilience Facility (RRF).

 
 

NEWS

 
Archimedes Seminar by Mark Girolami, Chief Scientist of the Alan Turing Institute, UK

Archimedes Seminar by Mark Girolami, Chief Scientist of the Alan Turing Institute, UK

27 October 2025

On Friday 7 November, 2025, from 1:00 pm to 2:00 pm, at the Archimedes Amphitheatre (1 Artemidos Street, 15125, Marousi, Archimedes, Athena Research Center, Greece), Mark Girolami, Sir Kirby Laing Professor of Civil Engineering within the Department of Engineering at the University of Cambridge, UK, where he also holds the Royal Academy of Engineering Research Chair in Data Centric Engineering, and Chief Scientist of the Alan Turing Institute, UK, will deliver an Archimedes Seminar on "Statistical Finite Element Methods."

Archimedes Talk by Alexandra Meliou on

Archimedes Talk by Alexandra Meliou on "Data Analysis and Manipulation through a Constrained Optimization Lens"

22 October 2025

On Tuesday 4 November, 2025, from 1:00 pm to 2:00 pm, at the Archimedes Amphitheatre (1 Artemidos Street, 15125, Marousi, Archimedes, Athena Research Center, Greece), Professor Alexandra Meliou, Professor at the College of Information and Computer Sciences at the University of Massachusetts Amherst, USA, and a visiting researcher at the Archimedes Research Unit, Athena Research Center, Greece, will deliver an Archimedes talk on "Data Analysis and Manipulation through a Constrained Optimization Lens."

Exploring the Frontiers of AI and Biomechanics at ICIST 2025

Exploring the Frontiers of AI and Biomechanics at ICIST 2025

20 October 2025

Archimedes, Athena Research Center, Greece is happy to see its work being featured at the 15th International Conference on Information Society and Technology (ICIST 2025), at Kaunas University of Technology, Lithuania, through an invited keynote speech by Dr. Serafeim Moustakidis, titled: “Bringing Biomechanics into the AI Era: A New Frontier for Gait and Joint Health.”

Archimedes Talk by Manos Athanassoulis on

Archimedes Talk by Manos Athanassoulis on "Harnessing the Untapped Benefits of Near-Sortedness for Data Systems"

14 October 2025

On Tuesday 21 October, 2025, from 1:00 pm to 2:00 pm, at the Archimedes Amphitheatre (1 Artemidos Street, 15125, Marousi, Archimedes, Athena Research Center, Greece), Professor Manos Athanassoulis, Associate Professor of Computer Science at Boston University (BU), USA, Director and Founder of the BU Data-intensive Systems and Computing Laboratory, BU, USA, and Co-Director of the BU Massive Data Algorithms and Systems Group, BU, USA, will deliver an Archimedes talk on "Harnessing the Untapped Benefits of Near-Sortedness for Data Systems."

GameSec 2025 just Around the Corner!

GameSec 2025 just Around the Corner!

9 October 2025

The 16th Conference on Game Theory and AI for Security (GameSec25), an event strongly supported by Archimedes, Athena Research Center, Greece will take place at the National Technical University of Athens, Greece from October 13-15 2025. "With the rapid advancement of artificial intelligence, game theory, and security technologies, the resilience and trustworthiness of modern systems is more critical than ever. The 2025 Conference on Game Theory and AI for Security focuses on leveraging strategic decision-making, adversarial reasoning, and computational intelligence to address security challenges in complex and dynamic environments.

More news items here
 
 

The project “ARCHIMEDES Unit: Research in Artificial Intelligence, Data Science and Algorithms” with code OPS 5154714 is implemented by the National Recovery and Resilience Plan “Greece 2.0” and is funded by the European Union – NextGenerationEU.

greece2.0 eu_arch_logo_en

 

Stay connected! Subscribe to our mailing list by emailing sympa@lists.athenarc.gr
with the subject "subscribe archimedes-news Firstname LastName"
(replace with your details)