Abstract
Program termination is a key question in program verification. This talk considers the termination of probabilistic programs, programs that can describe e.g., randomized algorithms, security algorithms and Bayesian learning.

Probabilistic termination has several nuances. Diverging program runs may occur with probability zero. Such programs are almost surely terminating (AST). If the expected duration until termination is finite, they are positive AST.

This talk presents the different nuances of probabilistic termination and discusses the hardness (how undecidable are these notions?) to check these properties.

To conclude we will present a simple proof rule for deciding AST, and reports on recent approaches towards automation to check whether a program is AST, PAST, non-AST, non-PAST, or “don’t know”.

The event takes place on Zoom:

https://rwth.zoom.us/j/96043715437?pwd=U0dRczkyQjRCY21abW13TDNmUHlhUT09
Meeting ID: 960 4371 5437
Passcode: 039217

Since the event is open also to master's students, who may not receive this email, we would kindly appreciate if you could pass this invitation on.

We are looking forward to seeing many of you at the survey lecture.

Best regards,
Tim Seppelt for the organisation committee

-------- Forwarded Message --------

Subject:	UnRAVeL "Behind the Scenes" Survey Lecture
Date:	Fri, 19 Mar 2021 10:43:09 +0100
From:	Tim Seppelt <seppelt@cs.rwth-aachen.de>
To:	assistenten@informatik.rwth-aachen.de, vortraege@informatik.rwth-aachen.de
CC:	Andreas Klinger <klinger@itsec.rwth-aachen.de>, Birgit Willms <willms@informatik.rwth-aachen.de>, Dennis Fischer <fischer@algo.rwth-aachen.de>

Dear all,

part of the programme of the research training group UnRAVeL is a series of introductory lectures on the topics of „randomness“ and „uncertainty“ in UnRAVeL’s research thrusts algorithms and complexity, verification, logic and languages, and their application scenarios. Each lecture is delivered by one of the researchers involved in UnRAVeL. The main aim is to provide doctoral researchers as well as master students a broad overview of the subjects of UnRAVeL.

This year, 12 UnRAVeL professors will answer the following questions, based on one of their recent scientific results:

• How did you get to this result?
• How did you come up with certain key ideas?
• How did you cope with obstacles on the way? Which ideas you had did not work out?

Following these talks, PhD students will give an informal summary of their doctoral studies within UnRAVeL.

All interested doctoral researchers and master students are invited to attend the UnRAVeL lecture series 2021 and engage in discussions with researchers and doctoral students.

Details information can be found on https://www.unravel.rwth-aachen.de/cms/UnRAVeL/Studium/~pzix/Ringvorlesung-Veranstaltung/?lidx=1

All events take place on Thursdays from 16:30 to 18:00 on Zoom https://rwth.zoom.us/j/96043715437?pwd=U0dRczkyQjRCY21abW13TDNmUHlhUT09

• 01/07/2021 Joost-Pieter Katoen: The Surprises of Probabilistic Termination
• 08/07/2021 Christina Büsing: Robust Minimum Cost Flow Problem Under Consistent Flow Constraints
• 22/07/2021 Ulrike Meyer: Malware Detection
• 29/07/2021 Gerhard Woeginger: Bilevel optimization

We are looking forward to seeing you at the lectures.

Best regards,
Tim Seppelt for the organisation committee