Dear all,
this is a reminder for Joost-Pieter Katoen's talk with the title "Can we meet the deadline? Most probably: yes!" taking place today at 12:30 in the B-IT room 5053.2. Please find the details below
--- Abstract ---
Continuous-time Markov chains are used in systems biology, classical performance evaluation,
reliability engineering, physics, and so on. We study a the following analysis problem for CMTCs:
how to compute the probability to reach a certain target state within a given deadline?
Phrased more practically: how likely is it that all substrates have turned into products in a
catalytic chemical reaction within a week? We will show that this probability can be
characterised as a unique solution of a Volterra integral equation system, whose computation
can be reduced to transient analysis of a slightly modified CTMC. We will show why this problem
is of practical relevance, that it can be efficiently solved on CTMCs with millions of states, and
why its natural generalisation to stochastic scheduling problems is hard.
This result was published in 1999, received a test-of-time award in 2022, and forms the
ingredient of many state-of-the-art CTMC tools.
----------------
Part of the programme of the research training group UnRAVeL is a series of lectures on the topics of UnRAVeL’s research thrusts algorithms and complexity, verification, logic and languages, and their application scenarios. Each lecture is given by one of the researchers involved in UnRAVeL.
This years topic is "Biggest Milestones - Research at Its Peak", UnRAVeL professors will present the most important milestone of their respective research.
All interested doctoral researchers and master students are invited to attend the UnRAVeL lecture series 2023 and engage in discussions with researchers and doctoral students.
Note that this is the last lecture for this year! We are looking forward to seeing you today.
Kind regards,
Jan-Christoph for the organisation committee
Dear AI community,
The next Artificial Intelligence Colloquium<https://www.ai.rwth-aachen.de/cms/KI/Das-KI-Center/Aktuelle-Veranstaltungen…> will be a double event: a talk, and a poster session!
On Tuesday, July 18th at 16:00, Prof. Heike Vallery (RWTH Aachen) will give a presentation on “Challenges and opportunities of data-driven learning in physical robots for neurorehabilitation”. After the talk (45 minutes), there will be a Q&A session of 15 minutes.
After the talk and the Q&A, the event will continue with a poster session, which will highlight the latest advancements in various fields of AI. You will have the change of discussing hot AI topics with researchers in the discipline!
Heike Vallery’s talk will be hybrid, and will take place in the Generali Hall of the Super C as well as on Zoom. A free registration<https://vms.zhv.rwth-aachen.de/prod/veranstaltungen/SingleSignOn/Shibboleth…> is required for both in-person and remote participants (please register on our web page<https://www.ai.rwth-aachen.de/go/id/bckstd>). You will receive the link directly in the confirmation email.
The poster session will not be live-streamed.
More information on the event series on the website<https://www.ai.rwth-aachen.de/cms/KI/Das-KI-Center/Aktuelle-Veranstaltungen…>.
Please feel free to forward this information to your research groups or any other interested parties!
The organising team is looking forward to welcoming you on Tuesday next week.
Best regards,
Julia Mann
Dr Julia Mann
Managing Director
______________________________________________
Center for Artificial Intelligence
RWTH Aachen University
Mies-van-der-Rohe-Strasse 15 office: 123
DE-52074 Aachen phone: +49-241-80 20757
Germany
http://www.ai.rwth-aachen.de<http://www.ai.rwth-aachen.de/>
[cid:image001.png@01D9B4DD.8079AC50]
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Zeit: Dienstag, 4. Juli 2023, 13.00 Uhr
Ort: Raum 9222, Gebäude E3, Ahornstr. 55
Referent: Dr. Jakob Bossek
Lehrstuhl Informatik 14
Thema: Tailored Evolutionary Operators for the Multi-Objective Spanning Tree Problem
Abstract:
With this talk I want to introduce myself to the RWTH computer science department.
In the first part I will go into detail on paper recently accepted in the evolutionary computation journal (Bossek & Grimme, 2023) entitled “Tailored Evolutionary Operators for the Multi-Objective Spanning Tree Problem”. The second part will give a broader overview of my research foci and projects in the fields of Evolutionary Optimisation and Automated Artificial Intelligence.
The Minimum Spanning Tree (MST) problem is the challenge of finding a tree in an edge-weighted graph that maintains connectivity of all nodes and has minimal costs among all such trees. The MST problem is a fundamental combinatorial optimisation problem with countless applications, e.g., in the construction of communication networks, medical imaging, or many other areas that range from logistic via graph drawing to power grid network design. The basic single-objective version of the MST problem can be solved efficiently, i.e., in polynomial time, e.g., by Prim’s algorithm. The multi-objective MST (moMST) version though (i.e., multiple weights per edge) is NP-hard and suffers from intractability. Thus, efficient heuristics are needed to approximate the set of optimal trade-off solutions.
Evolutionary Algorithms are randomised search heuristics that are among the most successful when it comes to solving NP-hard multi-objective optimisation problems.
I will present recent work on the design of several highly biased sub-graph-based mutation operators for the moMST problem. In a nutshell, these operators replace (un)connected sub-trees of candidate solutions with locally (Pareto-)optimal sub-trees. The latter (biased) step is realised by applying Kruskal’s single-objective MST algorithm to a weighted sum scalarisation of a sub-graph.
I will detail some runtime complexity results for the introduced operators and demonstrate results that show that the sub-graph based operators beat baseline algorithms from the literature even with severely restricted computational budget in terms of function evaluations on four different classes of complete graphs.
Es laden ein: die Dozentinnen und Dozenten der Informatik
--
Andrea Gibbels, M.A.
Administrative Assistant
Chair for AI Methodology / Lehrstuhl für Methodik der Künstlichen Intelligenz
RWTH Aachen University
E-mail: secret(a)aim.rwth-aachen.de
Phone: +49 241 80 21452
Theaterstr. 35-39
52062 Aachen
Germany
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Zeit: Mittwoch, 12. Juli 2023, 11:00 Uhr
Ort: Informatikzentrum der RWTH Aachen University, Gebäude E3, 2. Etage, Raum 9222
Referent: Benedikt Pago, M.Sc.
Mathematische Grundlagen der Informatik
Thema: Limitations of Choiceless Computation
Abstract:
A central open question in finite model theory asks whether there exists a logic that captures the complexity class PTIME.
Another way of phrasing this is whether every polynomial time algorithm can be efficiently simulated by a choiceless one.
Choiceless computation models operate on finite structures, such as graphs, and can only perform computation steps which are invariant under
the symmetries of the structure. This guarantees that for any two isomorphic input structures, the outcome of the computation is the same -
a property which is typically required of logics.
The quest for a logic for PTIME seeks to develop and analyse logics (i.e. choiceless computation models) of increasing expressive power
within PTIME. One of the most prominent logics that has been suggested and not separated from PTIME within more than 20 years is
Choiceless Polynomial Time (CPT). Obtaining a better understanding of its expressive power is the aim of this thesis;
the focus is on its limitations, since only little is known so far in this regard.
We develop new approaches and techniques towards strong CPT lower bounds. As a promising candidate for separating CPT from PTIME, we propose
the graph isomorphism problem on Cai-Fürer-Immerman (CFI) graphs over unordered hypercubes. The CFI construction is a well-known tool to prove
inexpressibility results for logics. Choiceless polynomial time algorithms are known to exist for certain ordered variants of it but we show
that these fail on unordered CFI graphs. Going further, we study a broader class of CPT-algorithms for this problem and prove that
lower bounds against certain families of symmetric Boolean circuits imply lower bounds for these algorithms. A first lower bound for this kind
of circuits is also presented to demonstrate the feasibility of the approach. It remains open to strengthen it further to get the desired
undefinability result for the CFI problem in CPT.
As an alternative route, we establish a connection to an algebraic proof system called the extended polynomial calculus.
The power of this and similar proof systems is the subject of active research in the field of proof complexity. We show that suitable proof
complexity lower bounds would imply the separation of CPT and PTIME, too.
Es laden ein: die Dozentinnen und Dozenten der Informatik
Dear all,
this is a reminder for Christopher Morris's talk with the title "Weisfeiler and Leman Go Machine Learning: Expressivity and Generalization of Graph Neural Networks" taking place today at 12:30 in the B-IT room 5053.2. Please find the details below
--- Abstract ---
Graph-structured data is prevalent across various domains, such as chemo-
and bioinformatics, image analysis, and social network analysis. As a result,
there has been a surge in the development of machine-learning methods
explicitly tailored to graphs. Among these methods, (message-passing) graph
neural networks (GNNs) have emerged as the dominant paradigm. Despite
their practical success, GNNs' capabilities and limitations are understood to a
lesser extent. In this talk, we survey results connecting GNNs' expressive power
and generalization abilities to a simple heuristic for the graph isomorphism
problem---the Weisfeiler-Leman algorithm.
----------------
Part of the programme of the research training group UnRAVeL is a series of lectures on the topics of UnRAVeL’s research thrusts algorithms and complexity, verification, logic and languages, and their application scenarios. Each lecture is given by one of the researchers involved in UnRAVeL.
This years topic is "Biggest Milestones - Research at Its Peak", UnRAVeL professors will present the most important milestone of their respective research.
All interested doctoral researchers and master students are invited to attend the UnRAVeL lecture series 2023 and engage in discussions with researchers and doctoral students.
Note that next week there is no talk and then we have the last talk of this year's survey lecture from Joost-Pieter Katoen with the title "Can we meet the deadline? Most probably: yes!"
We are looking forward to seeing you at the lectures.
Kind regards,
Jan-Christoph for the organisation committee
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Zeit: Freitag, 7. Juli 2023, 10:00 Uhr
Ort: Informatikzentrum der RWTH Aachen University, Gebäude E3, 2. Etage, Raum 9222
Referentin: Jip Spel, M.Sc.
Lehrstuhl Informatik 2
Thema:Monotonicity in Markov Models
Abstract:
Many systems exhibit probabilistic behavior, such as randomized protocols, communication protocols, or biological systems.
Probabilistic model checking is a common way to analyze these type of systems. We often model these systems as Markov models
and check them against a specification typically given in a probabilistic extension of LTL or CTL. One of the main goals is
to analyze the probability to reach or the expected total reward upon reaching a set of target states. When checking for these
properties, we assume probabilities to be fixed constants. In practice, however, these probabilities are often not fixed but
bounded to a given interval. Moreover, these probabilities can be dependent on other probabilities. Therefore, we consider
parametric Markov models, in which the probabilities are given symbolically by rational functions over parameters.
Common problems are the almost-optimal synthesis problem (i.e., finding a parameter instantiation such that the expected
total reward is 𝜀-close to the real unknown optimal expected total reward) and the feasibility problem (i.e., finding parameter
instantiations that reach the target with at least a given probability or expected total reward).
In this talk, we introduce and define monotonicity of parametric Markov models. We observe that many systems are monotonic
in one or more parameters, e.g., if we increase the probability of a parameter, the expected total reward also increases.
We show how we can algorithmically find monotonicity and use this to, e.g., improve existing techniques like parameter lifting
to solve the almost-optimal synthesis problem. We experimentally show that we significantly improve the time to determine
almost-optimal synthesis. Furthermore, we consider the well-known gradient descent method to deal with the feasibility problem.
We show that our implementation of the gradient descent method (as implemented in the modelchecker STORM) outperforms particle
swarm optimization and quadratically-constrained quadratic programming and performs akin to sequential convex programming.
Finally, we introduce parametric probabilistic timed automata (pPTAs). We extend probabilistic timed automata (PTAs) to pPTAs,
such that the probabilities can be unknown. We show that some techniques to reduce PTAs to MDPs also work for pPTAs.
An implementation of this reduction for pPTAs is available in the Modest Toolset.
Es laden ein: die Dozentinnen und Dozenten der Informatik
--
________________________________________
Birgit Willms
Lehrstuhl Informatik 2
Koordinierung GRK UnRAVeL
RWTH Aachen University
Ahornstraße 55
D-52074 Aachen
Tel.: +49 (0)241 80 21209
E-Mail:willms@cs.rwth-aachen.de
www:www.unravel.rwth-aachen.de/
Dear all,
this is a reminder for Gerhard Lakemeyer's talk with the title "The Situation Calculus as Lingua Franca for Reasoning about Action" taking place today at 12:30 in the B-IT room 5053.2. Please find the details below
--- Abstract ---
The Situation Calculus is almost as old as the field of Artificial Intelligence, and thanks
to the groundbreaking work by the late Ray Reiter it is still one of the most used and
best understood logical formalisms for reasoning about action and change. In this lecture
I will introduce the modern form of the situation calculus due to Ray Reiter and go over
extensions such as probabilistic actions and the action programming language
Golog built on top of the situation calculus.
----------------
Part of the programme of the research training group UnRAVeL is a series of lectures on the topics of UnRAVeL’s research thrusts algorithms and complexity, verification, logic and languages, and their application scenarios. Each lecture is given by one of the researchers involved in UnRAVeL.
This years topic is "Biggest Milestones - Research at Its Peak", UnRAVeL professors will present the most important milestone of their respective research.
All interested doctoral researchers and master students are invited to attend the UnRAVeL lecture series 2023 and engage in discussions with researchers and doctoral students.
Next week we have a talk from Christopher Morris with the title "Weisfeiler and Leman Go Machine Learning: Expressivity and Generalization of Graph Neural Networks"
We are looking forward to seeing you at the lectures.
Kind regards,
Jan-Christoph for the organisation committee
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Zeit: Freitag, 23. Juni 2023,14.00 Uhr
Ort: Kopernikusstrasse 6, 52704 Aachen, Seminarraum 003
Referent: Dipl. Inf. Alper Yegenoglu
SDL Neuroscience, Jülich Supercomputing Centre,
Forschungszentrum Jülich,
Institute of Geometry and Applied Mathematics &
Informatik i3, RWTH Aachen
Thema: Gradient-Free Optimization of Artificial and Biological Networks
using Learning to Learn
Abstract:
The quest to understand intelligence, learning, decision-making, and
memory in humans has been a longstanding endeavor in neuroscience. Our
brain comprises networks of neurons and other cells, but it remains
unclear how these networks are trained to solve specific tasks. In the
field of machine learning and artificial intelligence, neural networks
are commonly optimized using gradient descent and backpropagation.
However, applying this optimization strategy to biological spiking
networks (SNNs) presents challenges due to the binary communication
scheme via spikes among neurons.
In my work, I propose gradient-free optimization techniques that can be
directly applied to both artificial and biological neural networks. I
utilize metaheuristics such as genetic algorithms and the ensemble
Kalman Filter (EnKF) to optimize network parameters and train them to
solve specific tasks. This optimization is integrated into the concept
of learning to learn (L2L), which involves a two-loop optimization
procedure. In the inner loop, the algorithm or network is trained on a
set of tasks, while in the outer loop, the hyperparameters and
parameters are optimized. Initially, I apply the EnKF to a convolutional
neural network, achieving high accuracy in digit classification. I then
extend this optimization approach to a spiking reservoir network within
the Python based L2L-framework. Analyzing connection weights and the
EnKF's covariance matrix offers insights into the optimization process.I
further adapt the optimization by integrating the EnKF into the inner
loop and update hyperparameters using a genetic algorithm. This
automated approach suggests alternative configurations, in contrast to a
manual parameter tuning. Additionally, I present a simulation where SNNs
guide an ant colony in food foraging, resulting in emergent
self-coordination and self-organization. I employ correlation analysis
methods to understand the ants' behavior.
Through my work, I demonstrate the application of gradient-free
optimization techniques utilizing learning to learn. I highlight their
effectiveness in optimizing biological and artificial neural networks.
Es laden ein: die Dozentinnen und Dozenten der Informatik
--
Prof. Dr. Abigail Morrison
IAS-6 / INM-6 / SimLab Neuroscience
Jülich Research Center
&
Computer Science 3 - Software Engineering
RWTH Aachen
http://www.fz-juelich.de/inm/inm-6http://www.fz-juelich.de/ias/jsc/slnshttp://www.se-rwth.de
Office: +49 2428 8097504
Fax # : +49 2461 61-9460
Pronouns: she/her
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Forschungszentrum Juelich GmbH
52425 Juelich
Sitz der Gesellschaft: Juelich
Eingetragen im Handelsregister des Amtsgerichts Dueren Nr. HR B 3498
Vorsitzender des Aufsichtsrats: MinDir Stefan Müller
Geschaeftsfuehrung: Prof. Dr.-Ing. Wolfgang Marquardt (Vorsitzender),
Karsten Beneke (stellv. Vorsitzender), Dr. Ir. Pieter Jansens,
Prof. Dr. Astrid Lambrecht, Prof. Dr. Frauke Melchior
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Zeit: Freitag, 30. Juni 2023, 16.30 Uhr
Ort: Raum 2202 (HBau, 2. Stock), Ahornstr. 55
Referent: Maximilian Kloock, M.Sc. RWTH
Informatik 11 - Embedded Software
Thema: Synchronization-Based Cooperative Trajectory Planning of Networked Vehicles
Abstract:
Centralized decision-making for a Networked Control System (NCS) suffers from a
high computational burden on the planning agent. Distributed agents, which compute
distributed decision-making, increase the computational performance of the NCS. In
distributed decision-making, agents consider a subset of all agents in their planning.
Due to only local system knowledge of the agents, these local plans are potentially
inconsistent with the local plans of other agents. Such an inconsistency may lead to the
infeasibility of local plans. This thesis proposes an algorithm that utilizes synchronization
methods to achieve consistency of local plans in distributed decision-making. The
algorithm enables fast computations due to parallel decision-making and achieves feasible
decisions. The parallel and iterative algorithm alternates two steps: local planning and
global synchronization. In the local planning step, the agents parallelly compute local
plans. Subsequently, consistency of the local plans across agents is achieved using global
synchronization. The globally synchronized plans act as reference decisions for the local
planning step in the next iteration. In each iteration, the local planning guarantees
locally feasible plans, while the synchronization guarantees globally consistent plans.
The parallel algorithm converges to globally feasible decisions if the coupling topology
is feasible. This thesis introduces requirements for the coupling topology to achieve
convergence to globally feasible decisions and proposes a centralized and a distributed
method to generate coupling topologies that fulfill these requirements. The centralized
coupling topology generation method uses its knowledge about all agents to generate
time-invariant coupling topologies in a greedy manner. The distributed coupling topology
generation method generates time-variant coupling topologies using game-theory.
In order to demonstrate the distributed decision-making algorithm in experiments, this
thesis proposes an architecture for networked control systems that achieves deterministic
and reproducible experiments, even with non-deterministic computation and communication
times. The Cyber-Physical Mobility Lab (CPM Lab), an open-source and remotely
accessible platform for networked and autonomous vehicles, implements this architecture.
Moreover, the CPM Lab provides a suitable interface for rapid prototyping with seamless
simulations and experiments.
This thesis demonstrates the complete pipeline from uncoupled agents to globally
feasible solutions. The distributed decision-making uses a Model Predictive Control
(MPC) framework. The evaluation of this thesis uses the CPM Lab as an evaluation
platform to evaluate the Distributed MPC (DMPC) algorithm using the coupling topologies
generated from the centralized and distributed generation methods. The evaluation
shows that the proposed DMPC algorithm achieves feasible solutions while requiring
lower computation times and lower communication demands than Centralized MPC
(CMPC). The resulting trajectories show only small deviations from the globally optimal
trajectories generated by CMPC.
Es laden ein: die Dozentinnen und Dozenten der Informatik
Dear colleagues and students,
On Friday 23.06, Silvia Sellán from the Dynamic Graphics Project at the
University of Toronto will be visiting us to hold a talk about her
recent cutting-edge research on stochastic surface reconstruction for
recovering shapes from 3D point clouds. Silvia has a proven track record
of publishing innovative research at the top venues of her field, and we
in the Computer Animation group are thrilled to have her visit. Details
below!
*/When/*: Friday 23.06, 14:00-15:00.
*/Where/*:
Seminar Room 118, Building E3, Floor 1
Mies-van-der-Rohe-Straße, 52074 Aachen
(same floor as the Computer Graphics group)
/*Title*/: Uncertain Surface Reconstruction
*/Abstract/*: We propose a method to introduce uncertainty to the
surface reconstruction problem. Specifically, we introduce a statistical
extension of the classic Poisson Surface Reconstruction algorithm for
recovering shapes from 3D point clouds. Instead of outputting an
implicit function, we represent the reconstructed shape as a modified
Gaussian Process, which allows us to conduct statistical queries (e.g.,
the likelihood of a point in space being on the surface or inside a
solid). We show that this perspective improves PSR's integration into
the online scanning process, broadens its application realm, and opens
the door to other lines of research such as applying task-specific priors.
/*Bio*/: Silvia is a fourth year Computer Science PhD student at the
University of Toronto. She is advised by Alec Jacobson and working in
Computer Graphics and Geometry Processing. She is a Vanier Doctoral
Scholar, an Adobe Research Fellow and the winner of the 2021 University
of Toronto Arts & Science Dean’s Doctoral Excellence Scholarship. She
has interned twice at Adobe Research and twice at the Fields Institute
of Mathematics. She is also a founder and organizer of the Toronto
Geometry Colloquium and a member of WiGRAPH. She is currently looking to
survey potential future postdoc and faculty positions, starting Fall 2024.
Looking forward to seeing curious researchers and students alike next
Friday!
Sincerely,
Andreas Longva, Msc.
Computer Animation group
Visual Computing Institute