iiinova — where your digital self keeps evolving

Juha Harviainen @juhahar.bsky.social · 07/10/2026

The HIIT Open programming contest is returning on 21 Nov and the registration is now open. Algorithmic NCPC-style problem solving in teams of 1–3 people, organized at the premises of Aalto University, and everyone's welcome to participate! open.hiit.fi

open.hiit.fi

HIIT Open 2026 Programming Contest

HIIT Open 2026 Programming Contest, Saturday, 21 Nov 2026, Otaniemi, Espoo, Finland.

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Juha Harviainen @juhahar.bsky.social · 10/09/2026

I'm happy to announce the Parameterized Algorithms and Computational Experiments (PACE) Challenge of 2027—revealed in IPEC '26—with the goal of designing practical algorithms for finding k-paths: pacechallenge.org/2027/

pacechallenge.org

PACE 2027 · PACE Challenge

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Reposted by Juha Harviainen

Tieteentekijät @tieteentekijat.bsky.social · 25/06/2026

Arvoisa sosiaali- ja terveysministeri Wille Rydman. Poliitikkojen tehtävä ei ole ohjailla, mitä saa tutkia. Heidän tehtävänsä on varmistaa, että tiede saa riittävät ja vakaat resurssit. tieteentekijat.fi/poliittinen-...

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Juha Harviainen @juhahar.bsky.social · 01/06/2026

Two papers accepted to UAI 2026: [Oral] "Scaling Up Bayesian DAG Sampling" with Daniele Nikzad, Alexander Zhilkin, Jack Kuipers, Giusi Moffa, and Mikko Koivisto [Poster] "Learning Bayesian and Markov Networks with an Unreliable Oracle" with Pekka Parviainen and Vidya Sagar Sharma

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Juha Harviainen @juhahar.bsky.social · 30/04/2026

Accepted to ICML 2026: "Exact and Approximate Algorithms for Polytree Learning" with Frank Sommer and Manuel Sorge. Polytrees are Bayes nets that encode causal relations as trees but learning their structure is NP-hard. We speed up SOTA on exact algorithms and give several approximation algorithms.

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Jukka Suomela @jukkasuomela.fi · 14/04/2026

The Baltic Olympiad in Informatics 2026 starting tomorrow! Organized at the Aalto University campus in Otaniemi, in collaboration with Aalto University, University of Helsinki, Helsinki Institute for Information Technology HIIT, and MAOL. boi2026.cses.fi

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Juha Harviainen @juhahar.bsky.social · 03/04/2026

Two new publications (preprints linked): - "Scalable computation of ultrabubbles in pangenomes by orienting bidirected graphs" was accepted to ISMB 2026 www.biorxiv.org/content/10.6... - "Graph Reconstruction with a Connected Components Oracle" was accepted to WG 2026 arxiv.org/abs/2509.05002

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Reposted by Juha Harviainen

Christian Wolf @chriswolfvision.bsky.social · 27/11/2025

This is by a large margin the most serious problem and mistake in conference peer review I have seen in my career. Apparently a many people were aware of this and many could find out who their reviewers were. This probably has created a large number of unnecessary enmities. @iclr-conf.bsky.social

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Reposted by Juha Harviainen

Jukka Suomela @jukkasuomela.fi · 08/11/2025

HIIT Open 2025 programming contest has started!

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Reposted by Juha Harviainen

Jukka Suomela @jukkasuomela.fi · 06/11/2025

HIIT Open 2025 programming contest coming on Saturday, 45 contestants in 20 teams competing at Aalto University! open.hiit.fi

open.hiit.fi

HIIT Open 2025 Programming Contest

HIIT Open 2025 Programming Contest, Saturday, 8 Nov 2025, Otaniemi, Espoo, Finland.

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Juha Harviainen @juhahar.bsky.social · 30/10/2025

New preprint on arXiv: arxiv.org/abs/2510.25254 We propose two novel improvements to MCMC for Bayesian network structures by speeding up the basic moves and pruning less relevant parent sets, both resulting in one to three orders of magnitude improvements in the running time.

arxiv.org

Scaling Up Bayesian DAG Sampling

Bayesian inference of Bayesian network structures is often performed by sampling directed acyclic graphs along an appropriately constructed Markov chain. We present two techniques to improve sampling....

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Reposted by Juha Harviainen

algorithms.fi @algorithms.fi · 06/10/2025

New papers from the HALT community: 2 x SODA 2025, 2 x NeurIPS 2025, 3 x Asiacrypt 2025, and more! algorithms.fi/publications/

algorithms.fi

HALT: Publications

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Juha Harviainen @juhahar.bsky.social · 22/09/2025

Our follow-up paper to this, "Improving Decision Trees through the Lens of Parameterized Local Search", with Sommer and Sorge, got accepted to NeurIPS '25! We study the parameterized complexity of improving decision trees by modifying multiple internal nodes simultaneously to avoid local optimas.

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Reposted by Juha Harviainen

algorithms.fi @algorithms.fi · 05/09/2025

Most of the presentation slides from Theory Days now available online: algorithms.fi/theory-days-...

algorithms.fi

Helsinki Algorithms & Theory Days

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Reposted by Juha Harviainen

algorithms.fi @algorithms.fi · 17/08/2025

Helsinki Algorithms & Theory Days program is now available online: algorithms.fi/theory-days-...

algorithms.fi

Helsinki Algorithms & Theory Days

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algorithms.fi @algorithms.fi · 24/07/2025

Helsinki Algorithms & Theory Days on 28–29 August, 2025, keynote talk by Andris Ambainis algorithms.fi/theory-days-...

algorithms.fi

Helsinki Algorithms & Theory Days

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Juha Harviainen @juhahar.bsky.social · 03/06/2025

Preprint now available on arXiv: arxiv.org/abs/2305.19673

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Juha Harviainen @juhahar.bsky.social · 07/05/2025

In collaboration with Kseniya Rychkova and Mikko Koivisto, our paper "Quantum Speedups for Bayesian Network Structure Learning" was accepted to UAI 2025. We show the time complexity of classical algorithms for structure learning to be presumably optimal and give better quantum algorithms.

A directed acyclic graph where the labels of the nodes are elements of the universe and their subsets.

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Juha Harviainen @juhahar.bsky.social · 02/05/2025

With colleagues from TU Wien—Frank Sommer, Manuel Sorge, and @szeider.bsky.social—our paper "Optimal Decision Tree Pruning Revisited: Algorithms and Complexity" got accepted to ICML. The paper provides a comprehensive study of parameterized complexity of pruning decision trees to reduce overfitting.

Illustration of two pruning operations: one where the whole subtree is replaced by a leaf and the other where some subtree is raised to replace its parent.

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Juha Harviainen @juhahar.bsky.social · 25/04/2025

The paper is now available in AISTATS'25 proceedings: proceedings.mlr.press/v258/harviai...

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Reposted by Juha Harviainen

algorithms.fi @algorithms.fi · 14/03/2025

Today's Frontier Friday material here: algorithms.fi/frontier-fri...

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Reposted by Juha Harviainen

algorithms.fi @algorithms.fi · 19/02/2025

Information on HIIT Frontier Friday now here, next meeting: 14 Mar 2025 algorithms.fi/frontier-fri...

algorithms.fi

HIIT Frontier Friday

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Juha Harviainen @juhahar.bsky.social · 23/01/2025

Our paper "On Tractability of Learning Bayesian Networks with Ancestral Constraints" with Pekka Parviainen was accepted to AISTATS'25 🎉 The paper studies parameterized complexity of structure learning for varying constraints when we can say something about the order of any set of nodes larger than k

Several directed acyclic graphs whose vertices are partitioned into layers, which are used in dynamic programming.

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