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Understanding the role of randomness when solving locally checkable labeling (LCL) problems in the LOCAL model has been one of the top priorities in the research on distributed graph algorithms in recent years. For LCL problems in…

Data Structures and Algorithms · Computer Science 2025-10-27 Sebastian Brandt , Fabian Kuhn , Zahra Parsaeian

We give practical, efficient algorithms that automatically determine the asymptotic distributed round complexity of a given locally checkable graph problem in the $[\Theta(\log n), \Theta(n)]$ region, in two settings. We present one…

Distributed, Parallel, and Cluster Computing · Computer Science 2022-09-05 Alkida Balliu , Sebastian Brandt , Yi-Jun Chang , Dennis Olivetti , Jan Studený , Jukka Suomela

We present a deterministic $O(\log \log \log n)$-round low-space Massively Parallel Computation (MPC) algorithm for the classical problem of $(\Delta+1)$-coloring on $n$-vertex graphs. In this model, every machine has a sublinear local…

Data Structures and Algorithms · Computer Science 2021-12-14 Artur Czumaj , Peter Davies , Merav Parter

In this work, we give a unifying view of locality in four settings: distributed algorithms, sequential greedy algorithms, dynamic algorithms, and online algorithms. We introduce a new model of computing, called the online-LOCAL model: the…

Data Structures and Algorithms · Computer Science 2022-11-15 Amirreza Akbari , Navid Eslami , Henrik Lievonen , Darya Melnyk , Joona Särkijärvi , Jukka Suomela

Consider a computer network that consists of a path with $n$ nodes. The nodes are labeled with inputs from a constant-sized set, and the task is to find output labels from a constant-sized set subject to some local constraints---more…

Distributed, Parallel, and Cluster Computing · Computer Science 2019-02-19 Alkida Balliu , Sebastian Brandt , Yi-Jun Chang , Dennis Olivetti , Mikaël Rabie , Jukka Suomela

We consider the problem of designing deterministic graph algorithms for the model of Massively Parallel Computation (MPC) that improve with the sparsity of the input graph, as measured by the notion of arboricity. For the problems of…

Data Structures and Algorithms · Computer Science 2023-07-03 Manuela Fischer , Jeff Giliberti , Christoph Grunau

Common definitions of the "standard" LOCAL model tend to be sloppy and even self-contradictory on one point: do the nodes update their state using an arbitrary function or a computable function? So far, this distinction has been safe to…

Distributed, Parallel, and Cluster Computing · Computer Science 2026-02-26 Antonio Cruciani , Avinandan Das , Massimo Equi , Henrik Lievonen , Diep Luong-Le , Augusto Modanese , Jukka Suomela

We present new randomized algorithms that improve the complexity of the classic $(\Delta+1)$-coloring problem, and its generalization $(\Delta+1)$-list-coloring, in three well-studied models of distributed, parallel, and centralized…

Data Structures and Algorithms · Computer Science 2018-11-06 Yi-Jun Chang , Manuela Fischer , Mohsen Ghaffari , Jara Uitto , Yufan Zheng

Recently, studying fundamental graph problems in the \emph{Massively Parallel Computation (MPC) framework, inspired by the MapReduce paradigm, has gained a lot of attention. An assumption common to a vast majority of approaches is to allow…

Data Structures and Algorithms · Computer Science 2019-05-28 Sebastian Brandt , Manuela Fischer , Jara Uitto

While obtaining optimal algorithms for the most important problems in the LOCAL model has been one of the central goals in the area of distributed algorithms since its infancy, tight complexity bounds are elusive for many problems even when…

Distributed, Parallel, and Cluster Computing · Computer Science 2025-05-06 Sebastian Brandt , Ananth Narayanan

For over a decade now we have been witnessing the success of {\em massive parallel computation} (MPC) frameworks, such as MapReduce, Hadoop, Dryad, or Spark. One of the reasons for their success is the fact that these frameworks are able to…

Data Structures and Algorithms · Computer Science 2018-02-02 Artur Czumaj , Jakub Łącki , Aleksander Mądry , Slobodan Mitrović , Krzysztof Onak , Piotr Sankowski

The study of Locally Checkable Labelings (LCLs) has led to a remarkably precise characterization of the distributed time complexities that can occur on bounded-degree trees. A central feature of this complexity landscape is the existence of…

Distributed, Parallel, and Cluster Computing · Computer Science 2026-02-17 Gustav Schmid

By prior work, we have many results related to distributed graph algorithms for problems that can be defined with local constraints; the formal framework used in prior work is locally checkable labeling problems (LCLs), introduced by Naor…

Distributed, Parallel, and Cluster Computing · Computer Science 2024-07-09 Alkida Balliu , Mohsen Ghaffari , Fabian Kuhn , Augusto Modanese , Dennis Olivetti , Mikaël Rabie , Jukka Suomela , Jara Uitto

The Massively Parallel Computation (MPC) model serves as a common abstraction of many modern large-scale parallel computation frameworks and has recently gained a lot of importance, especially in the context of classic graph problems.…

Data Structures and Algorithms · Computer Science 2018-07-20 Sebastian Brandt , Manuela Fischer , Jara Uitto

We study graph connectivity problem in MPC model. On an undirected graph with $n$ nodes and $m$ edges, $O(\log n)$ round connectivity algorithms have been known for over 35 years. However, no algorithms with better complexity bounds were…

Data Structures and Algorithms · Computer Science 2018-05-09 Alexandr Andoni , Clifford Stein , Zhao Song , Zhengyu Wang , Peilin Zhong

We present a complete classification of the deterministic distributed time complexity for a family of graph problems: binary labeling problems in trees. These are locally checkable problems that can be encoded with an alphabet of size two…

Distributed, Parallel, and Cluster Computing · Computer Science 2020-02-19 Alkida Balliu , Sebastian Brandt , Yuval Efron , Juho Hirvonen , Yannic Maus , Dennis Olivetti , Jukka Suomela

We show the first conditionally optimal deterministic algorithm for $3$-coloring forests in the low-space massively parallel computation (MPC) model. Our algorithm runs in $O(\log \log n)$ rounds and uses optimal global space. The best…

Distributed, Parallel, and Cluster Computing · Computer Science 2023-08-02 Christoph Grunau , Rustam Latypov , Yannic Maus , Shreyas Pai , Jara Uitto

We study the minimum spanning tree (MST) problem in the massively parallel computation (MPC) model. Our focus is particularly on the *strictly sublinear* regime of MPC where the space per machine is $O(n^\delta)$. Here $n$ is the number of…

Data Structures and Algorithms · Computer Science 2025-10-10 Amir Azarmehr , Soheil Behnezhad , Rajesh Jayaram , Jakub Łącki , Vahab Mirrokni , Peilin Zhong

Many graph problems are locally checkable: a solution is globally feasible if it looks valid in all constant-radius neighborhoods. This idea is formalized in the concept of locally checkable labelings (LCLs), introduced by Naor and…

Distributed, Parallel, and Cluster Computing · Computer Science 2019-04-12 Alkida Balliu , Juho Hirvonen , Christoph Lenzen , Dennis Olivetti , Jukka Suomela

Miller and Reif's FOCS'85 classic and fundamental tree contraction algorithm is a broadly applicable technique for the parallel solution of a large number of tree problems. Additionally it is also used as an algorithmic design technique for…

Data Structures and Algorithms · Computer Science 2021-11-04 MohammadTaghi Hajiaghayi , Marina Knittel , Hamed Saleh , Hsin-Hao Su