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We describe a new implementation of a parallel Tree-SPH code with the aim to simulate Galaxy Formation and Evolution. The code has been parallelized using SHMEM, a Cray proprietary library to handle communications between the 256 processors…

Astrophysics · Physics 2009-10-31 Cesario Lia , Giovanni Carraro

A common approach in semi-analytic modeling of galaxy formation is to construct Monte Carlo realizations of merger histories of dark matter halos whose masses are sampled from a halo mass function. Both the mass function itself, and the…

Astrophysics of Galaxies · Physics 2017-03-22 Andrew J. Benson

Merge trees are fundamental structures in topological data analysis. Interleaving distance is a widely accepted metric for comparing merge trees, with applications in visualization and scientific computing. While a greedy algorithm exists…

Computational Geometry · Computer Science 2025-09-22 Elena Farahbakhsh Touli , Talha Bin Masood

We introduce the contour process to describe the geometrical properties of merger trees. The contour process produces a one-dimensional object, the contour walk, which is a translation of the merger tree. We portray the contour walk through…

Astrophysics · Physics 2015-05-13 Jaime E. Forero-Romero

We present a new parallel implementation of the PINpointing Orbit Crossing-Collapsed HIerarchical Objects (PINOCCHIO) algorithm, a quick tool, based on Lagrangian Perturbation Theory, for the hierarchical build-up of Dark Matter halos in…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-15 P. Monaco , E. Sefusatti , S. Borgani , M. Crocce , P. Fosalba , R. K. Sheth , T. Theuns

This paper presents a new algorithm for the fast, shared memory, multi-core computation of augmented contour trees on triangulations. In contrast to most existing parallel algorithms our technique computes augmented trees, enabling the full…

Distributed, Parallel, and Cluster Computing · Computer Science 2019-02-14 Charles Gueunet , P. Fortin , J Jomier , J Tierny

Merkle trees have become a widely successful cryptographic data structure. Enabling a vast variety of applications from checking for inconsistencies in databases like Dynamo to essential tools like Git to large scale distributed systems…

Distributed, Parallel, and Cluster Computing · Computer Science 2023-11-30 Anoushk Kharangate

Dark matter halo demographics and assembly histories are a manifestation of cosmological structure formation and have profound implications for the formation and evolution of galaxies. In particular, merger trees provide fundamental input…

Cosmology and Nongalactic Astrophysics · Physics 2024-05-02 L. Y. Aaron Yung , Rachel S. Somerville , Tri Nguyen , Peter Behroozi , Chirag Modi , Jonathan P. Gardner

The effects of spatial correlations of density fluctuations on merger histories of dark matter haloes (so-called `{\it merger trees}') are analysed. We compare the mass functions of dark haloes derived by a new method for calculating merger…

Astrophysics · Physics 2015-06-24 Masahiro Nagashima , Naoteru Gouda

Retrieval-augmented generation (RAG) enhances large language models with external knowledge, and tree-based RAG organizes documents into hierarchical indexes to support queries at multiple granularities. However, existing Tree-RAG methods…

Machine Learning · Computer Science 2026-05-04 Ziwen Zhao , Menglin Yang

This paper presents a study of the specific merger rate as a function of group membership, local environment, and redshift in a very large, $500h^{-1} Mpc$, cosmological N-body simulation, the \textit{Millennium Simulation}. The goal is to…

Cosmology and Nongalactic Astrophysics · Physics 2010-05-07 J. A. Hester , A. Tasitsiomi

The dynamical state and morphological features of galaxies and galaxy clusters, and their high-redshift precursors, are tightly connected with their assembly history, encoding crucial information about the formation and evolution of such…

Cosmology and Nongalactic Astrophysics · Physics 2023-01-10 David Vallés-Pérez , Susana Planelles , Óscar Monllor-Berbegal , Vicent Quilis

Determining the interaction partners among protein/domain families poses hard computational problems, in particular in the presence of paralogous proteins. Available approaches aim to identify interaction partners among protein/domain…

Populations and Evolution · Quantitative Biology 2015-01-14 Iman Hajirasouliha , Alexander Schönhuth , David Juan , Alfonso Valencia , S. Cenk Sahinalp

We describe a methodology to accurately compute halo mass functions, progenitor mass functions, merger rates and merger trees in non-cold dark matter universes using a self-consistent treatment of the generalized extended Press-Schechter…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-11 Andrew J. Benson , Arya Farahi , Shaun Cole , Leonidas A. Moustakas , Adrian Jenkins , Mark Lovell , Rachel Kennedy , John Helly , Carlos Frenk

Dark matter halo merger trees are now routinely extracted from cosmological simulations of structure formation. These trees are frequently used as inputs to semi-analytic models of galaxy formation to provide the backbone within which…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-28 Andrew J. Benson , Stefano Borgani , Gabriella De Lucia , Michael Boylan-Kolchin , Pierluigi Monaco

We describe a simple and fast algorithm for identifying friends-of-friends features and prove its correctness. The algorithm avoids unnecessary expensive neighbor queries, uses minimal memory overhead, and rejects slowdown in high…

Instrumentation and Methods for Astrophysics · Physics 2017-06-02 Yu Feng , Chirag Modi

Retrieval-Augmented Generation (RAG) grounds large language models in external evidence, yet it still falters when answers must be pieced together across semantically distant documents. We close this gap with the Hierarchical Lexical Graph…

We study the impact of merging routines in merge-based sorting algorithms. More precisely, we focus on the galloping routine that TimSort uses to merge monotonic sub-arrays, hereafter called runs, and on the impact on the number of element…

Data Structures and Algorithms · Computer Science 2023-12-04 Elahe Ghasemi , Vincent Jugé , Ghazal Khalighinejad , Helia Yazdanyar

OCTO-TIGER is an astrophysics code to simulate the evolution of self-gravitating and rotat-ing systems of arbitrary geometry based on the fast multipole method, using adaptive mesh refinement. OCTO-TIGER is currently optimised to simulate…

Instrumentation and Methods for Astrophysics · Physics 2021-08-12 Dominic C. Marcello , Sagiv Shiber , Orsola De Marco , Juhan Frank , Geoffrey C. Clayton , Patrick M. Motl , Patrick Diehl , Hartmut Kaiser